Note: The quantitative elements of this post have now been revised significantly.

Followup to: You Be the Jury: Survey on a Current Event

All three of them clearly killed her. The jury clearly believed so as well which strengthens my argument. They spent months examining the case, so the idea that a few minutes of internet research makes [other commenters] certain they're wrong seems laughable

- lordweiner27, commenting on my previous post

The short answer: it's very much like how a few minutes of philosophical reflection trump a few millennia of human cultural tradition.

Wielding the Sword of Bayes -- or for that matter the Razor of Occam -- requires courage and a certain kind of ruthlessness. You have to be willing to cut your way through vast quantities of noise and focus in like a laser on the signal.

But the tools of rationality are extremely powerful if you know how to use them.

Rationality is not easy for humans. Our brains were optimized to arrive at correct conclusions about the world only insofar as that was a necessary byproduct of being optimized to pass the genetic material that made them on to the next generation. If you've been reading Less Wrong for any significant length of time, you probably know this by now. In fact, around here this is almost a banality -- a cached thought. "We get it," you may be tempted to say. "So stop signaling your tribal allegiance to this website and move on to some new, nontrivial meta-insight."

But this is one of those things that truly do bear repeating, over and over again, almost at every opportunity. You really can't hear it enough. It has consequences, you see. The most important of which is: if you only do what feels epistemically "natural" all the time, you're going to be, well, wrong. And probably not just "sooner or later", either. Chances are, you're going to be wrong quite a lot.

To borrow a Yudkowskian turn of phrase: if you don't ever -- or indeed often -- find yourself needing to zig when, not only other people, but all kinds of internal "voices" in your mind are loudly shouting for you to zag, then you're either a native rationalist -- a born Bayesian, who should perhaps be deducing general relativity from the fall of an apple any minute now -- or else you're simply not trying hard enough.    

Oh, and another one of those consequences of humans' not being instinctively rational?

Two intelligent young people with previously bright futures, named Amanda and Raffaele, are now seven days into spending the next quarter-century of their lives behind bars for a crime they almost certainly did not commit.

"Almost certainly" really doesn't quite capture it. In my previous post I asked readers to assign probabilities to the following propositions:

1. Amanda Knox is guilty (of killing Meredith Kercher)
2. Raffaele Sollecito is guilty (of killing Meredith Kercher)
3. Rudy Guédé is guilty (of killing Meredith Kercher)

I also asked them to guess at how closely they thought their estimates would match mine.

Well, for comparison, here are mine (revised):

1. Negligible. Small. Hardly different from the prior, which is dominated by the probability that someone in whatever reference class you would have put Amanda into on January 1, 2007 would commit murder within twelve months. Something on the order of 0.001 0.01 or 0.1 at most.  
2. Ditto.
3. About as high as the other two numbers are low. 0.999 0.99 as a (probably weak) lower bound.

Yes, you read that correctly. In my opinion, there is for all intents and purposes zero Bayesian evidence that Amanda and Raffaele are guilty. Needless to say, this differs markedly from the consensus of the jury in Perugia, Italy. 

How could this be?

Am I really suggesting that the estimates of eight jurors -- among whom two professional judges -- who heard the case for a year, along with something like 60% of the Italian public and probably half the Internet (and a significantly larger fraction of the non-American Internet), could be off by a minimum of three orders of magnitude (probably significantly more) such a large amount? That most other people (including most commenters on my last post) are off by no fewer than two?

Well, dear reader, before getting too incredulous, consider this. How about averaging the probabilities all those folks would assign to the proposition that Jesus of Nazareth rose from the dead, and calling that number x. Meanwhile, let y be the correct rational probability that Jesus rose from the dead, given the information available to us.

How big do you suppose the ratio x/y is?

Anyone want to take a stab at guessing the logarithm of that number?

Compared to the probability that Jesus rose from the dead, my estimate of Amanda Knox's culpability makes it look like I think she's as guilty as sin itself.

And that, of course, is just the central one of many sub-claims of the hugely complex yet widely believed proposition that Christianity is true. There are any number of other equally unlikely assertions that Amanda would have heard at mass on the day after being found guilty of killing her new friend Meredith (source in Italian) -- assertions that are assigned non-negligible probability by no fewer than a couple billion of the Earth's human inhabitants.

I say this by way of preamble: be very wary of trusting in the rationality of your fellow humans, when you have serious reasons to doubt their conclusions.

The Lawfulness of Murder: Inference Proceeds Backward, from Crime to Suspect

We live in a lawful universe. Every event that happens in this world -- including human actions and thoughts -- is ultimately governed by the laws of physics, which are exceptionless. 

Murder may be highly illegal, but from the standpoint of physics, it's as lawful as everything else. Every physical interaction, including a homicide, leaves traces -- changes in the environment that constitute information about what took place.

Such information, however, is -- crucially -- local. The further away in space and time you move from the event, the less entanglement there is between your environment and that of the event, and thus the more difficult it is to make legitimate inferences about the event. The signal-to-noise ratio decreases dramatically as you move away in causal distance from the event. After all, the hypothesis space of possible causal chains of length n leading to the event increases exponentially in n.

By far the most important evidence in a murder investigation will therefore be the evidence that is the closest to the crime itself -- evidence on and around the victim, as well as details stored in the brains of people who were present during the act. Less important will be evidence obtained from persons and objects a short distance away from the crime scene; and the importance decays rapidly from there as you move further out.

It follows that you cannot possibly expect to reliably arrive at the correct answer by starting a few steps removed in the causal chain, say with a person you find "suspicious" for some reason, and working forward to come up with a plausible scenario for how the crime was committed. That would be privileging the hypothesis. Instead, you have to start from the actual crime scene, or as close to it as you can get, and work backward, letting yourself be blown by the winds of evidence toward one or more possible suspects.

In the Meredith Kercher case, the winds of evidence blow with something like hurricane force in the direction of Rudy Guédé. After the murder, Kercher's bedroom was filled with evidence of Guédé's presence; his DNA was found not only on top of but actually inside her body. That's about as close to the crime as it gets. At the same time, no remotely similarly incriminating genetic material was found from anyone else -- in particular, there were no traces of the presence of either Amanda Knox or Raffaele Sollecito in the room (and no, the supposed Sollecito DNA on Meredith's bra clasp just plain does not count -- nor, while we're at it, do the 100 picograms [about one human cell's worth] of DNA from Meredith allegedly on the tip of a knife handled by Knox, found at Sollecito's apartment after the two were already suspects; these two things constituting pretty much the entirety of the physical "evidence" against the couple).

If, up to this point, the police had reasons to be suspicious of Knox, Sollecito, and Guédé, they should have cleared Knox and Sollecito at once upon the discovery that Guédé -- who, by the way, was the only one to have fled the country after the crime -- was the one whom the DNA matched. Unless, that is, Knox and Sollecito were specifically implicated by Guédé; after all, maybe Knox and Sollecito didn't actually kill the victim, but instead maybe they paid Guédé to do so, or were otherwise involved in a conspiracy with him. But the prior probabilities of such scenarios are low, even in general -- to say nothing of the case of Knox and Sollecito specifically, who, tabloid press to the contrary, are known to have had utterly benign dispositions prior to these events, and no reason to want Meredith Kercher dead.

If Amanda Knox and Raffaele Sollecito were to be in investigators' thoughts at all, they had to get there via Guédé -- because otherwise the hypothesis (a priori unlikely) of their having had homicidal intent toward Kercher would be entirely superfluous in explaining the chain of events that led to her death.  The trail of evidence had led to Guédé, and therefore necessarily had to proceed from him; to follow any other path would be to fatally sidetrack the investigation, and virtually to guarantee serious -- very serious -- error. Which is exactly what happened.

There was in fact no inferential path from Guédé to Knox or Sollecito. He never implicated either of the two until long after the event; around the time of his apprehension, he specifically denied that Knox had been in the room. Meanwhile, it remains entirely unclear that he and Sollecito had ever even met.

The hypotheses of Knox's and Sollecito's guilt are thus seen to be completely unnecessary, doing no explanatory work with respect to Kercher's death. They are nothing but extremely burdensome details.  

Epistemic Ruthlessness: Following the Strong Signal

All of the "evidence" you've heard against Knox and Sollecito -- the changing stories, suspicious behavior, short phone calls, washing machine rumors, etc. -- is, quite literally, just noise.

But it sounds so suspicious, you say. Who places a three-second phone call? 

As humans, we are programmed to think that the most important kinds of facts about the world are mental and social -- facts about what humans are thinking and planning, particularly as regards to other humans. This explains why some people are capable of wondering whether the presence of (only) Rudy Guédé's DNA in and on Meredith's body should be balanced against the possibilty that Meredith may have been annoyed at Amanda for bringing home boyfriends and occasionally forgetting to flush the toilet -- that might have led to resentment on Amanda's part, you see.

That's an extreme example, of course -- certainly no one here fell into that kind of trap. But at least one of the most thoughtful commenters was severely bothered by the length of Amanda's phone calls to Meredith. As -- I'll confess -- was I, for a minute or two.

I don't know why Amanda wouldn't have waited longer for Meredith to pick up. (For what it's worth, I myself have sometimes, in a state of nervousness, dialed someone's number, quickly changed my mind, then dialed again a short time later.) But -- as counterintuitive as it may seem -- it doesn't matter. The error here is even asking a question about Amanda's motivations when you haven't established an evidentiary (and that means physical) trail leading from Meredith's body to Amanda's brain. (Or even more to the point, when you have established a trail that led decisively elsewhere.)

Maybe it's "unlikely" that Amanda would have behaved this way if she were innocent. But is the degree of improbabilty here anything like the improbability of her having participated in a sex-orgy-killing without leaving a single piece of physical evidence behind? While someone else left all kinds of traces? When you had no reason to suspect her at all without looking a good distance outside Meredith's room, far away from the important evidence?

It's not even remotely comparable. 

Think about what you're doing here: you are invoking the hypothesis that Amanda Knox is guilty of murder in order to explain the fact that she hung up the phone after three seconds. (Remember, the evidence against Guédé is such that the hypothesis of her guilt is superfluous -- not needed -- in explaining the death of Meredith Kercher!)

Maybe that's not quite as bad as invoking a superintelligent deity in order to explain life on Earth; but it's the same kind of mistake: explaining a strange thing by postulating a far, far stranger thing.

"But come on," says a voice in your head. "Does this really sound like the behavior of an innocent person?"

You have to shut that voice out. Ruthlessly. Because it has no way of knowing. That voice is designed to assess the motivations of members of an ancestral hunter-gather band. At best, it may have the ability to distinguish the correct murderer from between 2 and 100 possibilities -- 6 or 7 bits of inferential power on the absolute best of days. That may have worked in hunter-gatherer times, before more-closely-causally-linked physical evidence could hope to be evaluated. (Or maybe not -- but at least it got the genes passed on.)

DNA analysis, in contrast, has in principle the ability to uniquely identify a single individual from among the entire human species (depending on how much of the genome is looked at; also ignoring identical twins, etc.) -- that's more like 30-odd bits of inferential power. In terms of epistemic technology, we're talking about something like the difference in locomotive efficacy between a horsedrawn carriage and the Starship Enterprise. Our ancestral environment just plain did not equip our knowledge-gathering intuitions with the ability to handle weapons this powerful.

We're talking about the kind of power that allows us to reduce what was formerly a question of human social psychology -- who made the decision to kill Meredith? -- to one of physics. (Or chemistry, at any rate.)

But our minds don't naturally think in terms of physics and chemistry. From an intuitive point of view, the equations of those subjects are foreign; whereas "X did Y because he/she wanted Z" is familiar. This is why it's so difficult for people to intuitively appreciate that all of the chatter about Amanda's "suspicious behavior" with various convincing-sounding narratives put forth by the prosecution is totally and utterly drowned out to oblivion by the sheer strength of the DNA signal pointing to Guédé alone.

This rationalist skill of following the strong signal -- mercilessly blocking out noise -- might be considered an epistemic analog of the instrumental "shut up and multiply": when much is at stake, you have to be willing to jettison your intuitive feelings in favor of cold, hard, abstract calculation.

In this case, that means, among other things, thinking in terms of how much explanatory work is done by the various hypotheses, rather than how suspicious Amanda and Raffaele seem

Conclusion: The Amanda Knox Test

I chose the title of this post because the parallel structure made it sound nice. But actually, I think an hour is a pretty weak upper bound on the amount of time a skilled rationalist should need to arrive at the correct judgment in this case.

The fact is that what this comes down to is an utterly straightforward application of Occam's Razor. The complexity penalty on the prosecution's theory of the crime is enormous; the evidence in its favor had better be overwhelming. But instead, what we find is that the evidence from the scene -- the most important sort of evidence by a huge margin -- points with literally superhuman strength toward a mundane, even typical, homicide scenario. To even consider theories not directly suggested by this evidence is to engage in hypothesis privileging to the extreme.

So let me say it now, in case there was any doubt: the prosecution of Amanda Knox and Raffaele Sollecito, culminating in last week's jury verdict -- which apparently was unanimous, though it didn't need to be under Italian rules -- represents nothing but one more gigantic, disastrous rationality failure on the part of our species.

How did Less Wrong do by comparison? The average estimated probability of Amanda Knox's guilt was 0.35 (thanks to Yvain for doing the calculation). It's pretty reasonable to assume the figure for Raffaele Sollecito would be similar. While not particularly flattering to the defendants (how would you like to be told that there's a 35% chance you're a murderer?), that number makes it obvious we would have voted to acquit. (If a 65% chance that they didn't do it doesn't constitute  "reasonable doubt" that they did...)

The commenters whose estimates were closest to mine -- and, therefore, to the correct answer, in my view -- were Daniel Burfoot and jenmarie. Congratulations to them. (But even they were off by a factor of at least ten!)

In general, most folks went in the right direction, but, as Eliezer noted, were far too underconfident -- evidently the result of an exorbitant level of trust in juries, at least in part. But people here were also widely making the same object-level mistake as (presumably) the jury: vastly overestimating the importance of "psychological" evidence, such as Knox's inconsistencies at the police station, as compared to "physical" evidence (only Guédé's DNA in the room).

One thing that was interesting and rather encouraging, however, is the amount of updating people did after reading others' comments -- most of it in the right direction (toward innocence).

[EDIT: After reading comments on this post, I have done some updating of my own. I now think I failed to adequately consider the possibility of my own overconfidence. This was pretty stupid of me, since it meant that the focus was taken away from the actual arguments in this post, and basically toward the issue of whether 0.001 can possibly be a rational estimate for anything you read about on the Internet. The qualitative reasoning of this post, of course, stands. Also, the focus of my accusations of irrationality was not primarily the LW community as reflected in my previous post; I actually think we did a pretty good job of coming to the right conclusion given the information provided -- and as others have noted, the levelheadedness with which we did so was impressive.]

For most frequenters of this forum, where many of us regularly speak in terms of trying to save the human species from various global catastrophic risks, a case like this may not seem to have very many grand implications, beyond serving as yet another example of how basic principles of rationality such as Occam's Razor are incredibly difficult for people to grasp on an intuitive level. But it does catch the attention of someone like me, who takes an interest in less-commonly-thought-about forms of human suffering.

The next time I find myself discussing the "hard problem of consciousness", thinking in vivid detail about the spectrum of human experience and wondering what it's like to be a bat, I am going to remember -- whether I say so or not -- that there is most definitely something it's like to be Amanda Knox in the moments following the announcement of that verdict: when you've just learned that, instead of heading back home to celebrate Christmas with your family as you had hoped, you will be spending the next decade or two -- your twenties and thirties -- in a prison cell in a foreign country. When your deceased friend's relatives are watching with satisfaction as you are led, sobbing and wailing with desperation, to a van which will transport you back to that cell. (Ever thought about what that ride must be like?) 

While we're busy eliminating hunger, disease, and death itself, I hope we can also find the time, somewhere along the way, to get rid of that, too.

(The Associated Press reported that, apparently, Amanda had some trouble going to sleep after the midnight verdict.) 

I'll conclude with this: the noted mathematician Serge Lang was in the habit of giving his students "Huntington tests" -- named in reference to his controversy with political scientist Samuel Huntington, whose entrance into the U.S. National Academy of Sciences Lang waged a successful campaign to block on the grounds of Huntington's insufficient scientific rigor.

The purpose of the Huntington test, in Lang's words, was to see if the students could "tell a fact from a hole in the ground".

I'm thinking of adopting a similar practice, and calling my version the Amanda Knox Test. 

Postscript: If you agree with me, and are also the sort of person who enjoys purchasing warm fuzzies separately from your utilons, you might consider donating to Amanda's defense fund, to help out her financially devastated family. Of course, if you browse the site, you may feel your (prior) estimate of her guilt taking some hits; personally, that's okay with me.

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Komponisto makes a strange assertion. The prior is not the reference that "someone would commit murder" - there is a body. A more appropriate prior is "someone who lives with someone who was murdered committed that murder" - I'm guessing that base probability is of the order of 0.1. Once we take into account that AK and MK aren't in a relationship, AK is female, and there is very strong evidence that someone else committed the murder then I'd agree that the probability drops, but these pieces of evidence don't cancel out leaving us with the original prior - the final probability may be higher or lower.

Also the "complexity penalty on the prosecution's theory of the crime is enormous" - that may mean the case was flawed, but it's not evidence she didn't kill MK unless you are willing to give some weight to the conviction (at <0.001, I assume you are not). Or to put it another way, even if the prosecution is completely wrong you cannot set the probability of guilt to 0. This is like assuming AK is guilty because her parents criticized the Italian legal system.

Overall I hope I am a bit more cautious about my abilities than you. In the first half you explain why you, as a human being, cannot be trusted to be rational. Then you set out your case. Why should I trust your rationality, but not others'?

I think this is a good point, but I would go one step further. Because there was more than one crime committed. In addition to a murder, somebody tried to stage a burglary. Common sense says that whoever staged the burglary was also involved in the murder but it's still 2 separate crimes. It seems to me that the prior probability that the person who staged the burglary is someone closely associated with Kercher, such as a roommate, is actually pretty high. A close associate would have a strong incentive to try to make the police think that a stranger committed the crime. Whereas a stranger or remote acquaintance would have little or no incentive to do so.

Or at least injustice has stopped being served.

Overturned, though. With regards to "bayesian" analysis in question, as dilaudid said, the fact that a body was found makes for a fairly high probability that one out of a fairly small number of people connected to the victim has committed or participated in the murder. Even more so for a staged break-in. The reason why we shouldn't imprison people based on things such as apparently weird behaviour has little to do with it's impact on probability, and everything to do with the potential for the abuses that a subjective criterion would create, as well as discrimination against "weird people" such as borderline autistic. We have to think what is going to happen on the bigger scale if we start using "weirdness" as evidence in the court. The issue in this case is that the narrative presented by the police seems incredibly improbable even given all the facts, and there are far more probable narratives where she committed a lesser crime (such as being an accessory after the act). People who would commit murder are much rarer than people who may act as an accessory.
That took a while. BTW, it just struck me, why do we tend to talk about Amanda Knox and fail to mention Rafaelle Sollecito?

Amanda Knox is American, so she gets more attention from American news media.

And a white female. Don't forget that part.
And easier to type out.
Mostly because she is more attractive.
Thanks for the link; I've updated both predictions on

"But come on," says a voice in your head. "Does this really sound like the behavior of an innocent person?"

Absolutely. I saw the amount of emphasis prosecutors (and 'guilty' advocates) were placing on this sort of crap and immediately updated in favour of innocent. Presenting lots of ridiculous nonsense is evidence that you haven't not anything better.

"But come on," says a voice in your head. "Does this really sound like the behavior of an innocent person?"

Absolutely. I saw the amount of emphasis prosecutors (and 'guilty' advocates) were placing on this sort of crap and immediately updated in favour of innocent. Presenting lots of ridiculous nonsense is evidence that you haven't not anything better.

What I found most interesting about this exercise is the number of people who made this deduction. It is an error. They are appealing to the public and the jury, whose rationality you impugn. The prosecutors and especially advocacy websites will present (a lot of) this crap regardless of whether they have better evidence. This is normal behavior for prosecutors, just as changing stories, implicating random people, and signing confessions is normal behavior for innocent people. Similarly, differences in tone and organization of the two advocacy sites is pretty much useless.

Douglas, you mention that crap evidence is "normal" even if they have better evidence, but is it normal to not also present the claimed better evidence?
I am not convinced. The ratio of speaking nonsense to providing relevant evidence is a valid signal even with our less than entirely rational species.

Measuring cellphone call times down to "3 seconds" is meaningless. Mobile-to-mobile call setup times over the cellular network can easily be 4-5 seconds or more. While the network is trying to find the phone you called guess what ... you hear ringing on your phone even though a connection hasn't been set up. So it wouldn't be unusual for the caller to hear 5-6 seconds of ringing before the called phone starts ringing. 3 seconds of ringing on the called phone could easily translate into 6-9 seconds of ringing on the calling phone.

In the US, I prefer to hang up before the voice mail prompt. It leaves a missed call message and makes it easier for the called party. But when in Italy, better let the phone ring until voice mail just in case the called party died ....

Here's a thought exercise, that for me clears the confusion in this case. Pretend that you don't already know who the suspects are in this case, and are looking at the evidence to try and find one for the first time. You have no preconceived notion as to who killed Kercher.

Your evidence comes in two weeks after the killing and you have a bloody hand print on a pillow, fingerprints elsewhere in the room, saliva DNA outside the victim and skin or saliva DNA inside the victim as well. All of this is of one person, Rudy Guede.

You look up Rudy Guede and you find that in the weeks prior to the murder he was involved in three separate break-ins involving a knife, but was not arrested. When you try to locate him, you find he has fled the country to Germany.

At this point, do Knox and Sollecito even come into this story as anything other than footnotes? There are no interrogations, no cartwheels, no rumors of bleach purchases, no "foxy knoxy", no stories of sex on a train, none of it. The knife in Sollecito's flat, with a minuscule amount of DNA on the blade that doesn't identify Kercher but can't exclude it never enters the scene. Neither does the bra clasp found 47 days later.

Blood drops of the victim found in a co-habituated bathroom with mixed DNA of roommates doesn't seem all that sinister.

For me, this clears up who the guilty party in this case quite nicely, and takes my "feelings" out of the equation.

