This study will assess the evidence on the deterrent effect of the death penalty—whether the threat of execution prevents homicides. The focus will be on studies completed since an earlier National Research Council assessment (National Research Council, 1978). A major objective of this study is to evaluate underlying reasons for the differing conclusions in more recent empirical studies about the effects of the legal status and actual practice of the death penalty on criminal homicide rates. The committee will develop a report about what can be concluded from these studies and also draw conclusions about the potential for future work to improve upon the quality of existing evidence.

Issues and questions to be examined include the following:

1.   Does the available evidence provide a reasonable basis for drawing conclusions about the magnitude of capital punishment’s effect on homicide rates?

2.   Are there differences among the extant analyses that provide a basis for resolving the differences in findings? Are the differences in findings due to inherent limitations in the data? Are there existing statistical methods and/or theoretical perspectives that have yet to be applied that can better address the deterrence question? Are the limitations of existing evidence reflective of a lack of information about the social, economic, and political underpinnings of homicide rates and/or the administration of capital punishment that first must be resolved before the deterrent effect of capital punishment can be determined?

3.   Do potential remedies to shortcomings in the evidence on the deterrent effect of capital punishment have broader applicability for research on the deterrent effect of noncapital sanctions?

In addressing those questions, we focused on the studies that have been undertaken since the earlier assessment (National Research Council, 1978). That assessment has stood largely unchallenged: none of the recent work, whatever its conclusion regarding deterrence, relies on the earlier studies criticized in that report or attempts to rehabilitate the value of those studies.

It is important to make clear what is not in the committee’s charge. Deterrence is but 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 normative retributive arguments that the death penalty is the only appropriate and proportional response to especially heinous crimes; the case against it is sometimes based on



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