Should the U.S. Abolish the Death Penalty?

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There has been a sea change in the scholarly literature on deterrence in recent years. Dr. Paul Rubin of Emory University summarized it in his congressional testimony in 2006. "The literature is easy to summarize: almost all modern studies and all the refereed studies find a significant deterrent effect of capital punishment. Only one study questions these results."

Opponents frequently make the claim that the lower homicide rates in states that do not have capital punishment disprove deterrence. This argument is so obviously invalid that a sophomore social science student could see it. Such simplistic comparisons fail to control for the other ways in which the states vary. We don't have to guess about this; we know. Those same states had lower rates during the moratorium period of the late 1960s to mid 1970s when no executions occurred in the United States.

The studies that properly control for the other variables are the ones referred to in Dr. Rubin's testimony. Although it is not an exact science, and probably never will be, a remarkable number of researchers using different approaches have produced a strong consensus that there is a deterrent effect where the death penalty is genuinely enforced. Estimates vary, but it is likely that somewhere in the range of 5 to 18 innocent lives are saved per execution.

What happens in states where the death penalty is obstructed, such as California and Pennsylvania, is insufficiently researched to draw any firm conclusions, but in any event the correct policy response is to remove the obstruction.

Faced with the modern deterrence studies, opponents usually cite the critical article by Donohue and Wolfers. Unlike the authors of the studies finding deterrence, Donohue and Wolfers chose not to publish their article through the peer-reviewed publication process that is the standard in the field for assuring that research meets at least the basic criteria for validity. Instead, they chose to publish in a law review. Law reviews are edited by law students who typically do not have the education or experience to distinguish valid social science methodology from statistical sleight-of-hand. Why did Donohue and Wolfers bypass the standard review process? Applying the Harry Truman principle, if you see someone avoiding the kitchen, there is a good chance he can't take the heat. Dezhbakhsh and Rubin's response to Donohue and Wolfers is presently in the "working paper" stage and is available on SSRN , abstract 1018533.

It is a basic principle of human behavior that incentives matter. Increase the cost of doing anything, and fewer people do it. When the price of gas goes up, more people take the bus rather than drive. Applying that basic principle, we would expect that a credible, enforced death penalty would reduce the number of homicides, particularly the premeditated homicides that are generally punished by death. (Whether second-degree murder or voluntary manslaughter would be deterred is moot, as these crimes are not capital, and there is no serious proposal they should be.) Those who would claim that murder is somehow different, an exception to this basic principle, would need powerful empirical evidence to support that claim. The evidence is powerful in the other direction.

Using the Emory study estimate, over 18,000 have been saved from murder by the enforcement of capital punishment from 1977 to 2006. Tens of thousands more could have been saved if enforcement had not been obstructed by excessive delay and by overturning judgments based on fabricated restrictions that are not really in the Constitution and have nothing to do with actual guilt of the crime.