As I think more about the actual false conviction rate I think there may be other factors at work reducing it below 1 in 20. Specifically I think the prosecutor's decision on whether to proceed may matter.
For example, suppose the prosecutor uses the same 95% threshold for reasonable doubt to decide whether to go to trial. If the jury saw the facts exactly the same way as the prosecutor (as of course they wish) then a 95% threshold applied by the jury would exactly correlate with the prosecutor and there would still be a false conviction rate of 1 in 20. However, if the jury saw the facts completely independently from the prosecutor, but still used a 95% threshold, they would be statistically independent. An innocent suspect would expect to be wrongly convicted in 5% * 5% of the time. That is 0.25% or 1 in 400. Real situations would have some correlation so the compound probability would be somewhere between 1 in 20 and 1 in 400.
This still seems like a higher false conviction rate than happens in reality. If juries were known to apply a 95% threshold, then I would surmise that prosecutors were applying a higher threshold in their decision to go to trial with a case.
A lot of factors go into the decision as to whether to indict by a DA, and some DA's are corrupt. In Columbia County, the DA will not plea bargain, after securing an indictment. A plea bargain needs to be done before an indictment. In federal court, the conviction rate is incredibly high, because federal judges get mad if a criminal case is brought before them, that is not airtight, and will punish DA's who bring marginal cases down the line. You are right, that the independence factor, reduces the error rate in general though. And juries sometimes do nullification, which I think is appropriate actually. And some DA's are ethical, and know, even if the case is not beyond a reasonable doubt, if they prosecute, they will get a conviction. That happens with alleged cop killers, drug dealers, and child sexual molesters (the latter two are the most common kind of cases in Columbia County - drugs are everywhere, and there seems to be a shocking number of child molesters). An ethical DA will be very careful to not bring such cases that will result in a conviction, but should not so result.
I know the local DA well having interned for him. We discussed these issues at length. Now I will be assessing his cases for six weeks. I suspect to the extent he does not already, he will be bringing well prepared cases. He knows that I am very suspicious of authority, and am the type that tries to level the playing field, to protect the powerless, and will not cut corners. Not when somebody's freedom is at stake. I am acutely aware that even though I have the skill set to avoid being screwed, most do not. That is most sobering to me. And the criminal defense lawyers around here, are not very good, which is also sobering.
