Rational Justice

geebee2

I'm interested in how courts and juries might use rational techniques to arrive at correct decisions on guilt.

In a complex case, it would seem to sensible to assess each component of the prosecution and defence case, and estimate the relative likelihood. If the prosecution case is (say) 100 times more likely than the defence case, then you can say the defendant is guilty beyond reasonable doubt.

I never heard of this being done though. I recently made an analysis of the Massei report into the Amanda Knox case. It looked like this ( see http://massei-report-analysis.wikispaces.com/ for the entire analysis and some insight into the numbers below ).

Event	Prosecution Probability	Defence Probability
Phone at cottage at 22:13	1%	99%
DNA evidence correct	50%	50%
Break in staged to look like Rudy did it vs unstaged break-in	10%	90%
Conspiracy among 3 near strangers with no apparent motive vs burglary gone wrong	5%	95%
Murder weapon was two knives rather than one	10%	90%
Time of death 23:30 vs 21:10 according to empty duodenum	10%	90%

This is perhaps a bit vague. It's not a great example, because in the end I didn't find any credible prosecution evidence. It's not entirely clear what the "probability" numbers here actually are, and whether two columns are needed. But hopefully it shows that the Massei's account of the murder is quite improbable, and there is considerable doubt.

I'm interested in possibly devising a more complete framework for how such an assessment should be done, the pitfalls that need to be guarded against (how uncertain are the probability estimates?), and even views as to how "reasonable doubt" should be quantified.

Perhaps readers would like to make an assessment of other interesting cases, to explore the issues.

Or how would you approach this problem?

I'm interested in how courts and juries might use rational techniques to arrive at correct decisions on guilt.

Event	Prosecution Probability	Defence Probability
Phone at cottage at 22:13	1%	99%
DNA evidence correct	50%	50%
Break in staged to look like Rudy did it vs unstaged break-in	10%	90%
Conspiracy among 3 near strangers with no apparent motive vs burglary gone wrong	5%	95%
Murder weapon was two knives rather than one	10%	90%
Time of death 23:30 vs 21:10 according to empty duodenum	10%	90%

Perhaps readers would like to make an assessment of other interesting cases, to explore the issues.

Or how would you approach this problem?

This is an excellent post. I've posted no-Karma articles to my page (can you see them? I haven't been here long...), dealing with some of these ideas. This is the subject I'm most interested in. Keep up the great posting, and feel free to call me. Jake Witmer 312-730-4037 (in and out of good cell locations this month)