In fairness, aren't you also starting with some or all of the following pieces of evidence?: (1) A room in the crime scene apartment has been ransacked but no valuables (which were in plain view) were taken; (2) A window in that same room has been broken with marks suggesting it was broken from the inside; (3) the same window is on the second floor and can be seen from the street. Further, there is no obvious reason why a burglar would need to get in through an upper floor; (4) Bloodstains indicate that the victim died with her bra on and the bra was removed a few hours later; and (5) When the police arrived at the crime scene apartment, one of the victim's flatmates was standing there with her boyfriend and with a mop and a bucket.
1) Actually, Kercher's rent money was missing and Guede's DNA was found in her purse. After her murder he went clubbing and then hopped a train Milan. Where did he get the money to do that? To state there was no robbery doesn't jibe with the evidence. Knox had $2000 in her bank account, and Sollecito's parents are well off. Guede was a known drifter known for his money problems. 2) No, evidence was NOT that window was broke from the inside. The glass was inside the room, and a rock was found. The dispute arises because some glass was below clothing in Filomena's room. However, Filomena was allowed into her room to retrieve personal effects, so the exact placement of clothing is suspect. Furthermore, the building itself is fairly isolated and traffic along the road is minimal. 3) There is a truss next to the window making access relatively easy. An investigator for the defense, dressed in a suite and tie easily scaled it. Rude Guede was an accomplished athlete and basketball player. 4) That's an evaluation of the judge who accepted the prosecutor's contention of the muti person scenario. Scientific testimony at trial contradicts this assertion. In either case, this is evidence open to interpretation. Even if that were true, there is still no evidence that Knox or Sollecito were involved in moving the body! Putting them in the room a SECOND time hours later further creates a logic problem because no evidence of their presence is in the room! What are they, ghosts?? Even if you prove there was more then one assailant, you still have to prove those additional assailants were Knox and Sollecito... which you can't You must UNLEARN what you have learned my friend. ;) 5) No such evidence was presented at trial, and even if it was so, its completely meaningless. How do you get from "a mop and bucket" to "a three way sex crime"? You must have something stronger in addition to the observation for it to have probative value of a crime! If they cleaned the crime scene how di
Hold on a sec: Are we looking at things from the perspective of the initial evidence available to investigators? Or are we looking at all the evidence in its totality? These are two separate but related questions: (1) Does the initial evidence offer a reasonable basis to be suspicious of Knox and/or Sollecito? (2) Does all the evidence in its totality indicate that Knox and Sollecito are guilty? It seems to me you just jumped from discussing (1) to discussing (2). If you want to do that, fine, but in that case it's not fair for you to ignore later evidence which developed against Knox and Sollecito. I'm not doing that at all. The mop and bucket are one initial piece of evidence which, when combined with other initial pieces of evidence, form a reasonable basis to be suspicious of Knox and Sollecito.
How is the mop and bucket evidence of a crime??? That's an emotional response, not a rational one. You must prove 1) the mop and bucket was used to clean up a crime scene, and 2) that Knox and Sollecito were the one that did it. No proof of 1 exists, so how can you prove 2? 1) I'm saying that if you follow the evidence, Knox and Sollecito never enter the picture as suspects. I do not assign behavior as evidence of a crime without strong physical evidence to cooberate it. All we have initially are the behaviors. 2) The evidence in totality can't connect them to the crime or Guede. Guede is completely connected by the evidence. So how can you prove guilt? I'm saying this: If you START with the cold hard evidence, and proceed from there, Knox and Sollecito are NOT suspects. Since they are not suspect, their behavior isn't probative, and everything that follows: "Foxy Knoxy", Vibrators in the bathroom, sex on a train, cartwheels at the police station have 0 value as evidence of a crime. Get it? I'm time warping. Starting with the evidence to find the people, not starting with the people and then trying to find evidence to implicate them. Its a thought exorcise.
It's evidence that Knox and Sollecito had been cleaning something up, either because they were trying to conceal evidence of a crime or because they were just doing ordinary cleaning. It would have been a bit of a coincidence for them to have been doing ordinary cleaning on the same day that (1) Knox's roommate was murdered; and (2) Knox suspected that somebody had burglarized her apartment. Not an outrageous coincidence but it does raise the suspiscion level a little. So you are saying that INITIALLY, there was no evidence of staging/alteration of the crime scene?
I'm saying that Kercher had $200 in cash and it was missing. Guede's DNA was in her purse, and he needed money to flee the country. Thus, there is strong evidence of a robbery. Saying nothing was taken is simply ignoring the facts. Interpretation of staging is exactly that... interpretation. If you say it was staged, that helps support the prosecution's version of the crime, but it does not support the totality of the physical evidence. You can infer whatever you wish from the mop and bucket, but without substantiating evidence it means nothing.
Respectfully, does that mean "yes" or "no"? P.S. By "initially" I mean just looking at the crime scene evidence.
Respectfully, it doesn't matter. You're missing the whole point... and I'm not trying to be flip. I apologize if it appears that way. Let's play devil's advocate and say there was unequivocal proof of staging/ alteration of the crime scene occurred. You must now prove that Knox or Sollecito were the ones that did it. Your suspicion that they did it is not evidence.I understand about "initially", but in order to conduct the investigation you must start with the obvious and work from there. I find it very difficult to START my investigation with Knox as a suspect based on what was found initially. The further away you move from the point of origin of the event, the less accurate your observations will be.
Ok, fine. I'm a little confused. I thought your point was that the initial physical evidence offered no reason to suspect Knox or Sollecito and therefore subsequent evidence developed against them should be discounted or even disregarded. In that case, the question is not whether the evidence proves Knox is guilty but whether it provides a reasonable basis to suspect her. Did I misunderstand you?
Here's exactly how Knox arrived on the radar as a suspect. You tell me if this sounds right: "...Edgardo Giobbi, a police forensic scientist, told the court in Perugia how during a search at the house just hours after the murder, he handed Knox a pair of shoe covers to prevent contaminating the evidence. "As she put them on she swiveled her hips, pulled a face and said 'hop la' - I thought it was very unusual behavior and my suspicions against her were raised," Mr. Giobbi told the court..." My reaction to this statement was something along the lines of, "WTF?" It is natural in ANY investigation to first look at the people who live at the house, but you can't let that give you tunnel vision to the physical evidence around you.
What about the knife wounds? Were the wounds consistent with different knives or not? If they were, and if it is true that the bathmat print was Raff's, and other prints were wiped off the floor, then: Is it theoretically possible that Raff walked into the room and stabbed a dying woman? - that would not lead to leaving DNA only on the floor and the knife - which may have been a different knife, from the one in the flat, and was discarded and never found? Surely, if the jury convicted on the basis of the prosecution's story then they must have gone into detail like that in order to examine the plausability of the reasoning? With all the uncertainty about the many disparate bits of evidence and/or red herrings, I don't see how one can judge the judgement without reading the whole proceedings. Certainly I agree that there is no real evidence that Raff and Knox were tumbling around the room with Meredith. But I think what is on trial is how murders come about as much as the act itself. That may be a difference in Italian law. I think some people feel that Knox and Raff may have been morally responsible, by their inconsiderate behaviour. Maybe they were bullying Meredith a bit and playing games that maybe Guede didn't understand.
By the way, as a point of information, do you have a cite for that? TIA. (Of course my main question is whether I have understood you correctly. Are you saying that the initial physical evidence offered no reason to suspect Knox or Sollecito and therefore subsequent evidence developed against them should be discounted or even disregarded?)
I agree, but so what? The issue of whether the police developed tunnel vision is a different question. Anyway, please tell me if I misunderstood you. Your point seems to be that the initial physical evidence offered no reason to suspect Knox or Sollecito and therefore subsequent evidence developed against them should be discounted or even disregarded. Did I get you right? Or did I misunderstand?
The problem is there is no "subsequent evidence!!" Behavior is not evidence. You must prove that the accused were involved in a crime. Otherwise, lets burn witches. Footprints in blood? No. Luminol reveal no blood, so footprints in the hallway of a person who lived there means nothing. Likewise, Knox's DNA mixed in droplets of Kercher's blood in the bathroom that they shared is hardly startling. DNA of people who cohabitate mixes all the time whether or not a crime is committed. There are only TWO pieces of evidence that are said to connect Sollecito and Knox to this crime. The knife and the Bra clasp. An independent report done by the innocence project who directly examined the tester's reports clearly show this "evidence" is hardly proof of anything. Some wonderful links, that include actual crime scene video shot by investigators and the DNA report compiled by the Innocence Project: And a link that was requested by Braz:,2933,523400,00.html
"The problem is there is no "subsequent evidence!!"" Of course there is subsequent evidence. For example the fact that Knox and Sollecito were unable to coherently, consistently, and reasonably account for their activities and whereabouts during the time period in question. That's evidence. And by the way, by "evidence," I don't necessarily mean the same thing as "proof"
Ah, but you are under the FALSE assumption that their stories should match or even be cohesive! Investigators will tell you that people's recollections of same events, especially when they are under pressure often vary widely. Eyewitness evidence is the most unreliable type. Thus, if their stories matched, that may indicate a rehearsal before hand. If they had been involved in the killing do you not think they would have tried to get their story straight? They had 5 days to talk about it. Thus, in reality, this points more to a lack of guilt that an indicator of it. Here's a fun read: Anyone with a cursory knowledge of police interrogation techniques knows its just one big "gotcha" game. Confusing the suspect, and undermining their understanding of their reality is basic to "breaking" a suspect. It's a shame that we don't have a video of the interrogation (as required by Italian law). So we only have the police version of events to go by as to what transpired. As you might guess, that doesn't inspire me with a lot of confidence as to the veracity of their statements. And, hey, while we're on the subject of changing stories: the initial theory of the crime was a ritualistic rite to celebrate halloween, then it was a sex game gone bad, then it was an argument over Meredith's missing rent money, then it was revenge on the "smug," "prissy" girl, then it was "sometimes there is no reason. Mignini changed his story more times than Amanda and Raffaele put together, but that doesn't seem to bother a lot of people. It really bothers me.
You are shifting arguments yet again here. Anyway, there is a distinction between the sorts of inconsistencies which result from typical human error and the sorts of evolution, tailoring, incoherency, convenient amnesia, etc. which result from prevarication. Knox and Sollecito's stories pretty clearly fall into the latter category.
My arguments have remained consistent. You are the one that keeps inserting interpretative observations into this discussion rather than sticking with the objective level facts.
Your argument keeps changing. First you argued that there was no physical crime scene evidence which would cause one to suspect Knox or Sollecito. Then, when that turned out to be untrue, you argued that the police acted unprofessionally. Then, when I pointed out that was irrelevant you claimed that there was no subsequent evidence against Knox or Sollecito. Then, when I pointed out subsequent evidence you tried to explain it away. Now you simply accuse me of "inserting interpretive observations" into the discussion. I'm not sure what that means. Maybe it's like the "leap" distinction which other posters tried to draw earlier. Can you give me two examples of the "interpretive observations" I have been inserting into the discussion?
Is it ok if I give you six? interpretive observations: (1) A room in the crime scene apartment has been ransacked but no valuables (which were in plain view) were taken; (2) A window in that same room has been broken with marks suggesting it was broken from the inside; (3) the same window is on the second floor and can be seen from the street. Further, there is no obvious reason why a burglar would need to get in through an upper floor; (4) Bloodstains indicate that the victim died with her bra on and the bra was removed a few hours later; and * (This was the opinion of a judge. A Forensic scientist for the defense later refuted this contention.) (5) When the police arrived at the crime scene apartment, one of the victim's flatmates was standing there with her boyfriend and with a mop and a bucket. (6) inconsistent stories. At the end of each of these ask yourself this... how does this connect Knox or Sollecito to the crime? Objective level facts: * Guede's DNA inside kercher * Guede's Bloody fingerprints (with Meredith's blood) on kersher's pillow case * Guede's feces in the toilet * Guede's DNA in Kercher's purse Ask yourself this. How does this connect Guede to the crime? See the difference? I sell cars for a living. My BS detector is off the scale. ;) The opinion of this case by another attorney (just for fun):
It sounds to me like you are claiming that the case against Knox and Sollecito is based mainly on circumstantial evidence. Is that about right?
Exactly, and were Knox and Sollecito the only two people charged in this case you MIGHT have a case (a very poor one). However, to compound the problem even more, you have another suspect for whom the evidence is overwhelming. The evidence against Guede is so geometrically out of proportion than that against Knox and Sollecito that it defies logic. How can that be, if these three people participated in this crime? The only logical answer is very simply... it can't.
It's still possible to reach reasonable conclusions based solely on circumstantial evidence. For example, I am reasonably confident that OJ Simpson killed his ex-wife based solely on the facts that (1) he is her ex-husband; (2) there is a violent history between them; and (3) he cannot account for his whereabouts around the time of the murder. Of course here, Knox and Sollecito had no obvious motive to kill Kercher, but the same principle applies, i.e. it's possible to be reasonably confident in a conclusion based solely on circumstantial evidence. Many ways. For example, it is possible that Knox and Sollecito hired Guedo to kill Kircher but did not participate in the actual stabbing. (I'm not saying that this is what happened, I'm just pointing out that it is possible that Knox and Sollecito were involved in the murder even though there was (apparently) none of their DNA on Kercher's body.)
I'm sorry Brazl, but now you're just reaching and I'm going to have to call you out on it. No offense. For your argument to have weight it must be based in facts. My original argument was that had the investigators followed the facts, Knox and Sollecito would not have been (let me add the word "viable" here for clarification) suspects. Your arguments have done nothing to undermine that assertion. If anything, they've only strengthened them, for you have yet to name ONE objective level fact to tie them to the crime. Even in a circumstantial case, you still need facts to support it.
Sure, and the facts suggested a staging/alteration. The killer (or a killer) would have had a strong motive to do so, as well as the best opportunity and means, if he or she was a flatmate of the victim. That's plenty of evidence to make Knox (and by extension Sollecito) a viable suspect. See above.
Sorry Braz, but that's still Interpretative Observation. The staging/ alteration itself is open to interpretation 1) at trial the defense presented a very viable argument as to why the scene was NOT staged (Filomena had unsupervised access to her room to retrieve some personal items and may have moved things. There's more to it, but I can't specifically remember and I'm too tired to go hunting for links.). and 2) You still must somehow connect Knox and Sollecito to the staging (if such staging actually occurred... which you can't conclusively prove either). Objective level facts of Guede: I can conclusively prove that Guede had sexual contact on the night of the murder, he was there, and Kercher bled extensively in his presence. Good night Braz.
I'm a little confused. Are you saying that nobody can ever become a viable suspect on the basis of circumstantial evidence alone? Are we talking about conclusive proof or reasonable suspicion? I'm happy to discuss either one, but please choose one or the other.
I apologize, you are correct... I was inferring reasonable suspicion. Conclusively implies 100% certainty and that's hardly ever possible in any case. I can say that I am 95% sure, Knox and Sollecito had nothing to do with this crime base on the evidence presented. I can say I am 95% sure that Guede Killed Meredith Kercher. To get an idea of how warped this investigation has been, let's look at a statement from trial judge Judge Paolo Micheli who discounted the "lone wolf" theory and how he arrived at his conclusion: “I took the opposite approach to that of the defence teams. The lawyers claimed that there was no proof of conspiracy between the three because they didn’t know each other and Kokomani’s testimony wasn’t reliable. They also said that it would have been impossible for them to have organised the crime since they had previous commitments which then fell through. My starting point was the three’s presence in the room where the crime was committed” i.e. Let's just forget about doubts that Knox and Sollecito knew Guede and were involved in a conspiracy, and just assume that's true. WTF? Innocent until PROVEN guilty is suppose to be part of the Italian justice system, yes? Begin with a flawed premise, you come to a flawed conclusion. The judge further states that he discounts the contamination of the bra clasp because Sollecito had no reason to go into that room. Well, what about the three unknown people's DNA on the bra clasp? Who are they?? They are not anyone connected to anyone with the flat as it was compared to all the tenants and their boyfriends. A lab tech's maybe? Knox and Sollecito are simply not viable suspects in this crime... at ANY point, and the evidence has been blatantly "shoe horned" to make them fit from the beginning. Under close scrutiny and logical thinking it just doesn't make sense... from the beginning days of the investigation, to the closing arguments of the prosecutor who couldn't settle on a theory of the crime.
I'm still confused. Please just answer my question: Are you saying that nobody can ever become a viable suspect on the basis of circumstantial evidence alone? Also, do you agree that the killer (or a killer) would have had a strong motive to do engage in staging/alteration, as well as the best opportunity and means, if he or she were a flatmate of the victim? Please just answer my questions. It's just two simple yes or no questions.
No, I'm not saying that at all! You are assuming that the assertion of staging is true and there are no alternate explanations... so no. Here is a neat little compilation I found prepared by "Friend of Amanda" that summarizes the important points nicely. It's easy reading and worth a look
Then I have no idea what your point is. You seemed to be arguing that Knox and Sollecito were not viable suspects because (initial?) evidence against them was circumstantial. And yet you admit that circumstantial evidence can indeed form a reasonable basis to make somebody a viable suspect. No I am not. Again, there is a distinction between between evidence and proof.
Braz, WHAT initial evidence against them???
For one thing, the fact that blood stains indicated that the victim had her bra removed some hours after she was initially attacked. For another, the fact that a room in the flat was ransacked but nothing was taken even though valuables were in plain view. Just because this is circumstantial evidence doesn't mean it's not evidence. Just because this evidence does not prove Knox's guilt doesn't mean it's not evidence. Just because there are ways to explain away this evidence doesn't mean it's not evidence. So please don't respond by arguing either (1) this evidence can be explained away; or (2) that it's circumstantial; or (3) that it doesn't prove Knox's involvement.
You didn't establish that these are evidence against Knox and Sollecito. To do so, you must explain why these facts elevate the probability that Knox and Sollecito in particular were involved in the murder.
Actually I did in a previous post. As noted in that post, someone involved in the murder would have had a strong motive and the best means and opportunity to engage in staging/alteration if he was a flatmate of the victim. Someone with little or no connection to the victim would not have had much incentive to engage in staging/alteration. And someone who did not live in the flat would have had far less confidence in returning to the crime scene or staying at the crime scene for an extended period of time. Why? Because such a person would naturally worry that another resident of the flat would already be there when he or she returned. Or would return while her or she was there. So if the crime scene really was altered/staged, the natural suspect is a resident of the flat (and anyone acting in concert with him or her).
Okay. I agree that evidence of very time-consuming alterations is evidence that the alterer didn't fear interruption. Now, what was the evidence that the bra was removed "some hours" after the murder? More pertinent to the point: Was the delayed removal of the bra noticed before Knox and Sollecito were suspects? That is, was it initial evidence, as captcorajus requested? As for the ransacking, I expect a fake ransacker to be about as likely to fake-steal things as a real ransacker would be to really steal things. Therefore, the failure of the ransacker to steal is not much evidence either way regarding the genuineness of the ransacking.
It's on the anti-Knox web site linked to from the "you be the jury" post. If you really want, I will try to dig up a link for it. I don't know, but in most of my posts I've been using the word "initial" to mean evidence which could be developed from the crime scene without having any particular suspect in mind. "initial" in a logical sense rather than a chronological sense. If you read back through captcorajus' comments, you will see why that makes sense. But I do agree it's a sloppy use of the word "initial" I suppose it would be better to call it "a priori" evidence. I wouldn't. For one thing, if you fake-steal things, you have to take time and energy to dispose of them somewhere and you have to worry that your fingerprints or DNA will be on them. For another, if you have just killed someone and you have never given a lot of thought to staging a crime, there's a good chance it wouldn't occur to you that you actually need to fake-steal stuff to make it look good.
I was able to find claims that the bra was removed and the body moved "some time" after her death, but not "some hours". Any murderer would have been with the body for some time after the death. [ETA: I also couldn't find what evidence established that the bra had been removed even "some time" after death.] But, if the murderer stayed for multiple hours, I would consider that to be evidence that the murderer had some confidence that he wouldn't get caught by the residents. Then, I concede, it becomes necessary to consider how likely different people were to have had that confidence.
You may be right about "some time" versus "some hours." However, there was also the claim that the victim took quite a while (an hour?) to actually die from her wounds. So it does not seem the murderer would need to have been with the body for some time after the death. The actual evidence, as I recall, was (1) that there was in impression in the dried pool of blood under the victim from her bra; and (2) there were minimal blood stains on the victim's breasts compared to other parts of her upper body.
I would expect any murderer to stay long enough to ensure that the victim was dead. If the victim was alive during the "some time" needed to remove her bra, then that event doesn't add significant probability to the guilt of Knox and Sollecito. Any murderer would want to make sure that the victim didn't live long enough to identify him.
I wouldn't necessarily expect that. The murderer might very well just panic and run while the victim lay dying. Indeed, one witness apparently reported hearing a scream followed shortly by running footsteps. In any event, I would guess that the normal way to make sure somebody is dead is to keep stabbing them until they stop moving. Apparently the victim in this case stopped moving for a while ("quite some time" was the phrased used on the anti-Knox site) before she was moved and her bra cut off. It's hard for me to believe that a random killer would watch the victim die; watch her motionless for a long enough for her blood to dry significantly, and only then move her and cut off her bra. All the while wondering if somebone else is about to enter the apartment and discover him.
In order for you to believe that the bra must have been removed more than minutes after the stabbings, you must believe one of: 1) the bra was removed in a way that rubbed the material all around her breasts, not cut or unclasped and lifted straight off. or 2) blood was still dripping significantly from a wound or large smear uphill of the breasts relative to the body's orientation Evidence I'd accept for 1: smudging suggestive of sloppy bra removal, but with less blood smear than you'd expect from unclotted/dried blood. But I'd need a wide range of lab experiments producing similar marks by smearing different-aged blood in order to know the timeframe. Evidence I'd accept for 2: pattern of blood flows around the breast may suggest one or more orientations of the body before total drying. But even if the bra was removed hours later: who says K/S did it, and who says that raises the likelihood of their also stabbing the victim above 1%? I would be interested in what the killer was doing hanging around for hours, if it turns out he did, but that's not impossible either.
In terms of probabilities, if the crime scene was altered, there's a pretty good chance it was done by someone who lived in the apartment. Why? Because a resident of the apartment would have an incentive to do so and would have a much better opportunity. To me, the question is not whether Knox stabbed the victim so much as whether Knox was involved in the murder.
If I own or rent a residence, and one of the residents is killed there, I agree that I expect some suspicion to fall on me. I don't agree that I'm therefore very likely to attempt to cover up the crime. In fact, it would be irrational, unless I think the authorities are extremely likely to railroad me out of laziness. I'd say, if the crime scene was covered up in any way, I'd suspect the perpetrator first. I read a little more about the case; apparently it was mostly throat-slashing. On the whole, I think it's crazy to suspect that Knox did the slashing, ultimately mostly on the basis of "her behavior was strange" (under extreme duress).
There's a difference between (1) the probability that a resident will attempt to alter or stage the crime scene; and (2) the probability, given that the crime scene was altered or staged, a resident is responsible. Respectfully, I don't think that's a fair summary of the evidence against Knox.
True. There's some physical evidence that can be interpreted as implicating her. I just meant that her prosecution was ultimately caused by a feeling of "her behavior is strange".
There was a side-discussion in another thread about how it is quite likely Amanda Knox is a sociopath and that could have made the prosecution think she was guilty and explains some of her strange behavior. But, sociopaths are 5-10% of the population and being a sociopath only marginally increases the probability of committing murder.
If you are saying that the police became suspicious of her at the very beginning because her behavior seemed strange, then you may be right. How should this affect our assessment of the probility she is guilty? I would say it depends on exactly what strange behavior you are talking about.
Whether to suspect her or not isn't the issue. By virtue of her being the victim's roommate, the police should look at her. That's CSI 101. However, announcing that the case is closed, and that the murder was the result of a ritual sex game gone wrong before you've looked at the forensic evidence seem not only premature, but unprofessional. How can you even come up with such a theory on your interpretation of behavior alone? That says more about the observer than the observed, eh? For example, much has been made about the "cartwheels" in the police station. Were you aware that Knox was a dancer and practiced yoga? Where you aware that she frequently used yoga positions to relieve stress? Where you aware on the night this was observed she had gone to the station with Sollecito who had himself been summoned by the police? She went voluntarily to the police station. That's not the behavior of a guilty person. No one that knew her was surprised that while she was waiting she would do yoga stretches to relieve tension. Yet the police took this behavior as odd, and that she wasn't properly grieving for her roommate, yet for Knox, this was normal. This is what I'm talking about... making premature assumptions with little corroborative evidence invariably heightens the odds of coming to the wrong conclusion. I'm saying that the evidence they had on hand at the time does not add up to the conclusion they reached.
That's different from what you seemed to have been saying before. Your position now seems to be that the police acted unprofessionally and focused on Knox without a reasonable basis. You are saying that they concluded Knox was guilty without a sufficient basis. First of all, I am skeptical of your claim. I asked you to provide a cite for your claim about the source of initial suspicion of Knox and you failed to do so. I did my own search and found nothing backing up your claim. But more importantly, your argument doesn't have much bearing on the ultimate question of guilt or innocence of Knox or Sollecito. If I were arguing that Knox and Sollecito are probably guilty because the authorities concluded they were guilty, then you might have a point, assuming you could substantiate your claims. In that respect, it's a bit like the OJ Simpson case -- the police may very well have rushed to judgment against OJ. But even so, it seems very likely that he committed the crime he was accused of.
brazil84, I just don't think you have a grasp on how weak the case against Knox and Sollecito is. You've said that the two things that make you think they did it -- the changing stories and evidence of crime-scene-tampering -- contribute 3 or 4 bits of evidence against them. That's quite a small amount, which is easily overwhelmed by : * The prior improbability that people like K and S would be involved given that someone else was. * The lack of criminal history of K and S. * The lack of motive. * The lack of connection between K/S and G * The lack of any evidence that K and S themselves were at the scene. I understand that you feel suspicious of Knox and Sollecito based on the reports you've read (the prosecution's narrative does sound like a good made-for-TV-movie), and have a great deal of faith in courts due to your background as a lawyer. In most trials, the defendants are probably guilty. But this isn't a typical case. There are times when you have to look at the object-level facts, and, frankly, do the math. Sometimes, police, prosecutors, and juries are just plain wrong -- stupidly so. This is one of those times.
Actually, the 3 or 4 bits was based on the assumption that there was no a priori reason to suspect Knox or Sollecito, such as an obvious motive. Putting aside the issue of my faith in the courts, I have a decent amount of faith in my ability as an attorney to detect BS. Believe it or not, I have people calling me day in and day out, lying to me and trying to convince me to take their case. For the past few years, I have worked mainly on contingency, so if a prospective client succesfully snows me it's a complete waste of my time and money. As a result, I've gotten pretty good at assessing cases based on limited evidence. I'm analagous to a professional oddsmaker and most of the folks in this thread are analogous to amateurs telling me I've got my odds wrong. Which is of course possible. It happens all the time that the so-called experts are caught up by amateurs. Still, while I've never been involved in a murder case, I have heard literally hundreds of stories of people who have denied wrongdoing, evaluated their cases, and then had the opportunity to learn more through discovery and trial. In this case, it's pretty clear to me that Knox and Sollecito are hiding something important. I've interviewed and cross-examined dozens if not hundreds of witnesses whose stories evolved in a similar fashion to meet evidence against them, often ultimately turning into "I don't remembers" when faced with important contradictions. When further evidence is available, it almost always goes against the stories offered by such folks. 7 or 10 years ago, I would have been a lot less confident that Knox and Sollecito were involved in the murder. But after the experience of having seen hundreds of people lie and attempt to cover up their misconduct, I'm pretty confident that they were involved.
I'm beginning to wonder what evidence could possibly ever convince you that a defendant was innocent. DNA incriminating someone else? We've got it here -- the DNA shows it was Guede. Prosecutorial irrationality and misconduct? Cornucopias full of it: they came up with their theory before knowing about Guede, and didn't drop it once he'd been caught; furthermore, Mignini is under indictment for misbehavior in another case, and is notorious for bizarre conspiracy theories. Et cetera. All those people exonerated via the Innocence Project? Well, there must have been something suspicious about them, or they wouldn't have been prosecuted and convicted. Why should we be so quick to jump to the conclusion that they weren't involved, just because the DNA points to someone else? (The irony here is that, were it not for the fact that Guede has already been nabbed, this case would itself be a perfect candidate for the Innocence Project. Given what was used to convict Knox and Sollecito, we may as well still not know about Guede. In which case, the DNA tests showing that it was someone other than Knox or Sollecito would be considered exculpatory, rather than indicative of a three-way conspiracy.) Write it out. Write out the evidentiary value of each piece of incriminating evidence, together with the values of the various pieces of exculpatory evidence I listed, and do the addition. Make your assumptions transparent for all to see. "My lawyer's intuition tells me" isn't an argument. Beliefs have to be based on evidence. Until you can unpack your intuition and show specifically how the evidence leads to your belief, you might as well be saying you looked into a crystal ball.
I'm satisfied that the defendants in the Duke lacrosse case were innocent. And I was reasonably confident of that long before the state prosecutor announced his belief they were innocent. You are attacking a strawman here. I have refrained arguing that Knox and Sollecito are probably guilty simply because they were charged and ultimately convicted. I will if I can find a block of free time in which I have the motivation to do so. Again you are strawmanning me. I am saying that as an attorney, I have heard hundreds of people give statements or testify. In situations where (1) peoples' stories have been incoherent/inconsistent in a manner similar to that of Knox; and (2) further evidence became available, that further evidence has virtually always gone against the person's story. Sometimes dramatically so.
I didn't say that's what you argued. I said that if you were to look into the cases of those defendants later considered to be exonerated by DNA evidence, you would likely find grounds for being suspicious of them similar to the grounds on which you are suspicious of Knox and Sollecito. (In fact, I am given to understand that 25% of them actually confessed to the crime.) Meaning that they were browbeaten by police into speculating on how their understanding of the situation might have been wrong? I'm honestly not sure what you're talking about here. One keeps hearing these claims that Knox was "inconsistent", "changed her story", and the like. But the account given at Friends of Amanda seems perfectly convincing to me. From the beginning, Knox insisted she was at Sollecito's. But she was told (falsely) that there was solid physical evidence placing her at the crime scene. This was understandably confusing to her. So after hours of being berated by interrogators, she finally gave in to their pressure by speculating -- upon their prompting! -- about Patrick Lumumba. This doesn't sound like evidence of guilt to me. You say that it does to you because of your experience as an attorney, but you're going to have to do a better job of explaining why -- and more importantly, why it comes anywhere near to trumping the other evidence.
At a minimum, you responded to the argument as if somebody had made it. Since you were responding to my post, it's reasonable to infer that you were attributing that argument to me. No. During what time period? From approximately what hour to approximately what hour?
This is stupid. The reason the further evidence turns out to go against them is because they're guilty, not because their stories were incoherent. Don't you think that the vast majority of criminal cases coming to your attention are, by the prosecutor's discretion and incentive, ones where a strong case for the defendant's guilt can be made? That's all the explanation you should need of the phenomena you recount.
No, that's not it. Their stories are incoherent because they are guilty AND the further evidence goes against them because they are guilty. No -- I don't practice criminal law. I practice civil (administrative) law. Perhaps 40-60% of my clients are innocent of the charges against them and I win more than half the time.
I don't think you're allowing much possibility for an innocent who has a suspicious story. You think p(guilty|incoherent) is higher than p(guilty|coherent). I agree. I'm saying that p(guilty|incoherent,criminal prosecution) is very close to the baseline p(guilty|criminal prosecution), because you only see prosecuted those cases where either the defendant is unlucky enough to have a sketchy-seeming alibi, or the direct evidence is strong enough that the alibi doesn't matter. Since your experience is from criminal cases, my speculation about it was inaccurate; on the other hand, that means that your experience is even less relevant than I thought. Many civil cases go to trial where, as you say, p(win) is nearly 1/2. Not so for criminal prosecutors; they drop cases they won't win.
I'd like to back away from my initial response ("this is stupid") to you. I had understood you to be talking about personally observed frequency of (incoherent and guilty) vs. (coherent and not guilty) in the context of criminal testimony in court. Clearly that's not the case, and you had much more experience with innocent defendants than I anticipated. Also, I actually understood you to believe that the causation proceeded from incoherent -> guilty, which of course is ludicrous. You later explained that you actually have a roughly correct causal network; my only objection would be in whether you're using the proper frequency for (incoherent and innocent); only if it's nearly zero can you immediately conclude that incoherence very strongly suggests guilt. (otherwise, you have to do the math). I still hold that amongst criminal defendants at trial, (incoherent and innocent) may be quite frequent, because (coherent and innocent) are almost never brought to trial. But what's important is, amongst criminal defendants, how much higher p(guility|incoherent,trial) is than p(guilty|coherent,trial). I don't actually know precisely what the difference is; I also expect it to be higher, but dwarfed in importance by the additional evidence. I would be extremely hesitant to convict someone solely based on "suspicious cover-up like behavior", but I know that it's happened, e.g. in the case of Hans Reiser.
I also would be hesitant. And indeed, I don't know if there was enough evidence to inculpate Knox beyond a reasonable doubt. My point in these discussions is that I'm pretty confident she was involved in the murder.
I would say it's pretty relevant. I've questioned hundreds of people who were accused of wrongdoing; come to a belief about their guilt or innocence; and then had an opportunity to see further evidence against them and update my beliefs, so to speak. As to your point that there is a selection bias in criminal prosecutions, that may very well be the case. I'm not sure what it implies for the Amanda Knox case. I suppose one could argue that the decision to prosecute her is evidence of her guilt. Evidence in the logical sense, not the courtroom sense.
brazil84's points 1, 2, and 3 are false in my opinion, I have insufficient knowledge about #4 (the allegedly postmortem removed bra) but my reaction is "so what?" and "how does the investigator know the bra wasn't removed post-cut rather than postmortem?"), and here is my take on #5, the mop and bucket... The allegation that Amanda and Rafael were found with a mop and bucket outside the crime scene apartment is reported on (which has been accused of bias in some of the comments here.) claims to be paraphrasing a judge's statements about pretrial hearings. This alleged fact apparently did not come up in the actual trial. In the actual trial, Rafael's maid said she found a mop and bucket underneath the sink at his apartment, and said he explained that they had cleaned up some leaked water. The maid testified that there was a clear liquid in the bucket. My wild guess at the truth here is that indeed Amanda and/or Rafael had taken a mop and bucket from Amanda's apartment to Rafael's apartment to clean up a leak, and the maid saw it when she came in the morning (she cleaned around 11:00 on certain days, as I recall.) And then, possibly, and unfortunately for them, Amanda or Rafael brought the mop back to Amanda's apartment shortly before the police arrived. But your guess is as good as mine. One thing I stumbled across was this comment to a blog: I think that's pretty funny, or at least it would be if the freedom of two individuals weren't at stake. No evidence of bleach, by the way.
Well, do you agree that one of the residents of the flat stated that (1) she left her room without clothing strewn all over it; and (2) there were valuables in plain view which were not taken? Do you agree that a second floor window was broken? Do you agree that the same window was visible from the street? In short, I would like to know exactly where you disagree with the points I raised. And please don't simply offer explanations for these things based on the evidence in its totality. I raised these points to show that there was physical crime scene evidence which supports reasonable suspicion of Knox and Sollecito. Again, please keep in mind that I raised these points with respect to the issue of whether there were grounds to suspect Knox and Sollecito based on the crime scene evidence. If you would like to jump to a discussion of Knox's (and Sollecito's) guilt or innocence based on all the evidence in its totality, that's fine, but in that case we need to consider ALL the evidence, which includes evidence that was subsequently developed against Knox and Sollecito.
I agree that reported that one of the residents stated that she left her room without clothing strewn about and that she left valuables in plain sight that were not taken. I fail to see the relevance to Amanda, especially if the valuables were not clearly valuable or were easily traceable (e.g., the valuables could have been jewelry, which the murderer may have believed risky to fence or believed to be worthless costume jewelry.) Cash was taken. I agree that a second floor window was broken and that there was easy access to said window from the side/trellis. I fail to see the relevance to Amanda. You are implicitly referencing the glass-on-clothes argument. I am unmoved by this evidence that the window was broken from the inside because: 1. Glass fragments could wind up on top of clothes even if the window was broken from the outside. The clothes weren't strewn about before the incident, so, if the glass were broken from the outside then the clothes would have been strewn about after the glass fragments were on the floor, allowing fragments to roll up on top of clothes. 2. The murderer's objective after the crime seems to have been to delay discovery of the body. The murderer went into the bathroom outside the victim's room to clean himself, then went back into the victim's room, locked the door, and exited through the window. Therefore, even if the window was broken from the inside, which I really, really doubt, it makes sense from the murderer's perspective. Amanda and her boyfriend, on the other hand, sped the discovery of the body by calling the police (although, ironically, other police were already on their way.) 3. I'm kind of assuming the victim had a European style door lock, which can only be locked from inside, rather than American style door lock, which can be locked before exiting. But if it's true that it was a lock-from-inside style lock, then there is something wrong with the prosecutors. The prosecutors implied there was no w
From the room which was ransacked? If so, this would change my assessment of that aspect of the staging issue. It seems you are under the impression that the ransacking and broken window were in the victim's bedroom. As far as I know, that's incorrect.
Regardless of whether a break-in was actually staged (I don't care), have you ever had your home burgled? I have; they took a few dollars worth of laundry quarters in plain sight, rummaged through some random areas (some drawers, shelves, under the bed, and neglected to take anything else, including electronics, cheap jewelry, and a few hundred dollars cash in a desk drawer.
Never (as far as I know).

