In the immediate aftermath of Gregg, an earlier report of the National Research Council (NRC) reviewed the evidence relating to the deterrent effect of the death penalty that had been gathered through the mid-1970s.
Some studies conclude that executions save large numbers of lives; others conclude that executions actually increase homicides; and still others conclude that executions have no effect on homicide rate.
All of these issues are relevant to making a judgment about whether the death penalty is good public policy.
Our charge was also limited to assessing the evidence on the deterrent effect of the death penalty on murder, not the deterrent effect of noncapital sanctions on crime more generally.
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? 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?
CONCLUSION AND RECOMMENDATION: The committee concludes that research to date on the effect of capital punishment on homicide is not informative about whether capital punishment decreases, increases, or has no effect on homicide rates.
Our mandate was not to assess whether competing hypotheses about the existence of marginal deterrence from capital punishment are plausible, but simply to assess whether the empirical studies that we have reviewed provide scientifically valid evidence.
In its deliberations and in this report, the committee has made a concerted effort not to approach this question with a prior assumption about deterrence.
Another major deficiency is the use of incomplete or implausible models of potential murderers’ perceptions of and response to the capital punishment component of a sanction regime.
Without this basic information, it is impossible to draw credible findings about the effect of the death penalty on homicide.