[tptacek]

There's a statistical bias in this argument; we remember the cases in which we've learned people were convicted on shoddy evidence, but pay little attention to the overwhelming vast majority of uneventful cases in which justice is (at least nominally) served. I think it's facile to suggest that false convictions are common, and I think it's possible to point that out without arguing that we should be any less vigilant against false convictions.

[binarybits]

There's also a countervailing bias that I suspect is far more important: most wrongly-convicted defendants have no way to prove their innocence, and so we never learn that they were wrongly convicted. Many criminal defendants are not sophisticated about the law, and their cases are handled by overworked public defenders. The courts in many states are extremely stingy about giving defendants access to evidence or legal appeals post-conviction. So even if potentially-exculpatory evidence emerges, the convict often can't do anything with it.

This is one of those statistics that will never be known with any precision, but even if the number of known exonerations is small (which I don't know to be the case) that doesn't prove that the number of innocents in jail is small.

[MikeCapone]

I would think that most mistaken convictions happen to cases that receive very little scrutiny, including by the media (think poor uneducated ethnic minority with state-provided overworked lawyer).

[lambda]

> overwhelming vast majority of uneventful cases in which justice is (at least nominally) served.

You are assuming in that statement that there is an overwhelming majority of cases in which justice is served. You even try to leave yourself an out with the "at least nominally", which demonstrates part of the problem with your argument.

Among the problems with this argument: the assumption that many of the crimes we are convicting people for are actually bad, and thus worthy of being considered crimes. The assumption that convicting and imprisoning people for the crimes that they commit is just, or even that it achieves whatever ends it is supposed to achieve. The assumption that people are convicted of crimes on the basis of whether or not they actually committed the crime, plus a small random factor due to mistakes, rather than systemic social reasons relating to class, race, poverty, and other social issues (even if many of the people who are convicted of crimes are actually guilty, if the guilty of one group are convicted at a far higher rate than the other group, it's not quite right to say that justice is served in this case).

You have to be careful about bias in the other direction; the just world fallacy. It's very easy to believe that we live in a just world (and part of why people find such hope in the idea of just deities); when something bad happens, many people try to find a reason or to justify it. But in fact, we do not live in a just world; we live in an impartial world, populated with imperfect people. Given that, you need to be skeptical of any time you find yourself thinking that the vast majority of any particular situation is just, especially with stakes as high as criminal justice.

[btilly]

I don't have any up to date figures, but http://www.caught.net/innoc.htm suggests that the rate of wrongly convicted innocent people could be around 10%. So the vast majority of convicted people belong there. Indisputably a lot of people walk free who are guilty. But there are also a lot of innocent people behind bars.