I'm a bit curious about something:

If read your post correctly, you feel that you can discount as pretty much irrelevant the opinions of quite a lot of people (jurors, police, etc), on the simple basis that people can be spectacularly wrong on occasion. ( I'm really not sure about this.)

In fact, as far as I can tell, you start from “clean” priors and do all your updating based only on the “physical evidence”; no opinions entering your calculation.

This seems almost OK, but something's nagging at me: how can you obtain thirty bits of confidence in your estimate using only evidence received from other people, via the Internet?

I'm also not sure about this, but your post seems to imply that a “good Bayesian” would be expected to assign that amount of confidence to his answer after only a couple of hours of surfing the Internet. I'm not saying that's impossible, but it really sounds very unlikely to me.

I'd very much like to see a chain of numerical reasoning that reasonably puts a 1:1000 upper-bound on the likelihood that Guédé is innocent, without starting with implicit assumptions of 100% certainty about data read from the net.* If you think an hour on the Internet is enough to reach t... (read more)


Having review your evidence and some other evidence that I was pointed in the direction of I have to admit I may have been wrong. Knox and the other guy are probably innocent.

There were a few things that lead me to my original conclusion: -The DNA evidence -Amanda changing her story -My belief that it was ridiculous that the police would go to all this effort to frame them if they were innocent.

The DNA evidence has been refuted, I can't say I understand this but I'm willing to accept there is a lot of doubt there.

Amanda changing her story seems like evidence that she is a liar and seems a ridiculous thing to do if you are a murder suspect. (I still think it was really stupid of her and totally the wrong thing to do.) But at the the time she wasn't more of a witness than a suspect and she possibly believed that this would get her off the hook and out of interrogation.

The third point about the police conspiracy is the most interesting. I have a huge bias against conspiracy theories. As soon as anyone starts to go "Wake up sheeple, you're being controlled." I immediately switch off. The quote you use from me at the beginning of your article is partly a referenc... (read more)

That original theory was based on Knox's testimony-- at that point it wasn't unreasonable for the police to accept it.
Unless they fed the testimony to her based on a text message that said "See you later." And frankly the conspiracy between the three of them and Knox's active participation in the murder wasn't in the testimony (as far as I can tell) she just reported recalling images of her boss associated with the screams of Kercher. At most it was just a confession to being at the scene.

Wasn't there a post here a while back that talked about how anyone positing a confidence of 0.999 on something non-trivial was most likely to be suffering from their own cognitive biases?

Good points, marred by what appears at first blush like double standards. Why are you willing to selectively discount some DNA evidence while you admit other ?

You say "the supposed Sollecito DNA on Meredith's bra clasp just plain does not count" - what is that "supposed" doing in here ? The FOA site admits that the clasp was shown to carry small amounts of Sollecito's DNA.

Why does it "not count" ? Admittedly, the handling of that evidence may not have been up to the standards normally demanded by the judicial system, but why should that matter to a Bayesian analysis ? All we're interested in as Bayesians is the ratio between P(DNA on clasp|Sollecito guilty) and P(DNA on clasp|Sollecito not guilty).

The defense may well have its own convenient narratives about how Sollecito's DNA "could have been transferred to the fastener in any number of ways" owing to carelessness on the part of the police. Those narratives are just as much noise as all the other noise you've pointed to. The details of US Department of Justice guidelines for forensics are also burdensome details for the defense.

The danger of coming across as arrogant - that is, more confide... (read more)

The Friends of Amanda site claims: If that is true then it suggests to me that finding Sollecito's DNA as well is not very strong evidence for anything.
Can you explain your reasoning here, in terms of P(other folks' DNA on clasp|Sollecito guilty) vs P(other folks' DNA on clasp|Sollecito not guilty) ? I can understand how this fact might be "suggestive" of something, but "suggestive" is the same kind of thinking as "suspicious": it's narrative rather than analytical.

It seems to me that the prosecution's case against Sollecito relies quite heavily on the evidence they claim proves he was present at the crime scene since they have no other solid evidence against him.

The reasoning used by the prosecution is basically what Jaynes calls the 'policeman's syllogism' in Probability Theory: The Logic of Science. The reasoning is of the form:

  • If A is true, then B becomes more plausible
  • B is true
  • Therefore, A becomes more plausible

Here A is (Sollecito was present at the crime scene) and B is (DNA tests on the bra clasp detected Sollecito's DNA). If we use C to stand for our background knowledge then by Bayes theorem:

p(A|BC) = p(A|C) * (p(B|AC) / p(B|C))

The premise of the policeman's syllogism "If A is true, then B becomes more plausible" takes the form

p(B|AC) > p(B|C)

And by Bayes theorem if this premise is true then:

p(A|BC) > p(A|C)

as stated in the syllogism. Now the significance of the evidence B depends on the magnitude of p(B|C) - the only way finding B to be true can greatly increase the plausibility of A is if p(B|C) is very small relative to p(B|AC). In other words, the prosecution's argument rests on the background ... (read more)

Now that is analytical. And by and large I agree with the analysis - that is, I agree that how much weight to give to that particular evidence is determined by your estimates of P(B|AC) and p(B|C). We may yet disagree on these, but if we do it should be on the basis of models that further evidence can in principle confirm or rule out, for instance whose DNA exactly was found on the clasp - does it match the investigators' ? They were at the crime scene. Contamination of that sort would help (in a Bayesian sense) the prosecution, not the defense. What I take issue with is to say that something "does not count" when we have a previous commitment to take into account every bit of evidence available to us. Either we use Bayesian standards of inquiry, or judicial standards of inquiry, but we do not cherry-pick which is convenient to a given point we want to make.
Very well said.
Check out the blog ScienceSpheres by Mark Waterbury. He discusses at length the issues of negative controls, field controls, and pinpoints the problems with the LCN DNA analysis. One of his key points is that the mistakes in the evidence gathering and testing aren't hit or miss - they are consistent - which reveals a pattern of intention.
Why are you willing to selectively discount some DNA evidence while you admit other ? Because the 2 key pieces of evidence should be discounted because they were not arrived at by using the same type of test and were collected differently. All the other DNA testing was done using standard DNA testing in a lab that was nominally set up to do it but which did not always follow all guidelines and procedures and who did not release all data for defense experts to evaluate. NO DNA that helped the prosecutions case was found initially on the 2 items... the bra clasp and the knife. Regular testing on the rest of the bra had strong findings for Meredith and Rudy. Amanda's DNA was on the knife handle and the bra clasp did have Meredith's as well. Now the problem comes... the DNA specialist then attempted doing what amounts to Low Count Number (LCN) DNA test which is still experimental in most places and while now accepted in the UK it requires a very specialized expensive lab that must meet many stringent minimum requirements. The tester in this situation had never done this before, the lab was fundamentally lacking in every way to do this test and come up with verifiable, trustworthy data. And yet they did allege that they found MKs DNA or something like it... on the knife... not blood.... no blood on the knife. The DNA would have been in picogram amounts originally and easily contaminated in that lab or elsewhere by the smallest flecks of skin or dust. And there are the same problems with the bra clasp except that along with RS's alleged DNA there are 5 other peoples... unidentified. There can be little doubt that all the DNA and "all" is a very very tiny amount, much smaller than regular standard DNA can reliable even detect as being there... Add to that no control tests were done and the "evidence" involving these 2 items evaporates. They are rightly to be judged differently from all the other DNA evidence. This looks like a DNA fishing expedition done after no DNA e
the LCN dna test was only done on the knife; the bra clasp was a regular DNA test, i believe.

You're even more overconfident than Eliezer. Even he didn't say that the probability of guilt should be less than 10%.

Also, you ignored the evidence of the scene being rearranged. As far as I can tell, there was substantial evidence of this, and substantial evidence of it being by someone other than RG. This implies substantial evidence that someone else was involved. Even if this doesn't necessarily imply AK is guilty, it definitely implies a probability higher than the original prior (which itself would be much, much higher than the probability you assign of 1 in a 100,000, given the proximity of the persons).

Basically, you are overconfident if you assign less than 10% chance of guilt. And the fact that your opinion is much more extreme than anyone else's doesn't show that you are more rational, but is very strong Bayesian evidence of overconfidence bias on your part, since it is well known that humans are naturally overconfident, not underconfident.

"Also, you ignored the evidence of the scene being rearranged. As far as I can tell, there was substantial evidence of this, and substantial evidence of it being by someone other than RG." I agree. And also substantial evidence that someone was trying to make it look as though the crime was done by an outsider.
The Friends of Amanda site clearly stated that there was no evidence of cleanup and that "cleanup" had only been referenced in passing in the trial, and the prosecution did not pursue the point. That is, there is not "substantial evidence" of the scene being rearranged, I'm not sure where you're getting that.
Yes, it made that claim, but as far as I can see it was wrong. Among other things, the bloodstains on her bra and her body indicated that her bra was removed some time after her death. Even by itself, this implies someone rearranging things. Likewise, luminaled footprints, whether or not they were Amanda's and Sollecito's as claimed, proves that someone cleaned something.
Those who say Guede left quickly and therefore was not around to remove the bra, shift the body later and place the cover over her after the blood was dried... forget that she was killed resisting rape and he very likely stayed to complete what he started. Rudy had plenty of time before he was seen at 2AM in the Disco to first clean up the mess that would have been in the way for what he did next (and by that I mean not only blood but the results of relaxed bowels and urethra) cut off her bra and lay her on her back adjusting where she lay so that he could enjoy what he set out to do originally. That is have sex with her... and he used condoms. And then still time to clean himself up, swab the obvious signs in the bathroom, throw the cover on her and lock the door. The patrons at the disco who saw him dancing between 2 and 4 AM said he stank very badly....
"luminaled footprints, whether or not they were Amanda's and Sollecito's as claimed, proves that someone cleaned something" No it doen't. Luminal doesn't reveal blood EXCLUSIVELY. I read somewhere, sorry, can't remember where, that it can also light up things like just sweaty/dirty footprints, no blood necessary.
You're absolutely correct. Not only that, but the Luminol footprints specifically tested NEGATIVE for the presence of blood. Every single one of them.
"If Luminol is used it can destroy important properties of the blood. While it can detect even small amounts of blood, the disadvantage is often that the small amount identified is diluted further by the Luminol solution. For these reasons, Luminol is encouraged to be used as a last resort in crime scene investigations to protect the physical evidence." Read more at Suite101: Luminol - Chemiluminescent Blood Detector: Forensic Investigators' Essential Tool for Crime Scene Investigation |
I Luminoled your bathroom. There were bloody footprints everywhere! Yeah, I didn't find any actual blood, but like you said Luminol can dilute blood. Who did you kill in your bathroom Pat? How could you do such a thing?! You monster!

I've wanted to reply here for a good while, so now that I've finally emerged from Lurkdom, I might as well do that. Great post!

