Marginal Deterrence and Multiple Murders

This paper examines empirically the state-level impact of capital punishment on multiple murder rates for the period 1995–1999. In baseline tests—tests employing mixed panel data and using an estimation technique combining aspects of both fixed- and random-effects models—we show that executions reduce the single murder rate and that the use of electrocution reduces the murder rate beyond that resulting from lethal injection. These results are not unique. The unique finding of our analysis is that multiple murders are not deterred by execution in any form, quite possibly because the marginal cost of murders after the first is approximately zero. Finally, we offer a brief historical analysis of how the principle of marginal deterrence has been used and suggest how it might be applied in the matter of multiple murders.