WASHINGTON -- In the more than three decades since the national moratorium on the death penalty was lifted, there is no reliable research to determine whether capital punishment has served as a deterrent, according to a review by the National Research Council.
The review, partially funded by the Justice Department's National Institute of Justice, found that one of the major shortcomings in all previous studies has included "incomplete or implausible" measures of how potential murderers perceive the risk of execution as a possible consequence of their actions.
Another flaw, according to the review, is that previous research never considered the impact of lesser punishments, such as life in prison without the possibility of parole.
"Fundamental flaws in the research we reviewed make it of no use in answering the question of whether the death penalty affects homicide rates," said Carnegie Mellon University professor Daniel Nagin, who chaired the council's study committee.
Nagin said Wednesday that the panel reviewed the work of "dozens" of researchers since a 1976 Supreme Court decision ended a four-year national moratorium on executions.
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"We recognize that this conclusion may be controversial to some," Nagin said, "but no one is well served by unsupportable claims about the effect of the death penalty, regardless of whether the claim is that the death penalty deters homicides, has no effect on homicide rates or actually increases homicides."
The council's review comes exactly a week after the Connecticut Legislature voted to abolish capital punishment for future crimes following a lengthy debate that cited a lack of evidence about deterrence among the reasons for its repeal in favor of life in prison without parole.
"For decades, we have not had a workable death penalty," Democratic Gov. Dannel Malloy said following the vote. "Going forward, we will have a system that allows us to put these people away for life, in living conditions none of us would want to experience. Let's throw away the key and have them spend the rest of their natural lives in jail."
Malloy has pledged to sign the legislation, which will leave 33 states with the death penalty.
Richard Dieter, executive director of the Death Penalty Information Center, which closely tracks capital punishment in the U.S., said deterrence has always been "hard to measure," partly because of the time it often takes for states to carry out executions.
In Connecticut, for example, there are 11 people on death row, but only one person has been executed in the past 52 years.
As a result, Dieter said, the issue of deterrence has faded from the public discussion about capital punishment. It has been overtaken, he said, by such considerations as whether the death penalty remains an appropriate punishment for particularly heinous acts.
"If the death penalty is going to be justified, it has to rest on other grounds," Dieter said.
Isaac Ehrlich, the University of Buffalo's Department of Economics chairman, stands by his research that supports capital punishment as a deterrent to homicide.
"This is not the first time people have raised questions (about the research)," Ehrlich said, rejecting the council's claim that prior research did not account for murderers' considerations of the possible risks.
"A lot of murder is calculated, and people do take into account what might happen to them as a result," he said.
Kevin Johnson writes for USA Today.