Think about what you're doing here: you are invoking the hypothesis that Amanda Knox is guilty of murder in order to explain the fact that she hung up the phone after three seconds.

That was beautiful. Probably the single most important sentence in that whole article, at least in terms of convincing me to your reasoning.

I have to say though, at least one thing you say sounds not just overconfident but blatantly partisan:

known to have had utterly benign dispositions prior to these events".

I wonder how you could know this. If you picked it up from any pro-Knox source of information, it strikes me as a safe assumption that such a source would paint the defendants as angels regardless of the truth.

I'd also like to ask, how necessary to your argument was using that Jesus example? That's preaching to a very narrow choir, even considerably narrower than just "atheists". If that's what you wanted then no problem, but I'm thinking about the lost potential of this article to be persuasive to a more general public. This would be a great article to link friends to if it didn't rely on, not just the tools of rationality, but on specific conclusions shared by (I presume) most lesswrongians.

Thank you! Though I would probably write it differently today, it remains my favorite post, in the sense that upvotes and positive feedback on it make me happier than on anything else I've written here. Perhaps, but remember that this isn't something like a political issue, where there are always advocacy websites on both sides. Very few defendants X even have "pro-X sources of information" to begin with -- even if they're privileged (which is not particularly the case of Knox, by American standards). And even when they do, it's often because the case has (or is perceived to have) political implications, and the support is politically-themed. In my view, availability bias resulting from hearing a lot about those types of cases results in an underestimation of the evidentiary value of advocacy on behalf of a defendant like Amanda Knox. But, remember in any case that we have plenty of anti-Knox advocacy to contrast it with, in addition to the numerous media sources (now including several books) that attempt to be more "neutral" (though often fail). And there just isn't anything bad that anyone can actually find, despite many people trying really hard. The best the anti-Knox folks can do is to come up with their own highly sinister, distorted interpretations of Knox's and Sollecito's personalities, not shared by anyone who actually knows either of them. The absence of objectively negative anecdotes is conspicuous. Meanwhile there are all kinds of good things that have been said about both defendants by people who know them. Not necessary at all; it was indeed basically an applause light for this particular audience. Of course, there wasn't anything actually wrong about it. And the point I made with it was important: social consensus can't be trusted, or at any rate is very easily screened off. But yes, the post was definitely targeted specifically at Less Wrong readers, as opposed to the general public. Though I've been surprised at how little negative reaction the

How much does the choice of words bias peoples' thinking?

"Lone wolf theory" - If you google this term, what comes up is, sadly, the Amanda Knox case, and then terrorist cases like the DC sniper and the holocaust museum shooting. Rudy was not a terrorist, so some people may unconsciously dismiss the likelihood that he was a "lone wolf." And although it's a "theory," the phrase "Lone Wolf theory" sounds like something nutty, whereas it's really the normal scenario in such murders. The onus should lay on disproving this scenario, not proving it.

"Cartwheels" - Amanda Knox is said to have done cartwheels during her interrogation. Cartwheels have a connotation of joy. To prove my point, if you google "cartwheels of joy", it gets 82,400 hits. If the police had chosen the term "gymnastics," then it might be easier to understand why a young girl cooped up for 30 hours might engage in such behavior. Even if she did cartwheels and only cartwheels, she wasn't joyful.

"Foxy Knoxy" - Amanda's character was assassinated by the press long before her trial, and this catchy phrase was responsible for much of it. Ironically, the phrase came from Amanda Knox herself on her Facebook page, according to one of her old friends who stood up for her character.

Words played a powerful role in bias in Amanda's case. I don't think I even need to qualify that as my opinion.

No different from the prior, which is dominated by the probability that someone in whatever reference class you would have put Amanda into on January 1, 2007 would commit murder within twelve months. Something on the order of 0.001 at most.

Out of one thousand criminal trials in which the Less Wrong conventional wisdom gave the defendant a 35% chance of being guilty, you would expect to be able to correctly determine guilt nine hundred ninety nine times?

Maybe I'm missing something, but I think you read that wrong. komponisto said the evidence should not cause anyone to change the prior probability much. Surely, for people in AK's reference class, the per-year probability of committing a 3-party sex killing is less than 0.001? I think komponisto quite correctly described the effect of privileging the hypothesis, which might be what caused the LW community to be so much off from his estimate. Everybody seemed to be going backward from assuming AK's guilt at 50-50, whereas komponisto went forward from the background probability.
komponisto should not be going forward from the background probabilities because he isn't an experienced investigator with access to the crime scene. he's just a guy reading about evidence on the internet. a more reasonable prior for him to start with is, ''how often are people convicted of murder when they did not in fact commit a murder?'' (there are actual #s for this, too) when juries sit around thinking, ''is this person guilty or not?'' they assume the investigators working on the case are competent. they assume, quite rightly, that there must be a damn good reason why reasonable investigators couldnt quickly dismiss a hypothesis with such an insanely low prior probability. readers should do likewise.
I think I can see why. komponisto pretended to be a juror following the "innocent unless proven otherwise" mantra and updating on the evidence presented in the court. We, on the other hand, did what komponisto challenged us to do: figure out the answer to his riddle using the two websites he gave us. This being a riddle, not a court, we had no reason to favour one hypothesis over the other, hence the 50-50. That being said, I did favour one hypothesis over the other (my stated priors were 75/75/25) because at the moment I paused to write down an approximation of my current beliefs, I had already updated on the evidence presented by komponisto himself in his post, namely, that there was a trial against AK and RS. Maybe the reason why many of us gave so much importance to the fact that those particular individuals were on trial for murder was because it was our very first piece of information; and I don't think it's right for rationalists to do that.

I'd like to suggest another type of rationality test for this site. The top contributors should randomly make posts that are flat-out wrong to see how they are received; and they should also randomly make legitimate posts under different names.

When moving from my real name to this more anonymous persona the responses to my comments were noticeably different. This effect diminished over time. I've actually considered creating mechanisms by which I could make a self-blinded test of the effect of names on reception, but this was more with OkCupid in mind. Perhaps because investigating human psychology is even more fun than the dating itself.
Could you elaborate?
Sure. I'll compare what I perceive to be the differences between wedrifid now and, say, < 100 karma wedrifid. The difference in reception was more apparent given that wedrifid didn't have the steep learning curve associated with learning a new micro-culture. * Comprehension. Comments by young wedrifid were less likely comprehended than comments of approximately equal quality now. Not understanding people is a signal of high status. It obliges the lower status people to spend effort to second guess your way of thinking and adapt towards your preferred set of concepts in order to communicate with you. This signalling appears to run deeper than an outward display. Higher status people at times seem actually unable to comprehend things that would otherwise be in their grasp, often to their own detriment. * Rebuttal. People were more likely to reply with retorts to upstart-wedrifid and, more significantly, provided less or lower quality reasons when doing so. This is to be expected less from high status people and more from people with more moderate status who would like to raise it. (There isn't much point going one up if you have to reach 3 down in order to do so.) I get less replies now that I consider to be absolutely idiotic. Again, I don't think that is just because people generate inane nonsense then decide whether or not to post it by whether they recipient is a newbie or for some reason other reason an easy target (eg. out-of-group or currently being scapegoated). I think the calibration of carefulness is built in to the rebuttal generation system. Of course, I don't know how much of my perception is just me seeing what I expect to see: normal social behaviour. I also don't think this effect would be sufficient to overshadow a top level post by a renamed Yvain or Eliezer. I would probably just wonder who this amazing new poster was. I still remember Yvain catching me by surprise with that burst of brilliant posting in LessWrong's early weeks. Those seem to b
2Paul Crowley14y
Eliezer has made it explicit on several occasions that he never does this. I'm not saying it's necessarily a bad idea, but he doesn't do it.
3Eliezer Yudkowsky14y
Aye, and I'll say it again just to be sure. If I want to say something that's not true, I write a story and put it in the mouth of a fictional character.
Another way to go about it is to be contributor-blind. That's what I do.
That's a noble goal but I'm sure you're aware that merely having the intent to avoid a bias does not necessarily confer immunity to that bias. Psychological research is full of examples of people still suffering from a bias even when they have been made aware of it and protest strongly that they are not under its influence.
I meant, as a general rule of thumb. I code/scan/whatnot for the logic, and then also avert my gaze away from the name. I check the name after I have my response for verification. I like to read things like the Wikipedia list of fallacies so it is an interest of mine. With so much awareness these days of perceptual error (and similar) I find that people over-correct the other way to adjust for it. But I understand that I may be influenced by the name and not know it though I really do block it out of my visual field - as odd as that may seem. I check for those kinds of things as a basic rule and tendency. But I love to be wrong and to be challenged, and I know I have areas to sharpen. Logic is very pleasing to me to the point where when someone points out a problem with mine, I feel pleasure. Okay, enough of my testimonial... I am just happy to find this great site! I love how specific everyone gets. A joy... :)

@OP: you have appealed to rationality in examining this case... then you come up with this:

"1. Negligible. No different from the prior, which is dominated by the probability that someone in whatever reference class you would have put Amanda into on January 1, 2007 would commit murder within twelve months. Something on the order of 0.001 at most. "

The FACTS include 1) the police came to "her house" and discovered a murder victim in one bedroom and 2) she was tried and convicted. You seem to have given these zero weighting in your final c... (read more)

While I have a sort of vague sense of disagreement with this comment, I voted it up, because I would be very interested in an example of Bayesian reasoning applied to the real world without having a truckload of given probabilities to work with. In particular, I don't know how one would take into account D_Alex's 80% while also taking into account more specific factors.
I had the same reaction. I'm strongly inclined toward the OP's position, but if you're going to excoriate everyone else for failing to "jettison [their] intuitive feelings in favor of cold, hard, abstract calculation", you should provide the actual cold, hard, abstract calculations supporting your own position.
I should have pointed this out earlier, but for the record: "cold, hard, abstract calculation" referred to the willingness to ignore quantitatively weak evidence even though it "feels important" to you; it did not refer to some specific back-of-the-envelope application of Bayes' Theorem. (And "excoriate" is definitely not the right word here, at least with regard to the LW community.)
I'm curious where in the world you get this "fact". I don't believe that at all (and it seems essentially unverifiable). Also, remember that Knox isn't a random person convicted of a crime: most of them don't make international news. Also, Italy does not have the same rights and freedoms as the US: for instance, they don't have separation of church and state.
2Paul Crowley14y
The only test I can imagine is: when a new technique, like DNA testing, comes along, test a random sample of cases to which it is applicable. Unfortunately the cases re-examined are very carefully chosen, so no such information is available.
Thanks for that link. I don't understand why the plea bargain rate is at all relevant. Prosecutors try to dispose of most cases through plea bargaining, and paying a fine may be cheaper than paying legal costs for many people who plead guilty. I don't see any reason why an innocent person would be any less likely to plead guilty. The innocence project focuses on high-profile murder and rape cases where DNA evidence can be obtained, so it's very non-representative of the criminal justice system as a whole. Also, this ignores the question of legal justifications and excuses, and other defenses like illegally obtained evidence. If, as a matter of fact, you killed someone, but the evidence was obtained illegally, and you're still found guilty of murder, that's still a wrongful conviction.
The part relevant to my earlier post was: "....even if juries get it right only 80 percent of the time (an assumption at which most sensible scholars would cringe).... But the real wrongful conviction rate is almost certainly lower, and significantly so ... ".
"I offer $50 to the AK defense fund..." Has the offer been amended from $50,000 to $50 since last night, or did I just misread it at 1:00 AM? A shame, because I was looking forward to seeing the attempt.

I know this is an old thread, but for any people just now reading it, I thought I'd pass along this bizarre development.

See discussion here.

(Beginning thread for a debate with Rolf Nelson. Others also welcome to comment, of course.)

Okay, Rolf, so to get things started, I'd like to get your numbers out on the table. So, if you wouldn't mind, please tell me, first of all, your current posterior probability estimates for the guilt of:

  1. Amanda Knox
  2. Raffaele Sollecito
  3. Rudy Guede

(I expect we'll mainly focus on Knox and Sollecito, since that's obviously where our main disagreement is; I've included Guede for the sake of comparison.)

Next, I'd like to know your priors for Knox and Sollecito (and Gued... (read more)

Oh, let me play! (When you made your first post on this issue I found trying to look for unbiased information a terribly frustrating experience so I didn't look for more than 20 minutes, and haven't done any reading on it since, except for a cursory look the the wikipedia page just now. A list of all points that are agreed on by both sides (with sub-points arguing about the relevance of the point from both perspectives, perhaps) would have been very welcome) Current posterior: not really sure, let's see what I end up with below, but as a starting point: 0.01<P(S) < P(K) <0.2 < 0.8< P (G) < 0.99 Priors for commiting a homicide in a specific month: P(K)= 4.7 *10^-6 (US homicide rate, assuming being female and a young adult roughly cancel out) P(S)= 4 *10^-6 (Italian homicide rate assuming young adult males are 4 times as likely to commit murder as average) P(G)=1*10^-5 (had been implicated in a break-in) An inhabitant of the top floor of that apartment being murdered in her room in this same specific month (R): P(R|K)=0.1, P(R|~K)=4.5*10^-6 P(R|S)=0.04, P(R|~S)=4.95*10^-6 P(R|G)=0.0005, P(R|~G)=5*10^-6 Guede's DNA being found all over and inside the victim of a homicide in this same specific month (D_G): P(D_G|K)=1*10^-4, P(D_G|~K)=6*10^-7 P(D_G|S)=5*10^-5, P(D_G|~S)=6*10^-7 P(D_G|G)=0.6, P(D_G|~G)=1*10^-7 I can't think of any other pieces of evidence that I can treat as effectively independent. Given R and treating the probability of any murders except R as effectively 0: Knox' DNA not being found on the victim (D_K): P(D_K|K)=0.5 P(D_K|~K)=0.8 P(D_K|S)==0.85 P(D_K|~S)=0.81 P(D_K|G)=0.82 P(D_K|~G)=0.82 Sollecito's DNA being found on bra clasp of the the victim, but nowhere else (D_S): P(D_S|K)=0.0002 P(D_S|~K)=0.00006 P(D_S|S)==0.001 P(D_S|~S)=0.00005 P(D_S|G)=0.00007 P(D_S|~G)=0.00007 Minimal trances of R's DNA found on the blade of one of the knifes in Sollecito's kitchen possibly matching one of three wounds, along with Knox' DNA on the han
One of the lessons of this exercise, that may be worth stating explicitly, is that there's no "outside referee" you can look to to make sure your beliefs are correct. In real life, you have to make judgments under uncertainty, using whatever evidence you have. It's not as hard as you (and others) think. Yes, of course, the sources are "biased" in the sense that they have an incentive to mislead if they can get away with it. But what they say is not literally all the information you have. You also have background knowledge about how the world works. Priors matter. If A says X and B says ~X, and there's no a priori reason to trust one over the other, that doesn't mean you're stuck! It depends on how plausible X is in the first place. Here's the real lesson: Bayesian calculations are not some mysterious black-magic technique that you "apply" to a problem. They are supposed to represent the calculations your brain has already made. Probability theory is the mathematics of inference. If you have an opinion on this case, then, ipso facto, your brain has already performed a Bayesian update. The mistake you made was not making up numbers; it was making up numbers that, as you point out in the end, didn't reflect your actual beliefs.
I meant that questions that should have an easily determinable answer, like "Did someone clean the blood outside her room up before the police was called" were unreasonably difficult to settle. Every site was mixing arguments and conclusions with facts. Sure, it's possible to find the answers if you look long enough, but it's much more work than it should be, and more work than I was willing to invest for a qestion that didn't interest me all that much in the first place. The brain doesn't operate with very small or very big numbers, though. And I doubt it operates with conditional probabilities of the sort used above, as far as it operates Bayesian at all I would guess it's more similar to using venn diagrams. The point is that I didn't spot that until after I did the calculation, and while I don't usually do much in the way of statistics I intuitively got the simple Bayesian problems like the usual example with false positives in a medical test right before hearing about Bayes theorem for the first time, so I don't think it's because I'm particularly bad at this. If you need to tweak afterwards anyway doing the Bayesian update explicitly isn't very useful as self-control.
The disagreement most likely stems from the reliability of the Micheli Report for accuracy and comprehensiveness.
The disagreement most likely stems from the reliability for accuracy and comprehensiveness of the Micheli Report.
Posterior probability estimates: 1. 0 2. 0 3. .9 Priors: 1. .01 2. .01 3. .5 Is that the sort of thing you are asking? I don't know if I attributed correctly.
Anna: for the context of this, see here. You may want to remember that 0 and 1 are not probabilities. Also, I must say I don't understand your extremely high prior of 0.5 for Guede. (The evidence against him is such that the prior could be much, much lower and he would still have a very high probability of guilt.)
The thing that I am trying to point out is that I believe Amanda and Raffaele were wrongly included in the class called "suspects".
Yes indeed -- our term for that here is privileging the hypothesis.
(Although I do find the point more salient when it is described explicitly rather than by reference to jargon. )
Wasn't trying to enforce the use of jargon so much as classify the fallacy. After all, the point is even more salient when you can relate it to a whole category of error found in many other contexts.
I find the term useful. I think it is what a lot of the media has done. Since Amanda and Raffaele are in discussion and named in the theory, there must be something to it and they have equal weights of measure for concern as the third suspect, Rudy. When in fact, they are very lightweight and the (heavy) weight should be attributed to the method by which they became suspects. The term helps me to say "Oh that's what is going on." Like komponisto said, a whole category of error. (Not to mention all the contexts apart from this specific case, the topic at hand, indeed.)
Quite right. It's actually amazing how little attention was paid to Rudy Guede in the media coverage of this case, particularly in the U.S. and U.K. media. (Numerous stories either omitted all mention of him altogether or else referred briefly and vaguely to "a third suspect" -- without any hint about the disparity in evidence.)
I am also pointing out that is a question pertaining to applied situation with a limited scope - the decision to convict or exonerate. For all intents and purposes, relative "knowing" is permissible in a legal case, since we are dealing with human events and activities of a finite nature - a court decision is a discrete (not continuous) matter. After a certain point, probabilties have to turn into decisions.
Therefore, I offered 0 in the spirit of Goedel's completeness theorem, yes, at the expense of consistency. Consistency will yield a perpetual motion situation. Completeness is required and can be appropriately reached through reasoning, logic, objectivity, etc. Something can only consistent OR complete. Not both.
In other words, his psychological profile and actions leading up to the murder do not indicate that he was above board and immune from a violent attack, especially an attack with a knife. He was also known around town to go too far in the direction toward harassment of females around town at the clubs and so forth. He was also known to do various drugs including aggression-increasing drugs such as cocaine. He was known to break and enter and steal, and that he carried a ten inch knife "for protection" (his words). It could be argued then that it was a matter of brief time for him to break and enter, steal, and encounter someone indoors in the process as was arguably such in the situation with Meredith, and "defend" himself when caught or interrupted. This is the case that I would start to make as for a high prior.
It is true that a high probability of a prior is not necessary for probability of guilt. It is also true, however, that it doesn't mean that he didn't have a high prior. I could drop it to .3 though. With the actions in the previous weeks, a case could be made that he was in an escalating pattern of behavior, which is why I gave him a .5 prior.
Thank you. Yes I've seen the post by Rolf Nelson. I don't understand (though I admit for expediency's sake did not fully read the 0/1 link which I should do if I post here) how there cannot be an absolute for innocence. I didn't assign 1 to Rudy Guede for the reason you mention. But in terms of innocence, we know for example that Princess Diana didn't kill Meredith and that the mayor of Seattle at the time did not kill Meredith, so how can it not be zero? I wrote zero for a specific reason. I wanted it to indicate that gap between reasonability of arrest and no reasonability of arrest. To assign even a small possibility at this point seems inaccurate to me. Although, you make a good point, in actuality, so I would amend them to .001. Is that a proper probability quotient in terms of the question?
Yes, that would be more reasonable (indeed, it's about where my own estimate is).
Is it possible to show that it would be impossible for them to have been participants making it 0? Is there anyone in the world in that class - of 0? Trying to understand the parameters of "probability".
I agree with Alicorn - a probability of 0 or 1 can only be legitimately used as hyperbole. (There's a technical explanation for why to exclude probabilities of 0 and 1, but it assumes you have studied and understood Bayes theorem and know how to think about probabilities in real life in Bayes terms.)
Exactly-0 isn't on the table at all. Close-enough-to-0-that-you-can-represent-it-that-way-without-too-much-disclaiming is reserved for propositions like "a square circle and Batman teamed up to, not kill, but kidnap and replace with a convincing inert android, Meredith". Princess Diana's odds of having killed Meredith are miniscule, but not zero or even compellingly zerolike, compared to those.
I don't know if this means I disagree with Eliezer but I'm pretty sure the probability of a contradiction has to be 0 and the probability of a tautology has to be 1. Else really weird things start happening and you can't do deduction. Like, what is the probability of A given A ^ B?

*cackles evilly and cracks metaphorical knuckles*

The circle is defined as the locus of points an equal distance from a center on a plane. A square is defined as a regular quadrilateral - i.e. a shape with four sides of equal length separated by four angles of equal magnitude. If you allow that "distance" may be generalized) to be applicable to other geometries than Euclidean...

...what is the shape of a circle on a chessboard, where "distance" is measured by the number of king-moves?

I believe this is a useful object lesson in the difficulty of constructing properly impossible propositions.

Edited to make the square have four sides, not three. What was I thinking...?

And when you superimpose a middle finger onto Reimannian space... Edit: But upvoted because it is always good to get this reminder.
Something can be metaphysically/logically impossible without it being okay to assign exactly-0 to it. Epistemic probability is what we're really representing here - I mean, even something as uncertain-to-me as the current weather conditions in the red spot on Jupiter is exactly one way. But it's not useful to represent that single-ness of weather conditions because I can't access them. I similarly can't usefully access absolute epistemic certainty about even simple math and logic. I'm a broken machine; I cannot handle perfect surety.
It isn't that simple. Most of the results we get from Bayes theorem we get by deduction. For example, the Dutch book argument, the most common justification given for Bayesian epistemology in the first place, relies on deduction. So does nearly every other important result we get from Bayes theorem. So when you say to someone: take this evidence and act rationally that may imply that that person not get her deductions wrong. This is why, afaict most Bayesians assume logical omniscience. See here. Apparently there have been attempts to weaken logical omniscience and maybe someone here has one in mind... but I haven't heard it. Obviously it is that case the humans, as a matter of psychological fact can screw up deduction. But this is basically like saying that as a matter of psychological fact humans aren't perfect Bayesian rationalists. The whole theory isn't supposed to be descriptive, it is an ideal to strive toward.
I have also seen Eliezer tempted to consider a '0' probability in response to a 'divide by infinity' situation. (I think there is a 'mathsy' way to represent that kind of '0'.)
That's called a limit). What's special is not the “zero” but the “infinity”: you don't talk about a value “infinity” (attempting to have one causes you to lose various other useful properties), but rather that as some input increases without bound, the output approaches zero. “The limit of 1/x as x approaches infinity is zero."
The concept of limits is a great way to look at this. A limit is a thing unto its own, a complex statement indicating, confirmed as much as is humanly possible. Another notion is what Goedel brings to the table. His contribution of something being consistent or complete is relevant.
Well, it is quite fascinating that no one gets a 0 probability. Just to ask, does Meredith get a 0 probability? I will move past understanding the exclusion of 0. I just want to make sure I understand. Anyway, when I say 0, I understand it to mean functionally 0, which is the same as .0000000001, which is also functionally 0, correct? Thank you for you patience.
Meredith could have committed suicide. She's probably more likely to be responsible for the death than Princess Diana. And she's much more likely than the team of Batman-and-square-circle.
Were there any fatal wounds that she could not have inflicted?

