The abstract of the article:
Recent evidence suggests that capital punishment may have a significant deterrent effect, preventing as many as eighteen or more murders for each execution. This evidence greatly unsettles moral objections to the death penalty, because it suggests that a refusal to impose that penalty condemns numerous innocent people to death.Wow. As an opponent to the death penalty, this is about as convincing of evidence I could find to potentially change my mind. My opposition to the death penalty is not rooted in a moral belief that the government should not sponsor killing, but rather in the belief that the government shouldn't be TRUSTED to find out who deserves to be executed. In essence, I don't trust the government with my social security money, so why should I trust them in trying to put people to death. As a result, any evidence that executions represent a clear deterrent to murder means that the morality of the situation (in my eyes at least) is much less obvious. Ultimately, if I were certain that the number of innocent individuals killed (by the government or private citizens) was one less with the death penalty, I would have to think long and hard about whether I would remain opposed to capital punishment.
Capital punishment thus presents a life-life tradeoff, and a serious commitment to the sanctity of human life may well compel, rather than forbid, that form of punishment. Moral objections to the death penalty frequently depend on a distinction between acts and omissions, but that distinction is misleading in this context, because government is a special kind of moral agent.
The familiar problems with capital punishment -– potential error, irreversibility, arbitrariness, and racial skew -– do not argue in favor of abolition, because the world of homicide suffers from those same problems in even more acute form. The widespread failure to appreciate the life-life tradeoffs involved in capital punishment may depend on cognitive processes that fail to treat “statistical lives” with the seriousness that they deserve.
Even more complicated is what clear evidence showing that the death penalty saves lives would mean to rights based groups. After all, the most basic thing any government is responsible for is the safety of its citizens, both from domestic and foreign enemies. If the government were to ignore a clear life-saving benefit because of its own squishy moral qualms with the "morality" of government sponsored killing, I think it would have some explaining to do to its public.
This is all besides the point...for now. I don't think Cass and Adrian have made such an overwhelming empirical argument for the death penalty that it's deterrent benefits are clear. But it's not so difficult to imagine a world where the evidence becomes so substantial that it can no longer be ignored. What will we do then?