Our research was cited in the recent Supreme Court case on capital punishment:

It was just a dissent, but still.

I agree with Breyer that the death penalty has lots of flaws. On the other hand, Justice Antonin Scalia has a point that it it’s hard to call it unconstitutional given that it was explicitly mentioned in the Constitution.

I won’t express any opinion on the constitutional issues. Rather, I’ll approach it from the standpoint of decision analysis. As I wrote in this space a few years ago:

My larger perspective on the death penalty, informed by my research with Jim Liebman several years ago, is that you can only accept capital punishment if you’re willing to have innocent people executed every now and then. And, the more effective you want the death penalty to be, the more innocents you have to execute.

The occasional execution of innocent people might be deemed ok in some settings—-they shoot deserters in wartime, and if a country is in the midst of a big enough crime wave, I could see people accepting the need for the occasional lethal mistake of the judicial process. My point here is just that if you want to execute people on a regular basis, you’re gonna make some mistakes. We saw this in our research on death-sentencing reversals, which were not merely the actions of a few liberal court panels.

As Donoho and Wolfers discussed several years ago, the evidence of the deterrent effect of the death penalty is not clear. This is not to say there is no deterrent effect, just that the evidence is not really there, one way or another. Scalia cites the paper by Dezhbakhsh, Rubin and Shepherd claiming that each execution deters 18 murders but, as I wrote, their story is possible, but it seems to me (basically, for the reasons discussed in the Donohue and Wolfers paper) not a credible extrapolation from the data.

Scalia also cites Cass Sunstein’s 2005 statement, “All in all, the recent evidence of a deterrent effect from capital punishment seems impressive, especially in light of its ‘apparent power and unanimity,'” but not Sunstein’s 2008 retraction, when he wrote, “impossible to disentangle the effects of execution policy from other changes affecting murder rates . . . the best reading of the accumulated data is that they do not establish a deterrent effect of the death penalty.” Not that Sunstein is an authority here, but he did co-write that last piece with Wolfers, who did do research on the topic, and the real point is that if you want to quote Sunstein, you want his latest on the topic.

To Scalia’s credit, though, he (Scalia) does seem to accept that error is part of the process, and that innocent people will be sentenced to death. He just accepts the tradeoff, which is fair enough.

In his concurring opinion, Justice Clarence Thomas wrote, “Whatever one’s views on the permissibility or wisdom of the death penalty, I doubt anyone would disagree that each of these crimes was egregious enough to merit the severest condemnation that society has to offer.” But this misses the point that, if an innocent person is executed, it’s a mistake no matter how bad the crime.

Again, this is not to say that the death penalty is a bad idea, just that, if you want the death penalty, you have to accept the occasional innocent person being executed. That’s a tradeoff we have to face.

P.S. Scalia also characterized the dissenters as “waving over their heads a ream of the most recent abolitionist studies,” so just let me emphasize that our paper is not “abolitionist” — it’s just empirical.