Well, maybe she had superpowers. Or was killed by her time-traveling past self. When you get to probabilities this low, boy do you ever get to make shit up.

Maybe she was killed by her time-traveling future grandaughter. I was tempted to rule it out based off the anthropic principle (I don't expect to exist in a world in which someone was killed by someone who wouldn't exist if the victim was killed). But come to think of it I haven't assigned 0 to specific operational mechanisms behind time travel.

Negligible. No different from the prior, which is dominated by the probability that someone in whatever reference class you would have put Amanda into on January 1, 2007 would commit murder within twelve months. Something on the order of 0.001 at most.

Suppose it were somehow revealed to you that three people had in fact committed the murder. Would you still maintain that K and S are no more likely to have been involved than anyone else in the relevant reference class? If not, doesn't this suggest that this quoted bit is an overstatement?

That's a genuine question; I haven't fully thought that concept through.

There is a proximity effect, just as in the actual situation K's probability is slightly raised by the fact that a killing occurred in her house (and S's is in turn raised by his intimacy with K). But the evidence against G utterly destroys her explanatory value, and brings her probability back down to the prior. No, because this is my posterior probability after taking into account the evidence against G.
This is true in reality, not in my hypothetical. If it were a fact that three people had been involved, as posited, the evidence against G would not explain anyone else away on its own. I'm using a counterfactual to attempt to show that your claim that there's no special evidence of her guilt is false. You've stated: [A] P(Knox is guilty) = P(Random person from relevant social circle is guilty). It seems to me that [B] P(Knox is guilty; given multiple killers) > P(Random person from relevant social circle is guilty; given multiple killers). Assume [B] is true. The additional specification does not point to K, it only says that people other than G are guilty. Therefore, [A] should be false. So, I'm assuming you would take issue with the truth of [B], or else with my reasoning, and I'd be curious as to how and why either way.
the issue at stake is P(multiple killers) being very small, and P(knox guilty) - P(random person guilty) is less than zero due to the P(G guilty). Or at least that is how I would weight them.
Given that someone was killed, the probability of multiple killers is not "very small", according to statistics. Definitely not more than 50% but definitely substantial (as I stated in another comment.)
[A] is only true given the evidence against G. Not knowing that evidence, we would have P(Knox) > P(random peer) by proximity.
This is entirely wrong. The evidence against G should modify both P(Knox) and P(random peer that is not G) downward. Proximity should keep P(Knox) > P(random peer) unless there is evidence specific to Knox which lowers her P (i.e. a good alibi). Your statement about proceeding from the physical evidence and ignoring other things is a heuristic. The fact is that some random suspicious behavior by K is evidence against K, it is just extremely weak evidence. Let R = random suspicious behavior by K. I contend that P(K|R) > P(K|^R). Your arguments that many people do R all the time and are not murderers address the strength of the evidence, but do not address the sign, unless you wish to contend that people who engage in R are less likely or equally likely to be murderers than people who do not. You have made no such argument. It's clear that the evidence against K should be overwhelmed by the evidence against G, given that no solid connection was established between G and K. But it isn't zero evidence, it is merely very weak evidence. You have established a safety heuristic to keep yourself from overvaluing weak evidence, but your safety heuristic has it's own shortcomings, because it has caused you to give it zero weight, which is obviously wrong.
No, it is most certainly not "entirely wrong", if it is even wrong at all. Explanatory value is the only attractor of probability: there is nothing that can possibly raise P(Knox) except improbable facts that require explanation (where the amount of probability flow as a function of the improbability of the explanandum is governed by Bayes' Theorem). In this case, virtually all of the improbability of the data is contained in the mere fact of Kercher's death. But that fact is entirely and adequately explained by the actions of Rudy Guede; the evidence against Guede completely obstructs -- screens off -- the probability flow toward Knox. That is the argument made in the post. Nowhere did I say that evidence of Guede's guilt is evidence of Knox's innocence, in the sense of lowering P(Knox) to below the prior. But the evidence against Guede absolutely is evidence against the hypothesis that Knox killed Kercher without Guede -- which is most of the Knox hypothesis-space (and thus where most of the probability flow toward Knox arising from Kercher's death was concentrated)! (This point is especially important in view of all those comments from people saying that "the prior" should (already) take into account the fact that Kercher was killed. Well, if that's your prior, then it most definitely is lowered by the evidence against Guede!) When you make a statistical argument of the form "well, a homicide was committed, so there's some probability of multiple attackers", you're starting from a position of ignorance of the details of the case, and computing an expected probability over all the various scenarios where there exists evidence of multiple attackers. But here, we know the details of the case, and we know that there is scant evidence of anybody but Rudy Guede being guilty (at least, we do if we're capable of telling strong evidence from weak). Finally, these comments of yours represent nothing but uncharitable pedantry -- the Bayesian analogue of my pointing o
since you appear to still be watching this thread, it seems worth a reply even 3 months later. Clearly "entirely wrong" is too strong and unnecessary verbiage in any case. I admit it did not even occur to me that you were using "=" to mean only "essentially equal in absolute terms". Note, my comment was referring only to your response to Psychohistorian, not your general argument about why P(Knox) is very small given the information presented at trial, with which I agree wholeheartedly. I apologize for my confusion. Here and in a few other comments, you seemed to be asserting not merely that the strong evidence against G put so much probability mass into P(G) that the differences between P(Knox) and P(random peer) became much too small to care about in absolute terms, but that it somehow changed the relative dynamic between P(K) and P(rp). The fact that neither probability was worth worrying about in legal terms doesn't change the '>' vs. '=' question, and that's the only thing I was responding to there. I also suspect the distinction matters in practice in rare cases, so I saw it as important enough to be worth picking the nit.
Yes, I agree. Did you read this discussion before making this comment?
The percentage of murder cases that involve multiple murderers is relevant to the idea that the evidence against G "brings her probability back down to the prior," and this percentage is much higher than you think it is (i.e. it is higher than 1% of cases, and this is enough that AK's probability will definitely not go back to the prior. In fact it seems to be in 10-20% of cases),
That may be true, but many cases of wrongful conviction involve multiple innocent defendants. The Norfolk Four is a perfect example. At one point the police suspected SEVEN men of the attack, even though the coroner said there was only evidence of an attack by one person. In the end, it turned out one person, a known rapist, had committed the crime, but not before four of the innocent served over a decade in prison. For those who criticize Knox pointing the finger at Lumumba, again, look at the Norfolk Four case where the first suspect, innocent, wrongfully accused a friend, who then wrongfully accused several friends, who then wrongfully accused several of their friends! It might be impossible to understand the mindset that leads to something as wrong as falsely accusing someone else, but it's happened to a lot of people, and normally they are treated with far less scorn than has been poured on Knox by her critics.
This is accounted for in my updated estimates.
Ok, but given your updated estimates, it is consequently unreasonable to just dismiss psychological and interpreted physical evidence (i.e. bloody footprints, crime scene rearrangement and so on). Whether this is actually so or not, it is very possible that these things could add together to give enough evidence to say that someone is probably guilty; going from a 1% to a 99% chance does not take an extremely large amount of evidence. And this seems to imply that an hour on the internet does NOT beat a year in the courtroom. To know whether this is true or not you would actually have to know the evidence in more detail. For example it does seem that even in Judge Micheli's report there is a good deal of detail that has been generally unreported in English.
I don't see why this kind of stuff is any more powerful than its counterparts on the other side: K & S's benign personalities, lack of criminal history, lack of motive, etc.
That may be true. I read (I didn't pay attention to the source, it could be just a rumor for all I know) that AK sent an email to a friend, shortly after coming to Italy, saying that she had convinced a stranger to have sex with her on a train. If true that would show a dangerous kind of behavior, even though not criminal. Assuming she might be guilty (for the sake of argument) the most likely explanation would be that they were "playing around" and things got out of hand, not that anyone ever was planning to murder someone. In any case it seems my last point stands: the evidence as it has been presented to us may be unpersuasive but that doesn't mean that the same kinds of evidence couldn't become persuasive in principle, and this may be exactly what happened in the trial.

I'm ashamed to say I failed this one, and badly.

I'm new to the Way of Bayes, and I've been reading the sequences regularly (that's why I'm on this post, actually) and thinking I've been doing pretty well, but this illustrates that I have a long, long way to go.

I did do a whole lot better than the jury in this case, such that I would never have convicted Knox and her boyfriend, but I still came away with about a 60% probability of their having been guilty, with Guede at >95%.

I started with the pro-guilty website, and thinking back I clearly privileged t... (read more)

On the other hand, you'd be surprised at how difficult it is for people to understand this even after seeing the explanation. While of course it's always preferable to get things right on the first try, the fact that you saw it so clearly after reading this post places you in a high percentile for learning speed. (I know whereof I speak here, because I've spent some time arguing about this in other parts of the internet, only to be dismayed by the true extent of people's ability to clack. Heck, even here in the comments section of this post there are some pretty confused comments with depressingly high scores.) I think your analysis is excellent, and is an admirable example of "cognitive debugging". This part in particular is worth dwelling on: It is really difficult for people to discount information, and to actually update on evidence of the form "that information may not be reliable", rather than treating it as an "opposing argument" to be rationalized away, or simply forgetting it altogether. Something like the bra clasp provides an example of this: people hear about it, and decide that Sollecito is guilty. Then, when they hear the defense argue that it's unreliable, they mentally dismiss it as "the defense trying to poke holes in the prosecution's case". They may respect the social obligation to provide some sort of answer to the defense's arguments, but they don't consider that the defense arguments should actually impact their belief about whether Sollecito is guilty; the belief-formation process was over and done with at the first stage! It's not that they explicitly, consciously think like this, of course; rather, they have just failed to fully incorporate the "rules" into their unconscious belief-generating system. The third and fourth virtues are hard. I like the star-gazing-at-noon analogy, and may use it myself in the future.
That's what upset me the most. I made a special note of it, in order to give it a very low weighting, yet it was still a major factor in my assessment. It had to be, because the prosecution's case hinged on it. I think next time I notice something like that I will have to assign it a specific weight as soon as I decide that it should be given a low weight. Instead I just labeled it as "weak" in my head and moved on. So when I think "that's likely true" I should stop and consider what the actual number is that I would assign to it. This would help considering in spotting cases where I assign more than 100% total probability to an outcome. If I am thinking it is 70% likely that they are guilty and 60% likely that they aren't, there is an obvious problem. If I don't assign any numbers until I'm finished looking at the problem then I'll never spot this error, as I'll simply calculate not-guilty likelihood from the guilty likelihood. Much to think about and much to learn still.

A flurry of more recent comments, (concerning in particular the nature of evidence), plus some private message correspondence, provides me with an excuse to make what are probably somewhat-overdue comments succinctly summarizing the main points of this post, addressing the most important issues and objections raised by others, and tying up some loose Bayesian ends.

Objections raised to my arguments seem to fall mostly into the following categories:

(1) Bayesian pedantry: pointing out that weak evidence is distinct from zero evidence, that rational evidence ... (read more)

(2) Claims that I am too dismissive of psychological evidence. Some folks appear to have misunderstood me as arguing that psychological evidence can be dismissed out of hand by its very nature, or that Amanda Knox shouldn't have been questioned by police despite being Kercher's roommate. Obviously, neither is the case. First of all, psychological evidence, strictly speaking, is physical evidence. In fact, all evidence is physical. The question, always, is about how strong a given piece of evidence is. In the post, I mentioned two rules for this: (i) the closer the spatiotemporal connection, the stronger the evidence -- something which follows from the laws of physics; and (ii) high-prior data is at most weak evidence of a low-prior hypothesis (or: thou shalt not postulate a strange thing to explain a less strange thing) -- an immediate consequence of Bayes' Theorem. If a person's behavior were sufficiently unusual, it might constitute significant evidence they were involved in a homicide. And if a murder occurs in Knox's house, Knox is clearly one of the first people the police should interview. But the psychological evidence against Knox is in fact very weak: the causal linkage between Knox's cartwheels, phone calls, or speculation about Lumumba's involvement on the one hand, and a hypothetical murder committed by her on the other is very tenuous compared to the causal links between these things and more local factors which are likely to be largely independent of Kercher's murder. And yet, many people mistakenly believe the evidence is strong. Why? Because, for perfectly understandable evolutionary reasons, people are interested in psychology; it's salient in their minds, and they mistake this salience for evidentiary strength. They find it easy to imagine a guilty Amanda Knox doing cartwheels, and caught up in the narrative, forget to properly consider the ways in which an innocent Amanda Knox could also end up doing cartwheels. (In fact cartwheels were never so
(3) Object-level arguments from a few people who (still) think there is a significant chance Knox and Sollecito are guilty. There don't appear to be many LW regulars who assign high probabilities to Knox and Sollecito's guilt. There are a few who remain apprehensive about doubting the rationality of the jury or of people like Judge Micheli (the judge in the Guede case) to the extent of lowering the probability of guilt to single digits of percentage; but mainly, they agree that acquittal is called for. My remarks here will thus be directed mostly at people chancing upon this post from outside. It is incorrect to assume, as some people have, that because I didn't mention various facts about the case in this post, that I am therefore unacquainted with them. On the contrary. However, I do assert that the essence of the case -- the decisive information -- is just what I presented here. Among my main points was that people have been distracted by various other details to the point of getting the wrong answer. The central case in point would be the eight members of the Perugian jury, who despite hearing all kinds of information over the course of nearly a year, were unable to sort out the clutter from the essential facts, which are these: * The prior probability of Knox and Sollecito having committed murder is extremely low; of having committed this particular kind of murder, even lower. * Since Guede is unquestionably responsible, the mere fact of Kercher's death does not need to be explained. * There is no evidence that Knox was in Kercher's room on the night of the crime, and almost no evidence that Sollecito was. * There is almost no evidence of any association between Knox and Guede, still less of any between Sollecito and Guede. * There is no evidence of antipathy toward Kercher on the part of Knox or Sollecito, or of any other plausible motive for the crime. * Every piece of apparently strong prosecutorial evidence has either been totally discredited
Point-by-point: Given that AK's roommate is dead, a break-in was staged, and the coroner's report showed multiple attackers, the prior on AK being a murderer of Meredith is rather high. On the other hand, if we throw away all known evidence, the prior of AK (or Guede, for that matter) being a murderer of Meredith is less than one in a trillion. I claim the former approach, where you use evidence rather than ignore it when it's inconvenient, is preferable. [Edit: OK, that was too snarky. Let me instead say that you should start with a tighter prior rather than a looser prior where possible; it makes the math more tractable.] That said, I think our main disagreement is on whether the prosecutorial evidence holds up. 1. Why do you believe DNA evidence flies around so easily? Quick tests: Do you find your beliefs about DNA match up with how DNA is used to draw conclusions in any other court cases that you're familiar with? Why was RS and the other roommate's DNA not found in more areas? Google any video of a DNA testing lab. Are they wearing hazmat suits and, if not, why aren't the testers contaminating their own samples left and right? 2. I disagree the five pieces of evidence you listed (footprints, DNA-mixed blood, knife, bra clasp, cleanup) are discredited. I am interested in hearing why you personally believe each of them is not strong evidence. [Edit: if you limit yourself to one item, my order of preference is DNA-mixed blood, then knife, then bra clasp.)] 3. Outside of those five pieces of evidence, I also think you're being too dismissive of the other pieces of evidence. For example, why is Knox naming Lumumba a non-sequitur? 4. If the basic theory was that multiple people, including at least one roommate, killed MK, then there was no reason to abandon that basic theory upon discovering Guede. Am I correct in that one of our disagreements is this: Observation: AK claimed she saw Lumumba kill Meredith. Lumumba was therefore detained by the police bas

My ADHD brain lost interest in this after the huge discussion here covered pretty much everything having to do with the trial. And komponisto knows this stuff way better than I do so I'll let him respond. But nearly all of the regulars here looked at the exact same evidence you are bringing up now and nearly all of us eventually concluded that it was more likely than not that AK was innocent. Moreover, I specifically recall discussions of every single point you bring up and I believe every single one was resolved. So you might want to look back at the comments to the original post (the test of your rationality one) before you make komponisto go through all this again.

Since I was heavily involved in the discussion of the Lumumba 'accusation' I'll just add this: If AK and RS cleaned up their own involvement with the crime, but intentionally left the evidence implicating Guede wtf would AK not just accuse him to begin with? It seems likely bordering on obvious that AK was interviewed under duress, that the police had seen her text to Lumumba as implicating evidence and fed her his guilt. As a result, AK either made up or dreamed this bizarre pseudo-memory in which Lumumba was present.... (read more)

komponisto, can I just say that you have very eloquently voiced my very thoughts on this case. In my blog article, "Logic Trumps Innuendo" I wrote the following:

"As I surf the net, reading a variety of comments in regards to this case there is much speculation about evidence in this case. Much of it was not used at trial, but somehow made it into the public consciousness through ongoing press leaks during the investigation, such as:

"Knox was seen with a mop and bucket the morning of the murder." What does that mean exactly? The inn... (read more)

