It proves that mistakes have been made, but in the end, no, I don’t think it’s terribly useful evidence for evaluating the rate of wrongful convictions. Why not? There have been 289 post-conviction DNA exonerations in US history, mostly in the last 15 years. That gives a rate of under 20 per year. Suppose 10,000 people a year are incarcerated for the types of crime that DNA exoneration is most likely to be possible for, namely murder and rape (I couldn’t find exact figures, but I suspect the real number is at least this big). Then considering DNA exonerations gives us a lower bound of something like .2% on the error rate of US courts.
That is only useful evidence about the error rate if your prior estimate of the inaccuracy was less than that, and I mean, come on, really? Only one conviction in 500 is a mistake?
DNA exoneration happens when one is innocent and combination of extremely lucky circumstances make retesting of evidence possible. The latter I would be shocked to find at higher than 1:100 chance.
The appellate system itself—of which cases involving new DNA evidence are a tiny fraction—is a much more useful measure.
There are a whole lot more exonerations via the appeals process than those driven by DNA evidence alone. This aught to be obvious, and the 0.2% provided by DNA is an extreme lower bound, not the actual rate of error correction.
Case in point, I found an article describing a study on overturning death penalty convictions, and they found that 7% of convictions were overturned on re-trial, and 75% of sentences were reduced from the death penalty upon re-trial.
One in fourteen sounds a lot more reasonable to me, and again that’s just death penalty cases, for which you’d expect a higher than normal standard for conviction and sentencing.
The standard estimate is about 10% for the system as a whole.
I’m sorry, but I can’t produce any response but bewilderment. You think DNA exonerations don’t give evidence about the accuracy of the system? Really?
It proves that mistakes have been made, but in the end, no, I don’t think it’s terribly useful evidence for evaluating the rate of wrongful convictions. Why not? There have been 289 post-conviction DNA exonerations in US history, mostly in the last 15 years. That gives a rate of under 20 per year. Suppose 10,000 people a year are incarcerated for the types of crime that DNA exoneration is most likely to be possible for, namely murder and rape (I couldn’t find exact figures, but I suspect the real number is at least this big). Then considering DNA exonerations gives us a lower bound of something like .2% on the error rate of US courts.
That is only useful evidence about the error rate if your prior estimate of the inaccuracy was less than that, and I mean, come on, really? Only one conviction in 500 is a mistake?
DNA exoneration happens when one is innocent and combination of extremely lucky circumstances make retesting of evidence possible. The latter I would be shocked to find at higher than 1:100 chance.
The appellate system itself—of which cases involving new DNA evidence are a tiny fraction—is a much more useful measure.
There are a whole lot more exonerations via the appeals process than those driven by DNA evidence alone. This aught to be obvious, and the 0.2% provided by DNA is an extreme lower bound, not the actual rate of error correction.
Case in point, I found an article describing a study on overturning death penalty convictions, and they found that 7% of convictions were overturned on re-trial, and 75% of sentences were reduced from the death penalty upon re-trial.
One in fourteen sounds a lot more reasonable to me, and again that’s just death penalty cases, for which you’d expect a higher than normal standard for conviction and sentencing.
The standard estimate is about 10% for the system as a whole.