A Google Scholar search turned this up: https://www.journals.uchicago.edu/doi/abs/10.1086/421571 https://www.journals.uchicago.edu/doi/abs/10.1086/421571 > Re

A Google Scholar search turned this up: https://www.journals.uchicago.edu/doi/abs/10.1086/421571 https://www.journals.uchicago.edu/doi/abs/10.1086/421571 > Results from least squares and negative binomial estimations indicate that capital punishment does deter: each execution results in, on average, three fewer murders. In addition, capital punishment deters murders previously believed to be undeterrable: crimes of passion and murders by intimates. Moreover, murders of both African‐American and white victims decrease after executions, which suggests that capital punishment benefits people of all races. However, longer waits on death row before execution lessen the deterrence. Specifically, one less murder is committed for every 2.75‐year reduction in death row waits. Thus, recent legislation to shorten the wait should strengthen capital punishment's deterrent effect.