It seems to me that most of those problems can be explained by postulating that (1) the prosecution's case is overstated; and (2) the prosecution's scenario of what happened is incorrect. However, even if (1) and (2) are true, it does not mean that Knox and Sollecito are innocent or uninvolved in the murder. By analogy, consider the OJ Simpson case. As I recall, there really were some serious questions about the prosecution's evidence in that case. Even so, it seems pretty clear (to me) that OJ was guilty. Obviously the OJ Simpson case is very different from the Amanda Knox case. But the point is that police, prosecutors, and others are often tempted to try to turn a good case into a great case. Of course one big difference with OJ Simpson is that the case fits into a very simple paradigm: the jealous ex-husband. So it's very easy for the prosecution to present a coherent theory (including a motive). Perhaps a better analogy is the Annie Le case. It seems pretty clear who killed her, but it's not entirely clear why. Nevertheless, there will be pressure on the prosecutors to come up with a scenario for what happened and why.
There is a lot of what I call "noise" in this case. Things that MAY apply, but not all of them carry the same weight, thus it becomes necessary to organize my thought processes. I start with the hard evidence FIRST, not the other way around. I do not look at the people and then find evidence to implicate them, I look at the evidence first and then find the people. By "hard evidence", I mean that evidence that can be observed directly or by repeatable scientific methods. I refine my thought process even further by using these principles which state: 1. The simplest explanation that fits the facts is usually the correct one. 2. the more outlandish a theory is the greater the amount of evidence is required to support it, and 3. The further away you move from a causal event the less accurate your observations will be. With that as a guide, the DNA of Rudy Guede inside Kercher becomes a white hot beam of guilt, and Knox's cartwheels with the police has almost no luminescence at all. Given how much evidence is in the room where Kercher was killed leads you directly to Rudy Guede. The bedroom is the key to this case as that is where the murder took place. As you move further away from the bedroom, you are less likely to find direct connection to the killer or killers, so as I move out of the bedroom other things like mixed DNA in a bathroom of people who co-habituate get less consideration. Given the preponderance of evidence that there is of Guede, logically then, this must also be true for Knox and Sollecito if the prosecution's theory of the crime is to hold true. However, no such preponderance of evidence exists for them. Knox's presence is non existent according the the physical evidence, and Sollecito's hinges on a bra clasp found 47 days after the crime. The more outlandish a theory is the greater the amount of evidence is required to support it, ergo which version of the crime does the evidence and logic support: That a known burglar, involved in three separa
"That a known burglar, involved in three separate break-in incidents in the weeks prior to the murder broke in and robbed, assaulted and murdered Kercher. Or That new lovers Knox and Sollecito with no criminal history whatsoever, conspired with relative unknown Guede to involve Kercher in some sex game and inadvertently killed her?" Are those the only two possibilities? As an attorney, I can tell you I have seen many many cases where neither side's theory about events is very credible. It seems pretty clear to me that the answer to my question is "no," but I would like to hear your take.
As an attorney you are asking a tangential question with the implication that it has more relevance than it does.
I remember when I started practicing law on my own I would be outraged when I caught the other side in numerous lies and yet the judge would still go against my client. At the time, it seemed to me that the judge was heavily biased against my client. It took me a while to learn what I have tried to share in my last couple posts. In hindsight, I realize that most of those clients really did do pretty much what they had been accused of doing. And that in any event, the judge was (generally speaking) making a reasonable assesment as to my client's guilt or innocense. The fact that the prosecution's case has holes in it doesn't necessarily mean that the Defendants were innocent or uninvolved in the murder. But feel free to explain why you think my question is tangential or irrelevant and I will be happy to consider it. Also, you might ask yourself if you are angry at me over our previous exchange and whether this anger is coloring your judgment.
I will wait and see if anyone else finds my objection to your rhetoric hard to understand.
Suit yourself. In essence, I am pointing out that there are other possibilities besides the 2 scenarios described by captcorajus. If you feel that my observation is so obviously tangential or irrelevant that no explanation is required beyond simply stating that it is tangential or irrelevant, then so be it. People can draw whatever inference they wish. My inference is that you have no good explanation for your claim, but of course I am starting from the belief that my observation was relevant. (Otherwise I would not have made it.) If someone else sees things differently, perhaps they can shed some light on the issue.
So, you're suggesting that Knox and Sollecito are guilty, but for reasons other than the prosecution's argument. The other commenters here have been discussing the issue, so maybe if you have other arguments, or can point us to another source, that would be relevant. If you're just saying, "But captcorajus might be wrong," that doesn't strike me as being terribly useful, without any further insight to explain why. Or, are you saying the fact that Knox and Sollecito were in a courtroom as defendants is enough to conclude that they're guilty?
"So, you're suggesting that Knox and Sollecito are guilty, but for reasons other than the prosecution's argument." Not exactly. I'm saying that there is good reason to be skeptical of the prosecution's scenario. Nevertheless, the evidence is sufficient to be reasonably confident that Knox and Sollecito were involved in the murder. "If you're just saying, 'But captcorajus might be wrong,' that doesn't strike me as being terribly useful, without any further insight to explain why." I'm saying, in essence, that captocorajus' argument rests on a false dilemma. Implicitly he is asking us to choose between 2 possibilities when in reality there are other possibilities. "Or, are you saying the fact that Knox and Sollecito were in a courtroom as defendants is enough to conclude that they're guilty?" No, I'm not saying that. I'm saying that holes in the prosecution's case do not necessarily imply innocence on the part of the defendants. (As a practical matter, without knowing more, the fact that somebody is a defendant is indeed good evidence they are guilty. But here we do know more so I have not been relying on the mere fact of prosecution.)
Might I interject here boys. My two options for the scenario were based on what the tangible evidence in the case indicates. There is certainly a 3rd possibly that people other than Sollecito and Knox are involved, BUT no evidence has been presented to indicate this so I didn't mention it. Rudy Guede's involvement is about as certain as one can get without direct observation. His bloody handprind, his feces in the toilet and his DNA inside the victim All tangible, all verifiable by second parties. No such tangible evidence exists for Sollecito or Knox. If they were there something of their presence MUST be there. Innuendo, and behavioral analysis without corroborative evidence is not evidence of murder. Rudy Guede can't even be connected to Sollecito and Knox. No emails, no phone calls.... nothing. Rudy Guede is connected to the flat though through downstairs male roommates who testified at his trial that during one visit he fell asleep on their toilet. This case, and the fever that surrounded in regards to Knox borders on misogyny. For Knox, the only bright side is they no longer burn witches in Italy.
"Might I interject here boys. My two options for the scenario were based on what the tangible evidence in the case indicates. There is certainly a 3rd possibly that people other than Sollecito and Knox are involved, BUT no evidence has been presented to indicate this so I didn't mention it." There are many other possibilities (besides your two scenarios) which are consistent with the evidence and consistent with Knox and Sollecito having been involved in the murder. "Innuendo, and behavioral analysis without corroborative evidence is not evidence of murder." Are you saying there is no circumstantial evidence which suggests involvement of Knox and Sollecito?
No. The claim is that this evidence is weaker than the evidence against Guede by a factor of millions, and therefore deserves essentially zero brain time. See the "Epistemic Ruthlessness" section of the post, and the wiki entry "Amount of Evidence".
5Eliezer Yudkowsky14y
No, the evidence is weaker than it would need to be to overcome the prior improbability of "a rape known to have been committed by a random burglar in a flat was a product of conspiracy with a woman who lived there", plus the absence of Knox DNA is very strong evidence against her presence. The degree of the evidence against Guede has nothing to do with the bar - the bar is set by the prior improbability, not by the strength of evidence that Guede happened to leave behind himself.
It seems to me that (1) Guede murdered Kircher; and (2) Knox and Sollecito were involved in the murder, are not mutually exclusive hypotheses. So the fact that there is an extremely strong case against Guede does not necessarily mean that the case against Knox and Sollecito is weak or extremely weak.
Indeed not; if we had 30 bits of anti-Knox evidence, the case against Knox would be strong too. The case against Knox and Sollecito is weak because it is weak, not because the case against Guede is strong.
3Eliezer Yudkowsky14y
That's why I keep on saying not to compare the amount of evidence against Guede to the case against Knox. It's not a comparison operation. It doesn't set a bar. It doesn't set a standard. Now, the fact that Guede left a lot of DNA means it's implausible that Knox cleaned up only her DNA and not Guede's, but that's a whole separate issue. And the fact that we know Guede did it means that there's no unexplained murder around for Knox to be convicted of. But under other circumstances, it would be very easy to have a murder that was in fact committed by two people, one of whom left very strong evidence against herself, and one of whom left less strong but still conviction-worthy evidence against herself. It's just not a relative operation.
Okay, I agree that ideal rational agents with unlimited computing resources shouldn't "care" about the relative strength of evidence; all they have to do is perform the appropriate computation, and the result will come out to whatever it should be. But I've already conceded that "follow the strong signal" is a heuristic for human use, in order to get results that, in reality, better approximate what an ideal rational agent would come up with than the methods that are already programmed into us. The situation we're in is the following: we're investigators on a budget, trying to figure out how to allocate our limited resources among various paths through hypothesis space. Let's say there are two particular paths we're considering, and at the entrance to each of them is a loudspeaker with a voice saying "FOLLOW THIS TRAIL". Except that one of the voices is twice as loud as the other. Now, am I completely crazy, or is it not an epistemically reasonable thing to do to do something like allocate twice the investigative resources to following the signal that is twice as strong? How else should we divide it up? I don't think I need to remind you that reality is consistent: if Knox was really involved in a conspiracy with Guede, then the Knox trail will meet up with the Guede trail, in which case we're not losing anything by devoting the lion's share of our resources to starting along the Guede trail rather than the Knox trail. What, if anything, am I missing here?
3Eliezer Yudkowsky14y
The problem is that finding Guede's semen inside Meredith is not evidence against the hypothesis "Guede and Knox murdered Meredith". Guede's already been caught, too. So now the question is whether to devote any of our remaining attention to trying to catch Knox, and the insufficient/disconfirmatory evidence for this fails to surpass the prior implausibility of the conspiracy hypothesis - it has nothing to do with how hard Guede was caught.
Are you sure semen was found? I've read elsewhere this was a manual rape - still leaves DNA inside but not necc. semen.
0Eliezer Yudkowsky14y
Nope, not sure offhand.
Manual rape? I'm not familiar with that term and a meaning fitting those criteria (DNA but not semen) isn't obvious. I can only assume that 'manual' refers to, well, the last part of it. I wouldn't have expected that kind of rape if murder was going to be on the cards and I would also expect semen around somewhere, showing up with luminol. So perhaps something else is meant.
One meaning of 'manual' is 'of or relating to the hands'. I'm guessing that's what's meant here.
I agree with this, except of course that I am reasonably confident Knox and Sollecito were involved in the murder.
And that would be because...? (The fundamental question of rationality: why do you believe what you believe?)
Mainly because (1) there is evidence of alteration/staging; and (2) Knox and Sollecito are still unable to give accounts of the evening (and next morning) which are reasonably coherent and consistent.
How many total bits of evidence against Knox and Sollecito do you think these things are worth?
I'm not sure . . . I'm ignorant of the evaluation of evidence in terms of "bits." Is there some link you can give me?
* * * *
If my math is correct, I would say somewhere between 3 and 4 bits.
I just want to say thanks for your posts, I have found them very interesting. If the trial has been corrupted then one has to ask why the judge(s) involved would collude in such high profile corruption - that in itself seems unlikely unless there is an unsopken intention to reverse the verdict at appeal, having given the US 'a dose of it's own'. But that seems far fetched. Corruption happens for a reason and those reasons are also traceable. Your argument that conviction was secured on the basis of a fanciful explanation but not without reason is persuasive. I too am of the opinion that things went on but I'm not sure that makes A and R as evil as they are portrayed or even guitly of murder. But mainly, your posts are valuable because, without being able to argue the case mathematically, something clearly is wrong with this Bayesian worldview because it is not explaining life, and if Bayesian rationality is the key to 'knowing', as we are led to believe, then I would not be left feeling that many posts that adhere strictly to Bayesian reasoning are somehow missing the point. And I don't think that is because I am an evolutionary throw-back, I think it is because I have a good sense of things not sounding right - I have that feeling with the Knox trial and with this blog. Ciao
or it could be that Knox and Sollicitos' behaviours were so irrational that it is harder to fathom what the evidence means: 1. they both retracted statements 2. Italy's legal system has been praised as well as criticised 3. the footprint on the bath mat paradox 4. the picture on S's blog 5. K's rape story 6. the verdict is for 'involvement' not physical action 7. capacity to be irrational induced by drugs, hormones, a generational obssession with the supernatural, and the perennial boredom of the over-educated bourgeoisie I reckon that whatever happened that night, K/S got so close to the boundary between fanatsy and reality that they couldn't risk admitting whatever folly they had been up to. I think what is on trial is culture. I count at least 8.
Use ">" at the start of a line to quote.
Thanks for the tip.
Please see the response from RNO (for a start). One inference that people may draw is that I am familiar with this kind of game and choose not to play.
"Please see the response from RNO (for a start)." I don't see anything in RNO's response which would offer an explanation for your claim. On the contrary, it appears that RNO simply misunderstood my point and I explained myself a bit further.
Ah, i think i see the problem here. You say that a weak prosecution does not equal an innocent defendant. I think we can all agree on that. You say that there are other explanations for the evidence. Sounds reasonable enough; after all, even if we're sure of something, we're not absolutely sure, not 100% sure. Back in the first "you be the jury" thread, there was a general agreement that Guede was guilty and Knox was innocent. For Knox, as i recall, there were various estimates from 10% to 30% chance of guilt, thus a judgment of "probably innocent / not likely enough to convict". So, i think it's not that nobody is considering any other explanation, rather, they're convinced that this one explanation is correct. Saying, "there might be another explanation" is a good idea as a general point, but that doesn't mean that another explanation is particularly likely. You keep saying "there are other possibilities" but the problem is: what other scenario are you suggesting, and why should we believe it?
I'm not suggesting any particular scenario. There simply isn't enough evidence to make a good guess at what happened in the hour or two leading up to Kircher's death. It's a bit like the Annie Le case in New Haven. It's reasonably clear who the killer was, but it's not clear why he did it. In any murder case, there is a lot of pressure on the prosecutor to put together a scenario as to how and why the killing happened. And usually it's not too hard to do. i.e. to paint the defendant as a jealous ex-husband; a robber; a competing drug dealer; etc. But I'm not the prosecutor so there's no need for me to put together any scenario. I'm reasonably confident that Knox and Sollecito were involved in the murder, but I do not know what their role was or why they did it.

Excellent post. I don't think I'm ready to wield those sharp implements with quite so much flourish yet; the chance of lopping off my own limbs is currently too high.

However, there are some specific parts of your post I disagree with.

You have to shut that voice out. Ruthlessly. Because it has no way of knowing. That voice is designed to assess the motivations of members of an ancestral hunter-gather band. At best, it may have the ability to distinguish the correct murderer from between 2 and 100 possibilities -- 6 or 7 bits of inferential power on the ab

... (read more)
Low copy number Test... you left out that there are very few labs certified as being acceptable to do that test which is still regarded as experimental and in the UK there is a stringent set of minimum standards for equipment, procedures for the lab itself not to mention the person doing the test. Would you be surprised to hear that the lab that did the test did not meet these requirements in the slightest? It may also be true that though equipped for standard DNA tests was not technically certified at the time even for that? An expert who is convinced the results are reliable when she had never done this type of test before using equipment not designed or set up for such extreme amplification plus leaving out the other calibration tests and tests on a control and not releasing a lot of other details of what she did. She is an employee of the Italian Government just like the prosecutor who unlike many other systems also runs or in this case directs the investigation. The results on the Bra clip and the knife blade are not scientifically usable and should never have been accepted as reliable evidence. This is in the realm of pseudo science. these links have all the details The same with pictures and video And New Scientist Magazine has an article about concerns that world experts in DNA testing have. All of this leaves 2 key bits of evidence, the only 2 alleged to link AK or RS to the crime scene... revealed to not be credible evidence at all no matter what the prosecution expert(s) said about it This blog is great... the lead post does a good job of showing that the theory came first before any evidence and all the efforts since then have been aimed at proving the originally baseless theor
Very interesting reports about the LCN analysis performed in this investigation; I hadn't come across those before (FOA doesn't seem to link to them). This diminishes my confidence in those results meaning much of anything significantly. Thanks!
The problem for the trial was the Defense's argument against the DNA on the knife was undermined by Sollecito admitting there may be the victim's blood/dna on the knife because of a dinner at his house that never happened. Although it tested negative for blood, at that point, the critique against the LCN DNA on the knife is almost superfluous. Sollecito made up a reason to excuse evidence that the defense was challenging the proof of.
About LCN DNA... only the UK currently approves that kind of evidence in a trial BUT they have an extremely strict set of standards on how to run those kinds of tests AND require a very expensive specially built and equipped lab. There are very few DNA labs in the entire world that comply. And there are not many properly trained "experts" who are certified to carry it out. I should mention that none of those labs happen to be in Italy and the Italian technician was not trained or certified to do it. Also her boss in the lab worked as a paid consultant for Mignini at times and there is the implication that she was under the gun to come up with results. All her original DNA tests showed no DNA on the knife at all. Only when she circumvented the built-in limits in the equipment and without doing any of the recommended calibration for false positives and running a lot more amplification runs did she finally come up with partial matches in a very statistically noisy result. And even then great care must be taken in interpreting the results which are much more liable to contamination than standard DNA tests. And even at this point the results with her "interpretation" of the results only yields suggestion of Meredith's DNA... not blood. And this is important: If the knife was cleaned with bleach there would be no DNA but blood would still be detectable. And blood was not detected. The test for blood is very sensitive and it is very hard to eliminate all blood traces and yet there was no blood. That implies strongly that whatever DNA was detected was contamination and a weak result open to interpretation. Her DNA test reports as presented to the court are not complete so the entire process she used for all of these key tests is not available for review. Additionally the court did not allow defense DNA experts to testify about the faults in the prosecution's DNA evidence. Italian judges have poor understanding of forensics and tend to accept unquestioningly the results of

Can anyone find statistics that could tell us what is the probability the crime scene at any given murder contains physical evidence sufficient to indicate a suspect? I would expect it to be around .8-.9 but I don't really have any idea. I'm not convinced that that probability is high enough to completely outweigh the probability that AK and RS had something to do with the crime given that

  • they knew the victim

  • are sociable 21 and 24-year-olds (one of them studying abroad) without alibis on a Saturday night

  • the probability that Guede did not act alone (

... (read more)
The phone timing is widely touted as some sort of proof. The postal police actually cannot establish the exact timing that is claimed. there is apparently surveillance camera footage with a time stamp that shows them still en route by car at the time RS made the call. The discrepancy is no more than a few minutes but if this is true it shows either uncertainty or something closer to tweaking facts to discredit RS. I am looking for where I originally saw this as it is actually very important to impeach the police version. And prior to the call to the regular police RS made a call to his sister-in-law who is a policewoman. And the postal police as far as I know did not mention RS making a call after they came... or if they did it conflicts with the video of them driving there.
Thus "non-negligible probability".

How did Less Wrong do by comparison? The average estimated probability of Amanda Knox's guilt was 0.35 (thanks to Yvain for doing the calculation).

Yvain! How could you? What did the probabilities do to deserve that kind of abuse? (I strongly assert that averaging the probabilities is not a good way to combine such estimates.)

3Scott Alexander14y
...and why do you assert that? If you have good reasons, I'd like to see a top level post on the subject, since this is my natural response to a bunch of probability estimates given by different people with the same information who are rational enough that I care what they think.
Not a top level post because I don't think I have the definitive say on the matter, but I made an article in the wiki that illustrates why the mean of the log-odds makes more sense. Unfortunately, the wiki appears to have issues with math right now, so the article has an ugly error message in it. The formula works fine in the Wikipedia sandbox. If anyone knows what is going on or has any other changes, feel free to edit.
Somebody with no information does not so effectively counterbalance ten people who can describe the positions of every atom on the planet. I calculated an example involving 0.99, 0.5, 0.745 and (1-10^20) but then I noticed badger's link beat me to it.
3Paul Crowley14y
What would the right thing look like? Averaging the log-odds ratio?
That's what I would do. If one person is almost certain (say 1/(10^10^10)) then the strength of their view would be represented. Of course if anyone gives an irrationally low or high answer, or puts <=0 or >=1, then it overweights their views/blows up.
I wonder what implications this has for the method of choosing priors I came up with that is "ask everybody in the world what they think the priors should be, normalize the invalid ones, and take the average of all of them".

Am I really suggesting that the estimates of eight jurors -- among whom two professional judges -- who heard the case for a year, along with something like 60% of the Italian public and probably half the Internet (and a significantly larger fraction of the non-American Internet), could be off by a minimum of three orders of magnitude (probably significantly more)? That most other people (including most commenters on my last post) are off by no fewer than two?

Your assertion of such a high probability of guilt does not constitute a claim that most other c... (read more)

Serious nitpicking going on here. The whole point of my post is that from the information provided, one should arrive at probabilities close to what I said. I don't have appreciably more info than many who participated in my survey, and certainly not more than the jury in Perugia.

Serious nitpicking going on here.

Probability theories and the philosophies thereof are of interest to me and there are a lot of intuitive traps that are easy to fall into.

The whole point of my post is that from the information provided, one should arrive at probabilities close to what I said.

If that is what your point was then I actually disagree with it. I am not comfortable giving odds of 1:999 after looking briefly at two biassed webpages and a wikipedia page that you tell me is fluctuating at the whims of editorial bias. I know damn well I'd be wrong more than once if I did something like that 1,000 times.

Don't forget that "the order, manner, and quantity of browsing will be left up to [them]". It would be quite reasonable for someone to decide to read until a certain level of confidence has been reached. Once you are 99% confident that the poor girl is innocent what do you hope to achieve by marinating yourself in more and more evidence (or, for that matter, the lack of it)?

It would be great if I could go all Liam Neeson and say "if you let her go now, that'll be the end of it. I will not look for you, I will not pursue you. But if you don't, I will look... (read more)

How about a Truth Machine ?
Wow. That book is really good. Thanks for linking to it!
You might also like The First Immortal by the same author.
What if I tried putting it this way: people underestimate the (potential) power of applying rationality techniques as compared with gathering more raw information. It is sometimes possible to be extremely confident about a proposition after an hour of Internet research, even when people who have spent a year "gathering evidence" seem to disagree shaprly.
Totally agree, and that's a point that you explained convincingly in your post. Just so long as I don't have to quantise 'extremely confident' as 0.999. Although given an hour and also given that the discussion is now part of 'the Internet', I expect I would break the 0.99 mark at least.
It's not "nitpicking" to calibrate your probabilities correctly. If someone was to answer innocent with probability 0.999, they should be wrong about one time in a thousand. So what evidence was available to achieve such confidence? No DNA, no bloodstains, no phone calls, no suspects fleeing the country, no testimony. Just a couple of websites. People make stuff up on websites all the time. I wouldn't have assigned .999 probability to the hypothesis that there even was a trial if I hadn't heard of it (glancingly) prior to your post. [edit: I'm referring only to responders who, like me, based their answer on a quick read of the links you provided. Of course more evidence was available for those who took the time to follow up on it, and they should have had correspondingly higher confidence. I don't think your answer was wrong based on what you knew, but it would have been horribly wrong based on what we knew.]
It might have been more useful to ask for confidence intervals around probabilities. Maybe that should become the standard around here? That way, I imagine people who did not care so much about the topic/do as much research, would have had a way to indicate the fact.
No! In this context confidence intervals around the probability have no meaning! I do agree that adding extra information about confidence is important for things like this. It's just that this isn't a case for which confidence intervals (approximately) work. It would make more sense if the probability was a property of the universe itself, then you could establish bounds on where the 'true probability' lies (as discussed with komponisto).
Why can't they be confidence intervals around the probability after doing [some amount] more research?
Relevant post: Readiness Heuristics
That you can do.
I feel the same way. I set the probabilities to 25 (not G alone) / 75 (G alone) after half an hour of reading, just because I wanted to have room to be more confident after 2 hours of reading.

these two things constituting so far as I know the entirety of the physical "evidence" against the couple

I'd like to know your reaction to this argument. There is some other evidence against the "lone wolf" theory and pointing more towards Amanda, specifically that Meredith's bra was removed and the scene rearranged after her death (and not by Rudy), the bloody footprints that match Amanda, and the witness placing all three of them together near the house around the time of Meredith's death.

(Edited to fix formatting)

Why not by Guede? There is no evidence of him leaving right away only supposition. He was next seen at 2AM in a Disco. He is a known burglar and his bloody fingerprints are on Meredith's purse and also he had expressed interest in Meredith to other people prior to that night. He was there for money and also for sex if he could get it. It is perfectly consistent with what is know that he could have stayed and carried out his probable 2nd intention... having sex with her... something he could only accomplish after she died. After a clean up of the mess left when a recently deceased person relaxes certain muscles and voids waste which took long enough for blood to dry and certain marks to become fixed on the body. He may have gone to the other toilet during this time. After a while he returned to her the bra strap was cut and her body rearranged to facilitate sex. He wore condoms and left internal DNA traces either from his fingers or from the outer surface of the condom from when he handled it... After that he did a quick clean of himself and the bathroom.... it is interesting that the people who saw him at the disco later stated that he STANK. There are no bloody footprints that match Amanda's. None. No blood found on alleged footprints in the hall therefore not linked to the murder. The shoeprint in the bedroom originally thought to match her shoe size were on cloth that had a crease that made the print appear shorter and it later was found to be consistent with the distinctive shoes that Guede wore. The bloody print on the bathmat has toe and arch characteristics that are again consistent with Guede's and not the others. Besides the original coroner's conclusion was that there was only one attacker. He was fired from the case and replaced by a new coroner who had a new finding more in agreement with Mignini's theory of a group attack.
Does this kind of evidence have anywhere near 30 bits of inferential power? To me, it seems more like on approximately the same order as psychological evidence.
Have you read the counterarguments from "Friends of Amanda"?
I looked at that site but I didn't see specific counterarguments addressing that point.

I'm a little late to this game, but I spent over an hour, maybe two, comparing the information from the two websites. I had known nothing previously about the case.

My answers: 1: 0.05; 2: 0.05; 3: 0.95; 4: 0.65

So, I feel pretty vindicated. This was a great complement to Kaj Sotala's post on Bayesianism. With his post in mind, as I was considering this case, I assigned probabilities to the existence of an orgy gone wrong as against one rape and murder from one person. There is strong Bayesian evidence for Guédé's guilt, but it's exceedingly weak for... (read more)

Thanks for the kind words! Actually, looking back, I now think I could have done better. In particular, I wish I had been more explicit about the central probability-theoretic point: the fact that the evidence against Guede screens off Kercher's death as evidence against Knox and Sollecito. This point was missed by a number of commenters; if you read the discussion you'll find various people saying that the prior probability "should" take into account the fact that a murder occurred in Knox's house. In actuality, of course, it doesn't matter where you start, so long as you eventually incorporate all of the relevant information; but what must be understood is that if you start with probability mass assigned to Knox and Sollecito because of Kercher's death, then you have to take (most of) that probability mass away upon learning of the evidence against Guede. In other words, under this setup, evidence of Guede's guilt becomes evidence of Knox's and Sollecito's innocence -- something which is counterintuitive and very easy to forget (with tragic consequences). This issue of "choosing the prior" and other Bayesian subtleties encountered in these discussions may be worth revisiting at some point.
I think this insight warrants a great amount of emphasis. The fact that Kercher's death is screened off by some factor unrelated to Knox and Sollecito means that the question of whether the given evidence against Knox and Sollecito is sufficient to judge them co-conspirators is equivalent to the question of whether the given evidence against them would have been sufficient to judge them murder-conspirators in the absence of a body. And I don't think anyone believes THAT is the case.

On the "liar" issue, and the implication of Lumumba:

What numerous people (not here, for the most part, but with some exceptions) have been either forgetting or ignoring, almost to the point of obstinacy, is that Knox did not come up with Lumumba's name spontaneously. She and Lumumba had exchanged text messages on the night of the killing; in one of them, Amanda wrote "see you later". Her interrogators questioned her aggressively about this correspondence, clearly with the implication that Lumumba (as well as Amanda herself) might have b... (read more)

"Knox's "accusation" of Lumumba amounted to no more than saying "Well, all right, I guess maybe he could have done it."" I don't want to cause you to rehash arguments you've had here already. There are so many other pieces of evidence of equal value as her 'lie'. I am aware of the circumstances under which Lumumba was mentioned. At the moment all we can say about the circumstances are that she says she was slapped twice on the back of the head and shouted at, they say they didn't. Perhaps evidence will be produced by one side or another at the slander hearing. It's clear though that she, or possibly her family, has been less than truthful about the length of time she was interrogated for. As for her statement about Lumumba. She said it in her interview ending at 1:45, she repeated it in her statement finishing at 5:45, she repeated it in the "gift" she wrote the following day. Admittedly it is all couched in the "half remembered dream" language of hers. "To "lie" is to make an assertion that one knows to be false" True. I think she is lying. I find it very difficult to believe that in hour ever much of the hour and fourty five minutes of questioning remained after they got onto the text message she became so confused that for two weeks until Lumumba's alibi came good she was unsure whether what she had said about having been there and listened to Meredith's screams was a dream or a half remembered truth. "It does not constitute a positive assertion about the state of the world, and thus cannot be a "lie"." Philosophically I agree with you. I just don't think it was sensible of her to make, and then repeat, statements to the police that one has to defend on the grounds that they are do not consitute positive assertions. "Now, definitions don't matter, of course; but the point is that the lack of correspondence between this particular account and the actual reality of the situation is not Bayesian evidence of her having wished to deceive police about her state of

Rudy Guédé's won his appeal. His sentence has been reduced to 16 years -- ten less than Knox and nine less than Sollecito.

Funny world.

