Death penalty a deterrent to murder? Study says evidence unclear

Does facing the death penalty make would-be killers rethink their actions?

The question has long been at the center of arguments for and against the death penalty, but a committee formed by the National Research Council released a report Wednesday saying that previous studies, despite their claims, have not been able to fully answer the question and therefore should not be used in debates over capital punishment.

The United States Supreme Court reinstated the death penalty in 1976. Last week, Connecticut became the 17th state to repeal capital punishment. An Ohio man was executed Wednesday and another man was scheduled to die by lethal injection Friday in Delaware.
The Committee of Deterrence and the Death Penalty concluded that studies on the death penalty and its potential effect on homicide rates -- both pro and con -- contain fundamental flaws that essentially make them moot.

For example, the studies do not include the effects of other forms of punishment -- such as life in prison without possibility of parole, and whether it too acts as a deterrent. The studies, study authors wrote, don’t “consider how the capital and noncapital components of a regime combine in affecting the behavior of potential murderers.”

In other words, previous studies don’t determine whether potential killers think about the possibility of spending their lives in prison or ending up on death row before they commit their crimes.

The lack of comprehensive information makes the research inconclusive, the study authors said. “We recognize this conclusion will be controversial to some, but nobody is well served by unfounded claims about the death penalty,” committee Chairman Daniel Nagin said in a telephone news conference.

“Nothing is known about how potential murderers actually perceive their risk of punishment,” he said.

Nagin, a professor of public policy and statistics at Carnegie Mellon University, said more data were needed on the full range of penalties across the country before they are cited as basis for changing public policy.

More precise data collection is needed, Nagin said, because the issue is so fundamentally difficult to study. For example, it’s scientifically impossible to know exactly what was going on in someone’s head when they killed someone — even if they are interviewed about it afterward.

The study also concludes that data alone can’t reveal what the homicide rate in a state with the death penalty would be if it didn’t have the punishment -- and vice versa.

Digging deeper for data may take a while, said Charles Manski, a professor of economics at Northwestern University who was also involved in the study. “As a nation, we’re used to [taking a long time] for medical research, and I think there’s been a problem in this area of research,” he said.

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