New support for old idea: Death penalty deters crime

For the first time in a generation, the question of whether the death penalty deters murders has captured the attention of scholars in law and economics, renewing an intense debate about one of the central justifications for capital punishment.

According to about a dozen recent studies, executions save lives. For each inmate put to death, the studies say, three to 18 murders are prevented.

The effect is most pronounced, according to some studies, in Texas and other states that execute condemned inmates relatively often and relatively quickly.

The studies, performed by economists in the past decade, compare the number of executions in different jurisdictions with homicide rates over time — while trying to eliminate the effects of crime rates, conviction rates and other factors — and say murder rates tend to fall as executions increase. One study looked at 3,054 counties over two decades.

"I personally am opposed to the death penalty," said H. Naci Mocan, a Louisiana State University economist and an author of a study finding that each execution saves five lives. "But my research shows that there is a deterrent effect."

Critics: Studies flawed

The studies have been criticized, mostly by legal scholars who say the theories of economists do not apply to the world of crime and punishment. Critics say the studies are based on faulty premises, insufficient data and flawed methods.

The death penalty "is applied so rarely that the number of homicides it can plausibly have caused or deterred cannot reliably be disentangled from the large year-to-year changes in the homicide rate caused by other factors," John Donohue, a Yale law professor with a doctorate in economics, and Justin Wolfers, a University of Pennsylvania economist, wrote in the Stanford Law Review in 2005. "The existing evidence for deterrence is surprisingly fragile."

Gary Becker, who won the Nobel Prize in economics in 1992, said the current empirical evidence was "certainly not decisive" because "we just don't get enough variation to be confident we have isolated a deterrent effect."

But, Becker added, "the evidence of a variety of types — not simply the quantitative evidence — has been enough to convince me that capital punishment does deter and is worth using for the worst sorts of offenses."

The debate, which gained significant academic attention two years ago, reprises one from the 1970s, when early and since largely discredited studies on the deterrent effect of capital punishment were discussed in the Supreme Court's decision to reinstitute capital punishment in 1976 after a four-year moratorium.

The early studies were inconclusive, Justice Potter Stewart wrote for three justices in the majority in that decision. But he nonetheless concluded that "the death penalty undoubtedly is a significant deterrent."

New court ruling looms

The Supreme Court appears to have imposed another moratorium on executions as it considers how to assess the constitutionality of lethal injections. The decision in that case, expected next year, will be much narrower than the one in 1976, and the new studies probably will not play a direct role in it.

But the studies have started to reshape the debate over capital punishment and to influence prominent legal scholars.

"The evidence on whether it has a significant deterrent effect seems sufficiently plausible that the moral issue becomes a difficult one," said Cass Sunstein, a University of Chicago law professor who has frequently taken liberal positions. "I did shift from being against the death penalty to thinking that if it has a significant deterrent effect, it's probably justified."

Sunstein and Adrian Vermeule, a Harvard law professor, wrote in their Stanford Law Review article that "the recent evidence of a deterrent effect from capital punishment seems impressive, especially in light of its 'apparent power and unanimity,' " quoting a conclusion of a separate overview of the evidence in 2005 by Stanford law professor Robert Weisberg in the Annual Review of Law and Social Science.

"Capital punishment may well save lives," the two professors continued. "Those who object to capital punishment, and who do so in the name of protecting life, must come to terms with the possibility that the failure to inflict capital punishment will fail to protect life."

To many economists, it follows that there will be fewer murders as the likelihood of execution rises.

"I am definitely against the death penalty," said Joanna Shepherd, an Emory law professor with a doctorate in economics who wrote or contributed to several studies. "But I do believe that people respond to incentives."

But not everyone agrees that potential murderers know enough or can think clearly enough to make rational calculations. And the chances of being caught, convicted, sentenced to death and executed are quite remote. Only about one in 300 homicides results in an execution.

"I honestly think it's a distraction," Wolfers said. "The debate here is over whether we kill 60 guys or not. The food-stamps program is much more important."