I have no opinion on the guilt or innocence of Knox or Sollecito. I've read the biased accounts of the evidence with amazement. I assumed Guédé's guilt was obvious. Kinda speechless over this new twist. While I can imagine someone thinking all parties were equally guilty, I am unable to find any rationale for deeming Guédé less guilty.

Rudy chose the "fast track" option, which allows for a one third reduction in prison term, and so that's why his sentence was reduced. I don't really understand their system enough to criticize it, but it seems to me that guilty criminals generally would choose the "fast track" option, and get reduced sentences, whereas the innocent generally would choose the full trial, and get full sentences.

The error here is even asking a question about Amanda's motivations when you >haven't established an evidentiary (and that means physical) trail leading from >Meredith's body to Amanda's brain.

Indeed, that's counterintuitive. I believe it to be counterintuitive because it is incorrect. Amanda Knox was a roommate of Meredith Knox's; the initial likelihood of her being responsible is raised by that fact alone. It is normal for police to question motives of people close to the decedent, and it is good practice.

Suppose Hubby ends up shot a few dozen t... (read more)

micio quoted: "while Knox's defenders have no trouble complaining that jurors judged her unfairly based on her behavior in the days after the murder (purchasing sexy lingerie, frolicking around town and making out with her boyfriend), they don't mind pointing out her gentle appearance - or arguing that she has a reputation for being "sweet and generous and kind" etc. In other words - they're fine with exploiting Knox's image only to the extent it lines up with the idea that she's "not the type" who could kill another human being in connection with an act of sexual violence" ---------------------------------------- After a while people will be accountable for the evidence they choose to acknowledge or not. Things like this are inconsequential and incidental. Stick to the evidence. Talk about that. You will be voting for civilization and the rule of law or rule by thugs. What I am finding is that a few people who are commenting here are consistently making the mistake that komponisto described. They are not leaving their perceptual fallacies. For instance this statement: "Amanda Knox was a roommate of Meredith Knox's; the initial likelihood of her being responsible is raised by that fact alone. It is normal for police to question motives of people close to the decedent, and it is good practice." First of all, if the roommate question is enough to bring her in for questioning, then it should be on the same level as the inquiry toward the other two roommates, and this also puts Raffaele further out on the proximity scale. But these checks should be quick and cleared by the lack of physical evidence. And this statement: "Wife...confesses to giving $3,000 in cash she had squirreled away to someone (a description, but no name and he's gone) to shoot Hubby... Is the confession noise? We have no physical evidence. That's somewhat dissimilar to your assertion, I understand. Let's take it back a step..." This has been checked as well. Given the lack of physical evide
Use a '>' at the start of a paragraph that is a quotation
After a while people will be accountable for the evidence they choose to acknowledge or not. Things like this are inconsequential and incidental. Stick to the evidence. Talk about that. You will be voting for civilization and the rule of law or rule by thugs. What I am finding is that a few people who are commenting here are consistently making the mistake that komponisto described. They are not leaving their perceptual fallacies. For instance this statement: "Amanda Knox was a roommate of Meredith Knox's; the initial likelihood of her being responsible is raised by that fact alone. It is normal for police to question motives of people close to the decedent, and it is good practice." First of all, if the roommate question is enough to bring in for questioning, then it should be on the same level as the inquiry toward the other two roommates, and this also puts Raffaele further out on the proximity scale. But these checks should be quick and cleared by the lack of physical evidence. And this statement: "Is the confession noise? We have no physical evidence. That's somewhat dissimilar to your assertion, I understand. Let's take it back a step..." This has been checked as well. Given the lack of physical evidence, then evidence of conspiracy or collusion gets checked. There was no evidence of this either. And the following statement: "...but the behavior is evidence." Not when there is no evidence of conspiracy, collusion, or physical evidence because then you are going back to the mistakes described by komponisto in the post.

These are the concerns as delineated. From the above linked blog.

"The case for appeal is complex and rests on several very firm claims of prosecutorial misconduct:

1.The defense was denied the opportunity to present its own DNA experts;

2.A neurologist acting as witness for the defense testified that Knox could have been subjected to such intense stress, between the horror of the killing and police intimidation that she falsely remembered details that initia... (read more)

I haven't deeply read or studied the whole case itself — but by all means this is a beautiful, detailed, clearly written exposition of your train of thoughts. Thank you.

And yes, the mental suffering of spending two decades in jail + being despised by everyone around when you're actually innocent shouldn't be easy to face even with the highest possible dose of stoicism one could inject herself.

Post now revised in light of comments.

I posted this in response to the Hacker News thread but i wanted to cross-post it here. I appologise for not having read all the comments here first before responding. It seems your post is largely misrepresenting the facts of the case. Have you read the judge's summary? A few key points in the prosecutions case: * 4 mixed DNA samples of the Knox and Kercher. Bloody footprints that match. Blood on the tap put Knox at the crime scene that evening or in the early morning. * A bloody bra in the washing machine * Attempts to frame an innocent man for the crime. * Repeated lying to authorities regarding her whereabouts. Still no fixed alibi. * Knox and Kercher's house was cleaned with bleach. * Sollecito's trainers were cleaned with bleach. A defect in the sole match a blood print on the scene. The decision went through going through 19 expert judges and 6 lay judges. Conviction was unanimous. * Eye witness putting all 3 suspects together outside the cottage that night, and the night previous. * Knox and Sollecito standing outside the crime scene when the police arrived with mop and bucket. Certainly, we can ignore some of the strange behaviour of the convicted (the phone calls, the lies, her past). But the case is much stronger than what this article makes out. It's also worth pointing out that various aspects reported in the media aren't correct - such as the 14-hour interrogation and police violence. Rational thought takes anyone first to the conclusion that there was more than one killer. Guede left the scene soon after the murder (eye witness reports; evidence of cleaning, Guede's own statement). It is clear the crime scene was later returned to, and altered to cover evidence (faked break-in; footprints; removal of bra from the body). With all the additional evidence against Knox and Sollecito, physical and circumstantial, clear motive, and consitantly irration

Hi Nick, While I appreciate that you don't seem to be one of the irrational Knox haters, your comments about the evidence contain a couple of errors, and the one that don't leave out some important facts which cast doubt on almost every single claim.

-Yes, Knox's DNA was founded mingled with Kercher's, but almost all of it was in the bathroom they shared. It would've been almost impossible NOT to find a few instances of their DNA mixed in such a small place, and a place where humans shed copious amounts of hair and skin cells, and even blood (shaving cuts, etc.).

-Not one shred of Knox's DNA was found in Kercher's room. The idea that she somehow managed to remove every microscopic shred of her DNA, while leaving Rudy Guede's behind, is completely implausible. This alone casts enormous doubt on the prosecution's theory. DNA in the bathroom simply proves Knox and Kercher lived together. A total lack of DNA in Kercher's room is compelling evidence she was not at the scene of the crime.

-No traces of bleach were found at the crime scene. Numerous rumors about bleach are clogging message boards all over the internet, including false stories about receipts which showed Knox buying bleach ... (read more)

Jeeze, how did I miss that. Do you have a link? Edit: Also. New people! Welcome.
Sorry, my post contained an error. It was three burglaries in five weeks, not one week. This is from an article at the Daily Mail entitled "Amanda Knox: The Troubling Doubts Over Foxy Knoxy's Role in Meredith Kercher's Murder." Here's the link: And the pertinent text from the article: On September 27, 2007 - five weeks before the killing - Perugia bar tender Cristian Tramantano heard a noise downstairs in his home and found Guede wandering around with a large knife. Tramantano recognised Guede from his work in a nightclub. There was a confrontation between the two, which ended when Guede ran away. On four occasions, Tramantano went to Perugia's central police station to report the break-in, identify Guede as the culprit and to detail how the intruder was armed and threatened him. On each occasion, he says he was ignored and the police refused to log his complaint. The following weekend, there was a break-in at an English-speaking nursery school in Milan in which 2,000 euros and a digital camera were stolen. The school owner, Maria Antoinette Salvadori del Prato, reported it to her local police station. Three weeks later, on Saturday, October 27 - one week before the murder - Mrs Prato arrived at the school early in the morning with a locksmith to replace the front door, only to be confronted by Guede standing in the main entrance. Police were called and Guede questioned. A stolen laptop, digital camera and ten-inch kitchen knife were found in his backpack. But instead of being arrested and charged, Guede was merely escorted to Milan central railway station and placed on a train back to Perugia. In the interim, on the weekend of October 13, there had been a break-in at the office of lawyers Paolo Brocchi and Luigi Palazzoli, in which a firstfloor window was smashed - similar to the break-in at Meredith's house. A computer and othe
The Daily Mail is a British tabloid... frequently posting completely fraudulent information about football players, for example... check your sources friend...
The above quoted story was reported in more than just the Daily Mail. I will look for a few of the other articles.
I read three in the week leading up to the murder, as well. I should recheck that. But it is confirmed that he traveled with a 16 inch knife "for protection" and that he had various run-ins resulting in complaints to police that were ignored by the police.
For the most horrible information about Guede, read his journal. Not fun to read, as it is very dark, but reveals a telling psychological profile as well as shows his time line the night of the murder. His Skype conversation as well gives a lot of information. On the other hand, if you read Raffaele's writing, it shows his innocence.
Yes... a huge fact that did not hit the headlines in any big way.
I'm still waiting on non-tabloid verification. A quick look at the paper's wikipedia page yields a long list of successful libel suits.
Just one more comment. One more article, includes someone who knows Rudy who said he used cocaine.
An interesting article I just found:
Sorry... I'm in the Pacific Time Zone... Just got back to the computer... I am looking into non Daily Mail/Mirror articles. Am at work, so have to look as I can. I do know it was part of the court record and that the kindergarten teacher testified and a police person might have as well. I am looking for something on the court record. Candace Dempsey of the Seattle Post Intelligencer was following that aspect of the case and wrote about it in her blog Italian Woman at the Table. Guede's criminal history is established as fact, as well as the police turning away reports about him.
Thanks for taking your time with your thoughtful and detailed response. I will go through each point in turn below. It's worth mentioning now that I don't actually mean to argue for or against the conviction specifically; rather I feel the prosecution case is significantly stronger than US media has generally reported. Also I'm neither a lawyer, phorensic scientist or logician, so I apologize in advance for any technical mistakes. I'm just trying to assess the information myself that's available on the internet and come to an informed opinion. Certainly some of the evidence appears flawed: the bra clasp, the alleged murder weapon, the eye witness. But we do know that the Judge, and a panel of 19 legal experts, admitted these as evidence. I can't really comment on whether the blood trace on the knife, for example, is sufficient enough to admit the evidence; similarly whether the bra clasp can become contaminated. But the evidence was admitted, and strongly contested, consider and eventually accepted by the panel and the jury. * The DNA evidence: Firstly, I think the important point is that 4 blood samples from the bathroom were found with mixed Knox-Kercher DNA. From " Yes, it does seem that the investigative methods were sloppy and not all samples may be reliable (I acknowledge that there are some problems with the prosecution’s case). But I have yet to read even one article where a reputable DNA expert can explain why sloppy police procedures would result in four separate mixed blood samples". * Also this site (, reporting on the Forensic biologist Patrizia Stefanoni testifying for 9 hours on the stand, notes "But perhaps more damning even than the knife was Stefanoni’s testimony that a mix of Knox’s DNA and Kercher’s blood was found on the floor in the bedroom of a third roommate, Filomena Romanelli [...] her window was broken with a large rock that prosecut
Two more tidbits re: Kokomani (from To give you an example of how absurd it got, Kokomani said that when Amanda was yelling at him, he noticed a wide gap between her front teeth. So the judge asked Amanda to smile, and she did. There is no gap between her front teeth. Nor could Kokomani have had a beer with Amanda and her Italian uncle in July of last year, as he claimed in court, because Amanda was not in Italy at that time and she does not have an Italian uncle.
Hi Nick, Thanks for the response. Regarding the bleach, no evidence was ever presented that anything had been bleached. This story took on a life of it's own after the phony receipts story began circulating. I believe the Judge blocked at least one officer from testifying that he smelled bleach, and was only allowed to say that Sollecito's apartment smelled "clean," because the bleach smell was not listed in the initial report, and was added later, after the false reports about the receipts. Despite the deference True Justice shows for every bit of evidence that favors Knox's guilt, Kokamani's testimony was ludicrous. He claimed that when he saw Knox, Sollecito and Guede together, that Sollecito (a meek computer nerd by all acounts), punched him in the face, and that Knox whipped out a 16 inch (!!!) knife, and said "Come here you! I'll show you!" and that he escaped by hurling olives and a cell phone at her. His testimony contradicted his original statement on many key points, and he had been arrested on drug charges before his testimony. Regarding the footprints, my understanding is that two bloody shoe prints were found. One in Kercher's room that matched Rudy Guede, and another on the bath mat in the bathroom, that was a partial. From everything I've read, the partial print in the bathroom is a mess. It's certainly hard to tell anything from the photos. At various points, the prosecution said it was Knox's, then Guede's, then Sollecito's. The defenses expert witness made a strong case that it was Guede's, but I don't think anyone can conclusively prove anything one way or the other because it's only a partial print. The other footprints were revealed by Luminol, but what True Justice leaves out is that every single one (except for the two I mentioned above), tested negative for the presence of blood. If the footprints weren't bloody, they don't really say anything about the crime, especially since Knox and Sollecito admit to being in the house that morning,
You seem to be privy to a lot of information that I'm not, were you at the trial, or otherwise have better knowledge that the sourced information on the internet? Or is it from reading the 100-page Judge's report of the Guede case? I haven't heard before many of the things you've mentioned in your previous post. Also, some of the things seem to contradict what I've quoted above, a lot coming from the translation of Judge's summary. For example: * " I believe the Judge blocked at least one officer from testifying that he smelled bleach" * The specific details of Kokamani's testimony. * Information like " At various points, the prosecution said it was Knox's, then Guede's, then Sollecito's". * The papers on friendsofamandaknox don't give any sources. How do we know the information is good? I'm sure we could level the same criticism to, but many of the details they have linked to outside sources. * That the mixed DNA can easily be explained away, and DNA can be easily contaminated (there are various expert witnesses at the Guede trial who state otherwise) * That the bra clasp contained DNA of 3 other people. * "it doesn't appear there is any glass on top of the clothes", this contradicts what I've read from the Judge's report. You then go on to explain how glass could have got on top of the clothes (filomena allowed back in to the room), so I'm not sure which you are stating? * Regarding the Daily Mail story - as other posters have mentioned, the Daily Mail certainly isn't a reliable news source, unfortunately. And in general, even a well respected media source alone probably isn't good enough as a source, given how misreported the case has been (like the bleach receipt, the 14-hour interrogation, etc) So again, I'm still not sure the summary of the Judge's document on the Guede case should be considered reliable, do you doubt some of the points? I'm using this to base a lot of my reasoning. If it is an accurate summary
I'm with Nick -- there are very few primary sources available in English, and none of the stuff people are linking to, even the articles in mainstream media, seems like a completely reliable source to me -- especially on all these he said/she said issues of what evidence was actually adduced in court and if so whether it was effectively refuted.
What information do these new priors reflect? Obviously 1-10% of upper-middle class female college students with no history of criminal activity won't commit murder over the next 12 months so I assume that these priors are taking something else into account- like the fact that she lived with a murder victim. But can you say what else you've included? (Or point me if you already have somewhere).
What's going on here is that I'm still trying to figure out how I want to revise that sentence. I may just go ahead and cross it out, since I think the whole issue of "what the prior should be" is a distraction. EDIT: Done.

For those interested, Netflix has a new documentary out about the case:

Dear fellow-poster Desrtopa --

Something called a "karma problem" has prevented me from replying directly to your comment at 03 February 2014 08:52:06AM. In the hope you will spot it, my reply will be posted here. I'm afraid it's the last comment I'll have time for; your reply to it, should you choose to post one, will be the last word in our exchange.

Suppose that you were living in a rather more paranoid country, where the government suspected you of subversive activities. So, they took a current captive suspect, tortured them, and told them

... (read more)

Reply to myself:

I hereby withdraw every negative thing I have said about Amanda Knox at this website. In the period since I posted the comment immediately above, I could not drive from my mind a remark my fellow-poster Desrtopa made in a post at 03 February 2014 07:39:06AM. In effect, Desrtopa asked whether I would fault a person for giving changed-stories because of torture; if I wouldn't, why would I fault the person for giving changed-stories under interrogation so harsh that its effect on the person being questioned would be tantamount to that of torture? At the time, I avoided answering Desrtopa's question.

Just a few minutes ago, I read commentary by a "veteran FBI agent" named Steve Moore. The commentary was posted at , which is a page of a website called Injustice in Perugia. Having known really nothing about interrogation before I read Moore's remarks--and having had no sense how a law-enforcement professional would evaluate various types of interrogation--I had no right to remark on Amanda Knox's performance under interrogation in this case. Moore's remarks have persuaded me of what Desrtopa was, in effect, asking... (read more)

Congratulations on changing your mind! You did it exactly right: you realized you lacked knowledge in a certain domain (interrogation, in this case), proceeded to learn something about it, and updated your previous opinions based on the information you received. Less Wrong exists pretty much in order to help people become better at doing exactly that. My hat is off to you, sir.
Thank you, komponisto. Congratulations to you on this fine essay. I think I must have first encountered it in December 2012, when I first learned of Less Wrong and came to see what the site was. Though I didn't do much to absorb the essay at that time, it stayed in my mind; the news the other day about Knox's re-conviction moved me to read it again. My mental process in response to that rereading has, in a sense, been recorded here, in my last few days' worth of exchanges with Less Wrong posters. When I posted my first comment in response to the essay, I wasn't sure it would be noticed, because the essay was more than four years old. Fortunately for me, Less Wrong's participants were paying attention.

Enter a comment here

Komponisto I have read your account and interpretations of the evidence, and am refreshed and somewhat relieved to finally find some sense of perspective regarding the events. I was troubled by the outcome of the trial, in my mind the events as they were presented simply did not correlate together. When events are correctly modelled, all additional evidence reinforces the hypothesis. Your Bayesian analysis brought a perspective to the likelihood of the various evidence aspects. The prosecutors presentation of the facts was full of i... (read more)

Worse, there was no physical evidence of a forced sexual orgy, there was no evidence that Knox or Sollecito were interested in such an orgy, there wasn't even any evidence that they had the slightest inclination toward that kind of behavior. In other words, it was a hypothesis drawn from nothing, created in order to support a larger hypothesis that was based on extremely weak evidence and made before a far more likely guilty party was known. The massive amounts of evidence pointing to Guide should have made this possibility extremely unlikely, and without it there was absolutely no reason for Knox and Sollecito to be involved at all.

A fascinating look at Roman law versus Germanic:
"Italian Law and You - Welcome to the Jungle!" by Amanda Sorensen

By far the most important evidence in a murder investigation will therefore be the evidence that is the closest to the crime itself -- evidence on and around the victim, as well as details stored in the brains of people who were present during the act.

the evidence against Guédé is such that the hypothesis of her guilt is superfluous -- not needed -- in explaining the death of Meredith Kercher

I think you’re begging the question here. Those who are convinced that K&S are guilty seem to believe that the evidence from the crime scene itself suggests tha... (read more)

