Scientists agree, by an overwhelming majority, that the death penalty has no deterrent effect. They felt the same way over ten years ago, and nothing has changed since then. States without the death penalty continue to have significantly lower murder rates than those that retain capital punishment. And the few recent studies purporting to prove a deterrent effect, though getting heavy play in the media, have failed to impress the larger scientific community, which has exposed them as flawed and inconsistent.

The latest issue of the Journal of Criminal Law and Criminology contains a study by a Sociology professor and a graduate student at the University of Colorado-Boulder (Michael Radelet and Traci Lacock), examining the opinions of leading criminology experts on the deterrence effects of the death penalty.

The results reveal that most experts do not believe that the death penalty or the carrying out of executions serve as deterrents to murder, nor do they believe that existing empirical research supports the deterrence theory. In fact, the authors report that 88.2% of respondents do not think that the death penalty deters murder—a level of consensus comparable to the agreement among scientists regarding global climate change. At the same time, only 9.2% of surveyed experts indicated that they believed the death penalty results in a significant drop in murder cases (56.6% completely disagreed with that statement, while 32.9% thought the correlation between capital punishment and lower homicide numbers to be “largely inaccurate”; 1.3% were uncertain).

The study builds upon previous research, published in 1996, in which the opinions of 67 leading experts in the field of criminology were surveyed. The most recent study sent the same questions to a new group of experts (a total of 73), among whom were fellows from the American Society of Criminology, as well as award-winning criminology scholars.

A majority of respondents also expressed the opinion that death penalty states don’t have lower homicide rates than states where capital punishment has been abolished. The authors point to empirical evidence that backs this up — in 2007 murder rates in states that still had the death penalty exceeded those in states that have abolished it by no less than 42%. More than eighteen percent of surveyed experts went even further and actually expressed the belief that the death penalty leads to a higher rate of murders, something the authors call the ‘brutalization hypothesis.’

In addition, a majority of respondents involved in both the 2008 and the 1996 studies believe that “(d)ebates about the death penalty distract Congress and state legislatures from focusing on real solutions to crime problems.” Overall, the authors conclude that there is no significant difference between the opinions of experts from the 1996 and the 2008 time periods and that “a vast majority of the world’s top criminologists believe that the empirical research has revealed the deterrence hypothesis for a myth.”

Radelet and Lacock also discuss and point to significant inconsistencies in a number of studies conducted by economists, who have found the death penalty to have a deterrent effect. These inconsistencies lead them to conclude that “(r)ecent econometric studies, which posit that the death penalty has a marginal deterrent effect beyond that of long-term imprisonment, are so limited or flawed that they have failed to undermine consensus.”