USAToday this morning relates a new review by the National Research Council this past week indicating that in the more than three decades since the national moratorium on the death penalty was lifted, there's been no reliable research to determine whether capital punishment has served as a deterrent to homicide.
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.
USAToday's article said the study panel reviewed the work of "dozens" of researchers since the Supreme Court's 1976 Gregg v. Georgia decision ended a four-year national moratorium on executions.
Carnegie Mellon University professor Daniel Nagin, who chaired the Council's study committee, was quoted as commenting that "fundamental flaws in the research we reviewed make it of no use in answering the question of whether the death penalty affects homicide rates… We recognize that this conclusion may be controversial to some, 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 committee's report brief also notes that "It is important to make clear what the committee's study did not examine. Deterrence is only one of many considerations relevant to deciding whether the death penalty is good public policy. Not all supporters of capital punishment base their argument on deterrent effects, and not all opponents would be affected by persuasive evidence of such effects. The case for capital punishment is sometimes based on arguments that the death penalty is the only appropriate response to especially heinous crimes; the case against it is sometimes based on claims that the sanctity of human life precludes state-sanctioned killings. Other considerations include whether capital punishment can be administered in a nondiscriminatory way, whether the risk of mistakenly executing an innocent person is acceptably small, and the cost of administering the death penalty in comparison with other punishments."