If deterrence is a communication effect as Gibbs and others contend, then Chicago provides an ideal research setting, since there is close geographic proximity between the place where first degree murders are committed and the place where the convicted murderers are executed. Accordingly, Chicago residents, including would-be killers, should have had a more direct awareness of murder and its possible consequence (the certainty of execution) than residents of larger jurisdictions such as States or the Nation. The model used represents the hypothesis that the monthly number of first degree murders is a function of the number of executions for first degree murder, the certainty of arrest for first degree murder, the certainty of imprisonment for first degree murder, population density, the percent of the city's budget expended on public assistance for the homeless and other needy adults and children and the season of the year. To examine the effect of executions on first degree murders, a series of multiple regresson analyses were performed where various execution measures and time lag structures were considered. In addition, more general monthly homicide figures similar to those included in the FBI's category of murder and nonnegligent manslaughter were considered in the analysis for comparative purposes and to determine the impact of executions on total criminal homicides in Chicago. In line with the brutalization argument, this analysis suggests that the net effect of executions may well have been to increase rather than decrease Chicago first degree murders and total criminal homicides. This finding is consistent with a number of early and more recent investigations of the brutalization effect of capital punishment in the United States and is only partially at odds with one study. Further, the findings are consistent with the fact that not a single reputable study has yet shown that capital punishment is an effective deterrent to murder. Tabular data and 83 footnotes are provided.