One of the most frequently made claims about the death penalty is that it deters potential murderers. That was the claim when the Supreme Court reinstated capital punishment in 1976. It is the claim today after a revival of research about the topic in the last decade.
But a distinguished committee of scholars working for the National Research Council has now reached the striking and convincing conclusion that all of the research about deterrence and the death penalty done in the past generation, including by some first-rank scholars at the most prestigious universities, should be ignored.
The committee found that the research “is not informative about whether capital punishment increases, decreases, or has no effect on homicide rates.” No study looks at what really matters, by comparing the deterrent effects of capital punishment with other penalties, like life without parole. A lot of the research assumes that “potential murderers respond to the objective risk of execution,” but only one in six of the people sentenced to death in the last 35 years have been executed and no study properly took that diminished risk into account.
“Nothing is known about how potential murderers actually perceive their risk of punishment,” said the criminologist Daniel Nagin, chairman of the committee.
The committee was careful to say what it did not examine, including the proven risk that an innocent person could be sentenced to death and the fact that the administration of capital punishment could well be discriminatory.
On Wednesday when Connecticut’s governor, Dannel Malloy, signed the state’s new law abolishing the death penalty, these problems were on his mind. As a former supporter of capital punishment, he said that he “came to believe that doing away with the death penalty was the only way to ensure it would not be unfairly imposed.”
The 33 states that retain the death penalty should follow that lead.