6/04/2007

The tiny rate that people are wrongfully convicted

There is an interesting discussion of compensation to criminals who have been wrongfully incarcerated here. There are multiple interesting points in this discussion, but one of the more interesting is that there have apparently been only 200 cases exonerated through DNA evidence. Given that there are about 2.19 million people in prison just today and that we are talking about cases over many years, this seems to me like an amazingly small number. Off the top of my head I don't how many of these people were in prison for murder or other serious crimes such as rape or robbery, but suppose that in any given year that it is conservatively 400,000. A rate of 20 per year or even 40 per year or even a total of 200 being exonerated seems remarkably tiny. Even the worst possible and obviously wrong number would imply that only .05 percent were wrongfully convicted. The normal saying is that it is better to let 10 guilty men go than wrongfully convict one. Well, in this case the DNA evidence alone shows you would rather let 2000 guilty go rather than wrongfully convict one. I have lots of problems with overly aggressive prosecutors and would have thought that alone would imply that many more cases would be overturned via DNA evidence, but this evidence on exonerations through DNA evidence, despite the publicity that it receives, is pretty meager.

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10 Comments:

Blogger Hyunchback said...

I don't think it's a question of letting the 2000 go. I think it's a question of making the members of the system responsible for doing their job wrong.

Cops and prosecutors who use faked evidence to convict need to face a penalty for abuse of power. Those who deliberately hide exculpatory evidence need to face a penalty for abuse of power.

Under the present system these bad actors live their political lives without being hit with the consequences of abusing their offices. Lawsuits are aimed at the state, the tax payer, not at the individuals who made the decisions.

There is another downside to the cost of wrongful conviction. Convicting the wrong man leaves an experienced criminal at loose and able to commit the same or worse crimes. Again, it is the citizens who are forced to pay the price of the incompetence and/or evil of cops and prosecutors.

If a doctor or nurse acts in bad faith or is incompetent in practice they face a penalty that could ruin them. Cops who lie, torture to get confession or elicit phony testimony from jail house snitches don't lose their jobs or life savings. Prosecutors who use planted evidence, hide exculpatory evidence, leak damaging but false information to the press and who proceed with cases that are built on lies don't lose their jobs or life savings.

A doctor who ruined the life of one in two thousand patients would be considered a terrible doctor. In some locations in our nation a prosecutor who ruins the life of an innocent man is considered mayor or governor.

6/04/2007 10:57 AM  
Blogger David said...

Without knowing more hard stats, I'd say that 1 in 2000 is an astonishingly high number.

DNA testing can only be used to exonerate in cases where:
* DNA evidence was found.
* DNA evidence wasn't destroyed or contaminated post-trial.
* It's financially feasible to do the testing.

I suspect that a very small fraction of cases meet these criteria.

6/04/2007 8:07 PM  
Anonymous Anonymous said...

I think you have the math wrong. How many cases actually have DNA? Shouldn't that be the denominator? I'm not suggesting that the number of wrongful convictions is huge.

I just think the math is different than you portray it to be.

Dan

6/04/2007 8:46 PM  
Anonymous Anonymous said...

John, I usually agree with you and am very fascinated by your research, but I think you have made some mistakes here. Your denominator is wrong, I think. The correct calculation should be (number of people exonerated)/(number of people with a possibility of exoneration). In other words, someone convicted of check fraud could never be exonerated through DNA evidence. Someone in which evidence has been discarded since trial can never be exonerated. In the vast majority of cases, there was never any evidence that could even be subject to DNA testing.

6/04/2007 9:05 PM  
Anonymous Robert said...

I agree with David and the two anon's here, John - I think you're looking at this wrong.

And to look at it another way, Paul over at Gun, Crimes and Videotape http://crimefilenews.blogspot.com/
points out that the murder clearance rate is down to 36%, steadily dropping as technology (DNA evidence) increased.

Putting these two things together hints to me that we may have wrongfully convicted a TON of people. Like Paul points out, in a case today, the "easy" conviction on the "easy" perp disappears because the perp's got receipts, cell phone records and he shows up on ubiquitious security cameras, etc. If those numbers are accurate, it looks like the wrongful conviction rate (for homicide, anyway) could push 50%.

6/06/2007 5:40 AM  
Blogger John Lott said...

OK, you guys are right. I should have used the number of cases where DNA evidence was available as the demoninator. I don't have this, and it is obviously quite a bit smaller than the number that I used. But I did use an extremely conservative number for those in prison, something that is probably half the true number and I also didn't take into account that these exonerated people were exonerated over many years. Possibly the number that I used was a quarter or less of the true number. If you know what the true rate that DNA evidence is available (I would guess that I search of the web would show this), we could compare that to the rate that I used. But even if DNA is only available in an eigth or a sixteenth of the cases, you are still talking about a big ratio.

6/07/2007 11:35 AM  
Anonymous N. Joseph Potts said...

Glad to see John's "retraction" here. I believe the percentage of wrong convictions is MUCH higher than averred in the original post.

And, as several previous commentators have noted, the percentage of exonerations is MUCH higher than 0.05 when the percentage is taken only on cases for which usable DNA-bearing evidence has survived.

I'd be interested in how many cases sought DNA-based exoneration and were instead REconvicted, as it were, by the evidence. These would be few, as when the perp know he was the perp, but failed attempts at DNA-based exoneration will nonetheless have occurred (hey, what's the downside?), and could be counted.

6/09/2007 1:42 PM  
Blogger John Lott said...

Dear Joe:

I could be wrong, but I detect a small amount of irony in your post. The first part of your post just repeats the earlier arguments. If you think that the conservative numbers that I used are accurate and you want to adjust by whatever percent you want, do so. But I guess that the ratio would still be large. I don't condone convicting innocent individuals, but there are trade-offs.

The second part asks a question that is easy to answer and that is very few prisoners apparently ask for their DNA evidence to be reviewed. Indeed, the researchers who have been trying to find innocent individuals incarcerated have lamented that despite their best efforts few prisoners have availed themselves of this opportunity. Even those involved in the project have assumed that this is true because few of those convicted felt the DNA evidence would exonerate them.

6/10/2007 10:53 AM  
Anonymous N. Joseph Potts said...

John -
You seem to have misunderstood my second question. I wondered NOT how many convicts requested DNA reviews (or better, how many as a percentage of those for whose case DNA evidence existed), but how many reviews confirmed the perp's guilt (we hear about the ones where the perp is exonerated).

You also mistook any intention of irony.

6/12/2007 8:29 AM  
Blogger poohbear said...

I have a somewhat off topic question for you Mr. Lott. What do you think are the chances, for a person who is convicted, at getting a job. (ratios)

2/11/2010 4:39 PM  

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