Monday, December 22, 2008

Evidence, Deterrence, and the Death Penalty

What type of evidence is relevant to the question of whether the death penalty deters? It seems to me that one kind of evidence, statistical comparison of relevantly similar jurisdictions which have, and do not have, the death penalty, is relevant and acceptable. But defenders of the death penalty suggest another type of evidence, the fact that convicted capital criminals, when given a choice in the matter, choose life imprisonment over death, is given as a reason supporting the deterrence claim.

This just strikes me as a bad argument. It seems to me that what a prisoner decides in his jail cell has little to do with what he might choose when he is thinking of committing a murder and thinks he probably will get away with it.

In any event, even if it is evidence, it is not very good evidence compared to statistics.


Layman said...

According to the Associated Press, recent statistical studies have shown that the death penalty saves between three to eighteen lives for every executed convicted murderer.

"[A] series of academic studies over the last half-dozen years that claim to settle a once hotly debated argument — whether the death penalty acts as a deterrent to murder. The analyses say yes. They count between three and 18 lives that would be saved by the execution of each convicted killer.",2933,280215,00.html

And when discussing deterrence, there are two kinds: general and specific. There is no debate that the death penalty is an effective specific deterrent.

Victor Reppert said...

It would be nice to see how the evidence was gathered.

Blue Devil Knight said...

It would be key to see the methods used, not just the output: I don't trust social science, especially popular press summaries of social science.

Dan said...

I'd be interested to know why the range of results is so broad? It seems that a trustworthy (high-correlation, low margin of error) statistical analysis would deliver a more specific result. The difference between 1 execution = 3 lives saved and 1 execution = 18 lives saved is a 1500% "return" per act of execution.

Further, how would one gather "real" data that supports this argument in the first place? Measuring any difference in per-capita homicide rates before and after the implementation of the death penalty would have to factor out a tremendous amount of externalities to isolate the direct correlation. Failure to mention these data tell me that any statistical methods applied were likely highly inferential, subjective and perhaps contrived.

As you no doubt can tell, the story feels manipulated to me. Without the ability to understand and (if needed) contest the specific methods applied, this "statistic" is, ostensibly, meaningless.

Besides, since Dr. Reppert's page is a philosophy blog, it warrants mentioning that there are overarching moral/ethical issues at play here that must also be considered. Even if the statistics are accurate (which I highly doubt), it is not sufficient to then suddenly blurt out that the ends justify the means simply because there is a net "positive" affect on human lives.

Mike Darus said...

What message would it send if capital crimes were downgraded to a maximum of life in prison? Would this signal a social shift to making serious crimes less serious?