"little effort was taken to remove evidence against Guede himself, even very obvious things like flushing the toilet." The assumption here is that Knox and Sollecito carefully removed their DNA, but did not remove Guede's. Isn't the more rational explanation for all of the evidence against Guede, and the lack of evidence against K&S, that Guede did it and K&S weren't even there, as they have always claimed, and as Guede claimed no less than 5 times? Further, there's a lot of supposition about a "clean-up" floating around on the web, but no evidence of one. There's lot of talk about bleach, bleach receipts, bleach on the knife, etc., but no evidence was introduced to support any of these claims. Another claim is no prints were found for Knox, therefore she must've wiped them down. This presumes, incorrectly as it turns out, that no unusable prints were found. In fact, lots of smeared, smudge, or partial prints were found. The prosecution's own expert witness on fingerprints, Giuseppe Privateri, testified he saw no sign of the place being wiped down for prints. There were lots of prints, just not a lot of usable ones, which is totally normal since the way we use our hands often causes the oils left behind to be smeared. Also, to believe this theory of a clean-up, one has to believe that with Superman-like enhanced vision, Knox and Sollecito could see their fingerprints and DNA, and Guede's, and could selectively remove their without disturbing his. This seems far-fetched in the extreme. In the bathroom, some of Kercher's blood was found mixed with Knox's DNA, probably from splashing onto a hair follicles or dead skin cell from Knox. Why didn't this happen in Kercher's room, where the orgy took place? No intermingling of sweat, saliva, or other bodily fluids- in an orgy?!?! It boggles the mind. Last, a lamp from Knox's room, her only source of light, was found on the floor in Kercher's room, possibly put there by Guede as he tried to look for his possessions, or
The idea of a staged break in is unsubstantiated. There is a broken window. Mignini added the interpretation without evidence of such a thing. The two shards on top of the bed turned out to be polka dots on a piece of clothing.
One thing to remember is that Mignini fired the coroner doing autopsy investigation when that person said it was the injuries of a single perpetrator. He then hired someone who said it was more than one perpetrator. If you would like, I can find a link to back it up. So the original report said one person caused the injuries.
3Eliezer Yudkowsky14y
Huh. I wondered if something like this might be the case, but then wondered if I was being selectively skeptical of the prosecution and trying to dismiss all of their evidence. Next time I'll remember to (a) trust myself a little more, and (b) remember that reality itself is consistent rather than fair, i.e., Knox obviously didn't do it, thus if the coroner says it's more than one perpetrator, I should (b1) construct a model in which the coroner is pressured (or fired and redealt) and (b2) penalize the probability of that model because (hopefully) most coroners aren't pressured.
I'm not sure how much hope fits into the Bayesian analysis. My impression is that doing things like pressuring coroners is routine in the US and probably in Italy as well. Of course, pressuring coroners is a special case of "doing things like pressuring coroners" and thus unlikely a-priori, but its not very unlikely a-priori and once the possibility is raised it doesn't call for much penalty.
The significant factor though is not that the coroner was fired and replaced by someone who would report multiple perpetrators. The significant factor is that the original, unprompted, unbiased, objective analysis was that it was a single perpetrator.
Anna, I'd be curious to see the link on this when you get a chance.
If you type "Mignini fired coroner" into Google, a list of articles comes up. There were too many from which to choose. Additionally, a great specific, scientific explanation and analysis on the LCN DNA gathering and testing can be found at ScienceSpheres by Mark Waterbury. He starts the blog that way. He has a PhD in materials science.
I tried a Google search -- I get a few mentions of Mignini firing his coroner, but they either don't mention a reason or they say it was punishment for leaks to the press. None seem to be from impartial sources, i.e. one is from that truejustice site, another is an article in the Stranger (seattle weekly) by a friend of Amanda's ...the closest thing to a real news site was a Vanity Fair article, and like the others it doesn't mention the first coroner saying there was one assailant. This is the problem I mentioned in another comment -- all of our info is second- or third-hand. I'm surprised at how comfortable people are citing this stuff. If this was a comparably public case in the US, there's a good chance the entire reports from both the old and new coroner would be on the Smoking Gun and we could be linking to them directly...
It was part of the trial, however, which is why people cite it.
Again, can you give us your source for this? I'm not doubting you, I just want to get an idea of where it comes from.
The following is from a recap of the defense's arguments on closing day. The recap was written by Kelly Brodbeck who was summarizing Ghirga's arguments. I think he got the rundown from a person present at the trial. This is the first thing I can cite. Will continue to look for more. "He talked about how Mignini stated that the position and condition of Meredith showed that there was more than one person involved in the murder, but when the coroner Dr. Lali said that the body did not show that more than one person was involved, Mignini fired him and replaced him with someone who agreed with his assertions. He said “I wonder why he was really fired??” "
The lack of DNA evidence of a additional perpetrators corroborates the single suspect coroner's result.
No problem... I think even Mignini doesn't dispute it. But I'll seek it out.
A bizarre or unexpected condition of the crime scene is not the explanandum here; Meredith's death is. One person is entirely sufficient to have killed Meredith, and the DNA evidence establishes with virtual certainty that Guede had the kind of contact with her necessary to accomplish this. Unless the evidence suggesting someone else was involved is of comparable power to the DNA evidence against Guede (something on the order of 30 bits), then (and this is the part people have trouble understanding) even paying attention to it at all is automatically hypothesis-privileging. (EDIT: Eliezer corrects below. What I actually wanted to argue here was that, given the certainty of Guede's involvement, the lack of connection between him and Knox or Sollecito is strong evidence against their involvement -- probably enough on its own to outweigh the comparatively weak evidence against them provided by the alleged indications of multiple attackers at the crime scene.) Yes, we might be curious about the unusual mechanics of the crime scene given only one person, but unless they are so strange that assuming someone else's guilt of murder (when we already have a suspect) would constitute a reasonable explanation for them, we have to regard the whole question as a distraction.
6Eliezer Yudkowsky14y
Doesn't follow. You can have a lot of evidence for one true statement and then less evidence for another true statement.
Not sure I understand the objection. The point is that the evidence is extremely weak by comparison; not strong enough to justify any attention.
5Eliezer Yudkowsky14y
Whether evidence is strong enough to justify attention is an absolute threshold. There is no "extremely weak by comparison". There is just "extremely weak".
It is extremely weak on its own, and its weakness is compounded and confirmed by the strength of evidence of someone else. The reason for this is that the strong evidence sets up a perameter, a reference point of what is possible for evidence left behind. It puts lines on the thermeter by which to read the murcury. This is because there is also no evidence of collusion, so the physical evidence has to carry most of the weight, if not all. Otherwise, the prosecution's case operates via a tautology.
Huh? Attention isn't binary, off-or-on; like evidence itself, it's a quantifiable commodity. The stronger the evidence, the more attention. Right?
There will be some threshold of evidence below which a hypothesis ought to receive strictly zero attention. You could probably even formalize this in terms of bounded rationality.
Right, but I don't need to claim that the anti-Knox evidence is below that threshold. Unless, that is, we're talking about extremely imperfect less-than-Bayesian human minds, who can't intuitively perceive the difference in weight that a perfect Bayesian would assign to 30-bit evidence vs. 10-bit evidence.
You're right, this is the part I have trouble understanding. Partly because I have trouble separating the facts of this particular case from the theoretical point you're making. So if you'll humor me for a second: let's say you're the chief of police somewhere, and one of your detectives comes back from a murder scene and tells you "we've arrested a prime suspect and we've got very strong evidence against him, including an ironclad DNA match that ties him to the murder. but we don't think he acted alone, because of X, so we want to keep looking for another suspect." It sounds like for almost any X, your response would be "Don't waste your time. Case closed. Your hypothesis that there was another killer is unnecessary to explain the victim's death." Is that correct? What kind of X would suffice for you to let your detectives keep investigating?
Two examples that come to mind immediately: -Similarly incriminating DNA from someone else in addition to the prime suspect. -Information acquired from the prime suspect himself that points to accomplices.
That's setting the bar pretty high. What about witnesses who claim to have seen two men running from the scene, or heard multiple voices at the time of the murder?
Maybe. But remember that reality is consistent: If two people were at the scene committing the crime, why would there be vastly more evidence of one than the other? Once you have the suspect, you can interrogate him to find out who he knows.
Come to think of it, why would a further (unknown) DNA sample even be enough? You've got an explanation for the crime. Surely there are far more likely priors than a double murder that would explain a second DNA sample, right? "Similarly incriminating" might not really be possible; much of what made the first sample so incriminating is that it matched a guy who you already had reason to suspect. Or did you mean that an unknown DNA sample would not suffice, only one that matched another suspect?
If the victim's body and surroundings contains DNA from two different individuals, that would suggest multiple attackers.
OK, fair enough. I think I understand your standard better now. But let's go back to the actual case. Here's a quote from that truejustice site's summary of the Micheli report: At what point exactly do you part ways with Judge Micheli in that chain of reasoning? To me, his reasoning starts to sound stretched around the middle of the second paragraph. But it sounds like you might have a problem with this logic from the very beginning ...? Are you saying the evidence that the body had been moved is just not worth paying attention to?
If, starting from the premise of Guede's involvement, there are reasons to infer the involvement of someone else, then that sort of thing may very well be worth paying attention to. If the trail through Guede goes utterly cold, however, there comes a point where you just have to declare that Guede's actions + there's-something-we're-missing-about-that-other-"evidence" is a more parsimonious explanation of the data than Guede's actions + someone-like-Amanda-Knox-is-guilty. In this situation, we should suspect that, if we bothered to investigate further, we would find that we were missing something. And sure enough, by golly, that's what often seems to happen.
OK, but why do you keep saying "if"? The judge is making an argument on your terms. He is trying not to privilege the hypothesis. He is starting from the premise of Guede's involvement, and he does find a reason to infer the involvement of someone else. He does not conclude that the trail goes utterly cold, but instead that it leads convincingly to Raffaele and Amanda. Now, you may disagree with this argument, but I still haven't heard the substance of your disagreement. All you've done is gainsay it. Don't get me wrong -- I think your original post was a very good explanation of some huge conceptual problems in the way the case against K&S has come together. If I came in believing they were guilty, you would have raised massive doubts in my mind. And that's no small accomplishment on your part. But it doesn't follow that no case against them remains. In order to convince me, or anyone else who's around the average of 35%, that we should lower our odds to your 1-10% range, I think you have to address the facts more directly. It's not enough to say "there comes a point when you just have to declare..." or that certain DNA evidence "doesn't count." If you were a defense attorney and we were jurors, then you're right, you'd have your acquittal. But it's not a juror's job to distinguish between a 1% and a 35% probability of guilt. To make that case, I don't think you can just point out weaknesses here and there in the prosecution's argument -- you need to lay out the strongest version of the prosecution's case, even if you have to put it together for them, and then show step-by-step why it doesn't lead to a probability higher than 1-10%. I don't blame you for not doing that, because as I've been saying, the primary sources aren't available to do it -- at least not in objective, quality English translations. I'm just not sure how you can get to such low odds without taking a more granular approach. You've suggested that the correct prior is the (very low) odds of som
No he isn't! He's starting from the premise that some investigator found the condition of Meredith's clothing and bloodstains to be unusual given the hypothesis of only one killer. As far as I can tell, he has failed to update properly on the lack of connection between Guede and anyone else who might be a suspect -- not to mention the lack of other evidence (e.g. DNA) that would indicate two or more killers. I'm starting to suspect that we may just have a disagreement about how strong the anti-Knox evidence is. Yes, I agree it isn't literally zero. But that's not the point. The point is that it is utterly dwarfed by the other evidence. Exactly how strong of a dwarfing is this? Well, that's what seems to be the point of contention. I claim the net evidence of Knox's guilt yields a probability of no more than 0.1; you're uncomfortable going below 0.35. The only way to resolve this would be to do some sort of rigorous calculation of the inferential power of clothing-mechanics-analysis evidence -- something which I think would take us too far away from our main topics here. I suppose I can console myself with the fact that it's good news for Amanda and Raffaele (and bad news for the prosecution) if what are probably the most intelligent and sophisticated discussions of their case on the whole Internet consist of vociferous arguments about whether the probability of their guilt should be 0.35, 0.1, or even lower.
That's setting the bar pretty high. What about witnesses who claim to have seen two men running from the scene, or heard multiple voices at the time of the murder?
those would be the witnesses that appeared months later and whose testimony is doubtful. The running feet and scream women's story cannot be true... a reenactment later showed them to be impossible and they were actually not sure if it was Halloween the night before when there would have been a lot more rowdy students around... And the eyewitness was also discredited.
Come to think of it, why would a further (unknown) DNA sample even be enough? You've got an explanation for the crime. Surely there are far more likely priors than a double murder that would explain a second DNA sample, right? "Similarly incriminating" might not really be possible; much of what made the first sample so incriminating is that it matched a guy who you already had reason to suspect. Or did you mean that an unknown DNA sample would not suffice, only one that matched another suspect?
I don't believe there was a staged break-in, but even if there was, how does one logically go from "staged break-in" to Amanda staging it? I detect a logical gap.
I am new to this site. Can someone elucidate for me why the statement above might have been seen as a minus? Just curious. I was asking for the logical link between the condition of the room and Amanda. One hasn't been provided, not even by the prosecution.

And by the way, if one takes your approach of starting from the crime scene and working backwards you must immediately confront the apparent staging of a break-in at the victim's residence. Which, if I recall correctly, was what initially made the Italian authorities suspicious of Amanda Knox.

What exactly do you think makes it "apparently staged"? All the evidence I'm aware of is that it looked like a burglary cause it was a burglary.
To avoid any confusion, can you tell me what you mean by "burglary"? Sorry to be pedantic, but the term apparently means different things to different people. To me, it means breaking into a structure for the purposes of committing a serious crime.
A murder is a serious crime. Guede clearly had to break into the house to commit the murder, so he also committed a burglary by your definition. Which would mean there's no evidence that the burglary was staged, because that would mean that in addition to the burglary that Guede committed, ANOTHER burglary must have been staged by someone else. Which would usually be instantly eliminated by Occam's Razor unless there's a significant amount of evidence of two separate burglaries.
My memory of the case has faded a bit, but as I recall there was evidence suggesting a staged burglary as opposed to a bona fide burglary. Also, Guede needn't have burgled the residence, he may have been invited in by someone who lived there.
You forgot "in a dwelling during the nighttime." ;)
Lol . . . . yes, that's the traditional formulation.

Your point about privileging the hypothesis, and the fact that we feel a need to explain away weird facts in order to believe Knox's innocence, is excellent, though it gets rather buried in a very long post.

As far as the probability estimates go, I expect that many people (like me) did two things: erred on the side of underconfidence, and used numbers as conveying a general feeling. Particularly since it's a criminal case, it doesn't take much to disagree with a conviction. If I'd put the odds of Knox's guilt at .95, I'd say she'd been wrongly convicted, a... (read more)

there's really no reason those numbers should too much higher than they are for a random inhabitant of the city

Actually simply being in the local social network of the victim should increase the probability of involvement by a significant amount. This would of course be based on population, murder rates, and so on. And likely would also depend on estimates of criminology models for the crime in question.

I have heard that the acquittal of Amanda Knox has been overturned. The sources I have found have mentioned the possibility that Knox could be extradited from the US back to Italy and don't rule that out as a possibility. I am hoping someone with an interest in the Knox case (Komponisto) or someone familiar with US laws could tell me whether that is a possibility.

This is relevant to me since simply labeling Italy as a corrupt state that I wouldn't ever visit costs very little (I have no particular reason to visit Italy). However if Knox is (or even could b... (read more)

Briefly, the Italians would have to request extradition. If they did, the US would hold a hearing to determine if there was sufficient evidence to extradite. The standard at that hearing is roughly "Is P(guilty) > .25 ?" Here is a news / opinion article that suggests the Italians are unlikely to ask for extradition, and the standard for extradition probably could not be met. It sounds basically right.
Isn't that a bit of an overreaction? I mean, no matter how bad this miscarriage of justice seems to be, the probability of being wrongly convicted of murder while visiting Italy is low, certainly much lower than the probability of being hit by a car. But being extradited to Italy while visiting the US for a wrong conviction of murder, even if you have never visited Italy before? Probably less likely than being hit by a meteoroid.
I decline to go to Italy based on this and the other research it prompted. The nature of a power structure I am exposing myself to has significance to me even when I am relatively confident in my ability to keep myself self safe. For the same reason I would be unlikely to make a tourist visit a counter-factual USA which still kept all black people enslaved. I'm white so am unlikely to be enslaved but I would still hold what I see in contempt. The information gained about the culture of Italy by the acceptance of ongoing public corruption is not limited to making predictions specific to whether I personally will be falsely convicted of murder.
So you are not going to visit Italy, and possibly the US, as a form of political protest?
That is not what I said. (I am departing this conversation.)
It's a possibility, I think, but it would be a very political issue if it happened, and I would expect the US Department of State to intervene to prevent it.

This post is a year and a half old now, but I think this is still worth saying:

"But come on," says a voice in your head. "Does this really sound like the behavior of an innocent person?"

You have to shut that voice out. Ruthlessly. Because it has no way of knowing. That voice is designed to assess the motivations of members of an ancestral hunter-gather band. At best, it may have the ability to distinguish the correct murderer from between 2 and 100 possibilities -- 6 or 7 bits of inferential power on the absolute best of days. That ma

... (read more)

This type of thing has no place on Less Wrong. You're telling us to ignore an intuition—not just to be skeptical of it, but to ignore it—because of what is, at best, an educated guess about how we evolved.

This is not correct. I'm not telling you to ignore it; I'm telling you that it's worth no more than a few bits of evidence -- few enough to be swamped into unnoticeability by the other data in this context. And, as far as I know, the idea that we evolved in small bands has more than enough scientific support to be taken as a given.

"This type of thing has no place on Less Wrong" is far too harsh, even if you disagree. (It reminds me of "entirely wrong".) Do you have any important disagreement with me about the relative strengths of the evidence under discussion here?

Well, would you agree that the phrase "shut that voice out, ruthlessly" could plausibly be interpreted as meaning "ignore that intuition entirely"? That was how I first interpreted it. Perhaps your post should be rephrased, so it's more clear that "shut that voice out, ruthlessly" actually means "recognize that that intuition is contradicted and outweighed by the other evidence". If that is what you meant, then I agree with this part of your assessment. Well, I do believe that we should not advise people to ignore their intuitions outright, unless we have a very strong argument for doing so. Naturally, this is irrelevant if you are not advising people to ignore their intuitions outright.
Part of it appears to be Komponisto's style: the post is peppered with things like "completely", "utterly" "nothing", "ruthlessly", "gigantic". However, I think "shut that voice out, ruthlessly" may be pretty good advice at least at some point in the thinking/decision process. Because even after you've taken everything (including that voice) into account, and concluded that the true answer is different than it "feels", and the intuition you feel is the result of an identified bias, your right answer might still "feel" wrong. The bias will keep injecting doubt, and it takes effort to shake it off. It's hard to get a heuristic to admit it when it's leading you astray. ;)
Tabooing "ignore", I do not think "that intuition constitutes literally zero Bayesian evidence of guilt" is a reasonable interpretation of my phrase. "Your analysis of this case should be for all practical purposes the same as it would be if you didn't have that intuition" is more accurate (where "practical purposes" include things like deciding whether to regard Knox and Sollecito as "innocent" or "guilty", and how strong a level of rhetoric to permit oneself in expressing one's conclusion). I think it is clear that this post is not about how to distinguish between the kind of extremely small differences in confidence levels that would be entailed by correctly factoring that intuition into one's calculation. Remember that the entire context here is a catastrophic failure of epistemic rationality -- with horrible consequences -- that resulted from people paying too much attention to these types of intuitions. They would have done much better to literally ignore it entirely. (If it actually raises the probability of guilt from 0.001 to 0.002, it would have been better for the police or jurors to have ignored it entirely and estimated 0.001 than to have taken it into account and estimated 0.99, as they effectively did, or 0.5+, as many others have done.)

I have a strong preference for the pragmatism of Occam's razor. If William of Occam had been the Knox case prosecutor it would have never come to trial. When supporting negative cultural stereotypes (i.e. promiscuity of American college girls) becomes more important than a rational outcome results like the Knox verdict arise as the judge overlooks evidence to punish the stereotype instead of the defendant.

I had heard about the case casually on the news a few months ago. It was obvious to me that Amanda Knox was innocent. My probability estimate of guilt was around 1%. This makes me one of the few people in reasonably good agreement with Eli's conclusion.

I know almost nothing of the facts of the case.

I only saw a photo of Amanda Knox's face. Girls with cute smiles like that don't brutally murder people. I was horrified to see that among 300 posts on Less Wrong, only two mentioned this, and it was to urge people to ignore the photos. Are they all too PC or so... (read more)

8Eliezer Yudkowsky14y
[citation needed]
Here's a correlation between ugliness and crime: * * * (30 seconds on Google.)
Although "unattractive individuals commit more crime in comparison to average-looking ones, and very attractive individuals commit less crime in comparison to those who are average-looking" is evidence for SforSingularity's claim, his comment is absurd enough to be taken as satire.

It's clearly absurd to say that pretty girls never murder people. But allowing for the normal hyperbole and inexactitude of conversational English, I don't think that's what SforSingularity means, rather, 'pretty girls are one of the demographic least likely to be responsible for a brutal murder'.

This isn't too unreasonable.

  • First off, the number of murders so ascribable are small: females make up half the population and if we limit pretty to the top 5% or so (a reasonable guess at % for 'pretty enough that a guy will actively note and think "pretty!"'), we're already down to less than 2.5% of the population.
  • Second, women in general commit far fewer violent crimes than men. mentions that for juveniles, at one point, the male:female ratio was 22:1. Let's be conservative and put the young adult ratio at 5:1; now we're down to 0.4%.
  • Third, attractiveness is correlated with IQ, and IQ is well-known to correlate with lower crime rates. (see Wikipedia for a few links; IIRC, WP understates the case but I can't be fashed to dig up the stronger correlations). Let's cut another 10% off the rate, down to 0.36%.
  • Fourthly, a
... (read more)
Interesting. When I read "pretty", I thought of a binary division (make guys judge "pretty or not") and I thought it would yield at least 30-40% as pretty. (Possibly much more, but I've a high degree of certainty that at least that much.) Granted that your test is different than mine, what leads you to your 5% estimate, which looks low to me even with your test?
30-40% seems reasonable for Knox's age group (early twenties). Something closer to 5-10% seems reasonable for the entire female population. Keep in mind pretty people are almost certainly more visible than the non-pretty (especially if you have high socio-economic status).
I think 30-40% is unrealistic: something like 20-30% of females in that age group are overweight or obese, leaving 70-80% in an attractive weight bracket; are we really going to call half of those 'pretty'? It may just be my media-biased high standards, but I don't think I'd call half of all thin young women that.
Right... I was a fool to miss that. You're perfectly right of course. Which leads us to the question of what "natural category" to put Knox in. Should it be "a pretty woman out of all women" or "a pretty young woman out of all young women"? Or lots of other options, of course. (We use some category the moment we compare her to women and not to all humans.) But I'm sure this has been discussed, I haven't read all of this subthread...
Here's one exercise: take your highschool yearbook, open one of the dense pages (with dozens of pics on it), and let your eye drift along the columns with no particular intent (this is hard); how many of the girls will actually catch your attention for being attractive and not for having, say, bizarre & outdated hairstyles? For me, it was less than 1 in 10. (One plain forgets about the bottom 50% and between that and 90% is the 'unoffensive' range.) Considering that my highschool was private and that selection effects were already operating, I have to revise the estimate further down; ~5% seemed good & is a nice round number.
For what it's worth, I remember a study on Stanford undergrads with what was essentially speed dating; men suggested their interest in a second date with ~90% of the women they met, and simultaneously their top criterion for that choice was attractiveness. Even granting that they had loose definitions caused by the study, I suspect that under Dan's metric (binary choice) a reasonably large minority might be tagged "pretty." I also didn't get the impression from the photos on the website that anybody in the Knox case was pretty in the sense that you mean it--I think of your criterion as defining "remarkably pretty" rather than "pretty, if I had to choose," and I'd say you're probably right on <5% being remarkably pretty.
That's like saying very few murders are committed by people named Amanda. That's OK, if you're very careful, but you have to, at least, weigh it against the very few murders by people named Rudy. 2-4 are OK, though.
Reference class tennis. Being an attractive female with a (formerly) well-off family is far more important a reference class than being named Amanda; and the corresponding reference class for Rudy would be being an unattractive man who is a poor African immigrant.
Reread your comment. What is the point of your your first bullet point that pretty girls are rare? That tells you nothing, just as the fact that Amandas are rare tells you nothing. Points 2-4 about the relative propensity to murder are relevant. But I'm explicitly talking about point 1 in isolation.
Yes, it does. If there is any sort of inverse quasi-linear relationship between prettiness and propensity to murder, as one would expect, we would expect the reduction in murder rates compared to the average to be the largest at the extremes - that is, for rarely pretty girls we will expect rarely large effects.
That's not how you used it in your post. Seriously, just read your post. What do these numbers mean?
I rather think I did, since I wrote it. It means that we're talking about an extreme part of the population.
My own reading of the bullet points in the post is something like this: 1) Group X is a small fraction of the population. 2) Reason A why group X is disproportionately unlikely to commit murder. 3) Reason B why group X is disproportionately unlikely to commit murder. 4) Reason C why group X is disproportionately unlikely to commit murder. In the great-grandparent comment above you list an additional reason why pretty girls would be disproportionately unlikely to commit murder, but that wasn't clear at least to me from the original post. So, I agree with Douglas_Knight that bullet point 1 seems to serve a different purpose from points 2 through 4.
I think the "My probability estimate of guilt was around 1%" bit is probably pretty spot on (for the reasons you state), and not absurd. I think the "I only saw a photo of Amanda Knox's face. Girls with cute smiles like that don't brutally murder people" and "Perhaps it is confusing to people that the actual killer is probably a scary looking black guy with a sunken brow" bits are absurd-enough-to-be-satire.
Via what mechanism does wholesome appearance and apple-cheekedness correlate with a disinclination to commit murder? For example, does a murderous disposition drain the blood from one's face? Or does having a cute smile prevent people from treating the person in such a way as to engender a murderous disposition from without? I wouldn't be exactly astonished to find a real, strong correlation between looking creepy and being dangerous. But I'd like to know how it works.
Think about it in evolutionary terms. Roughly speaking, taking the action of attempting to kill someone is risky. An attractive female body is pretty much a guaranteed win for the genes concerned, so it's pointless taking risks. [Note: I just made this up, it might be wrong, but definitely look for an evo-psych explanation] This explanation also accounts for the lower violent crime rate amongst women, since women are, from a gene's point of view, a low risk strategy, whereas violence is a risky business: you might win, but then again, you might die. It would also predict, other things equal, lower crime rates amongst physically attractive men.
One of the comments about the photos was mine I believe. I tried to avoid the photos of both Knox and Kercher (though I failed spectacularly). The fact that Knox is pretty and has a cute smile is worth updating on, perhaps. But for me it would be better to be told those facts rather than figure them out by staring at pictures. Millions of years of evolution have made attractive girls my age more bias inducing than just about anything else in my life. For the lonely I imagine the effect is considerably more dramatic. Surely we don't think the men who wrote Knox letters telling her how beautiful they thought she was are seeing things clearly and objectively. And everyone is programmed to have their protection instincts kick in on the sight of a young, baby- like face (this is why the facial expression of fear resembles the face of a baby).
Hello, everyone, my first post, and while I'm not sure it will be seen as entirely rational, here it is anyway :) I don't know if attractive girls of Amanda Knox's age are more bias inducing. I would tend to think that cute faces do make people feel a certain protective, nurturing instinct. I also think, however, that SforSingularity has a point. I haven't seen any evidence to back it up, but I believe it is rare for "cute" girls to commit violent murder without severe provocation. That's not to say it doesn't happen. From personal observation, it seems that people who look agressive are more likely to be agressive. Would this be due to the balance of testosterone / oestrogen in the womb, throughout childhood