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?

I'm inclined to disagree with your reasoning. The sort of training I described will not significantly improve the toolkit available to the sorts of people who become lawyers, any more than improving grade-school math education will significantly improve the toolkit of accountants. But it might significantly improve the toolkit available to average people, and thus to average jurors, and might thereby change the sorts of arguments that are effective in courtrooms. Ideally, it leads to an arrangement where truth-preserving arguments are more effective than they are now, and therefore get used more, which seems as good an operational definition of using "rational techniques to arrive at correct decisions on guilt" as I expect to get while still keeping randomly selected humans involved. (I more or less endorse the use of randomly selected humans, as a way to avoid regulatory capture, though it's hard to say whether regulatory capture would be worse than the foolishness of juries.)

That said, I mostly agree with your conclusion: it probably wouldn't work, though not for the reason you describe. To keep your martial analogy, I think the result would be similar to that of instituting formal calisthenics programs in grade school in the hopes of improving the quality of our soldiers.

I see. If this critical-thinking curriculum raised the fallacy/bias-spotting abilities of ordinary folks, and did not raise the sophism-spinning abilities of lawyers, then the jurors' abilities would rise relative to the lawyers', which would improve juries' chances of reaching the correct verdict. I think I agree with this.

But why should we assume that lawyes' abilities will not rise as well? You write that this training would not "significantly improve the toolkit available to the sorts of people who become lawyers." But surely lawyers will pla... (read more)