The bulletin first discusses the theory of deterrence and the history of capital punishment, followed by a discussion of the techniques researchers have used to assess the deterrent effect of capital punishment. The featured section of the bulletin presents research evidence on the deterrent effect of capital punishment based on 74 research projects published between 1952 and 2003. In addition to findings on the deterrent effect of capital punishment, the discussion also addresses some of the unintended consequences of the use of capital punishment. The bulletin concludes that although research has not unequivocally determined whether or not capital punishment has a deterrent effect, the weight of the research evidence from various jurisdictions over different time periods continues to support the conclusion that capital punishment has no deterrent effect on the rate of commission of those crimes to which it is applied. Recent research that has supported the deterrence hypothesis, however, will likely revive interest in the debate. The difficulty in making progress to resolve the debate is the limited range of methods researchers can use to analyze the issue. These methods have all been tried, and they do not produce consistent findings. Researchers must now examine the reasons for differing findings under the various research methods. In its conclusion, the bulletin raises the issue of whether capital punishment, as an issue of life and death, should be implemented when three decades of research have yet to provide conclusive evidence that it reduces those crimes to which it attaches. 1 figure, a table that summarizes research findings, and 116 references