I give a history of the 2009 leaked script, discuss internal & external evidence for its authenticity including stylometrics; and then give a simple step-by-step Bayesian analysis of each point. We finish with high confidence in the script's authenticity, discussion of how this analysis was surprisingly enlightening, and what followup work the analysis suggests would be most valuable.
If you're already familiar this particular leaked 2009 live-action script, please write down your current best guess as to how likely it is to be authentic.
This is intended to be easy to understand and essentially beginner-level for Bayes's theorem and fermi estimates, like my other Death Note essay (information theory, crypto) or my console insurance page (efficient markets, positive psychology, expected value).
Be sure to check out the controversial twist ending!
(I'm sorry to post just a link, but I briefly thought about writing it and all the math in the LW edit box and decided that cutting my wrists sounded both quicker and more enjoyable. Unfortunately, there seems to be a math problem in the Google Chrome/Chromium browser where fractions simply don't render, apparently due to not enabling Webkit's MathML code; if fractions don't render for you, well, I know the math works well in my Iceweasel and it seems to work well in other Firefoxes.)