The math of serial murder: Understanding victim numbers and series duration

Abstract

Purpose

This study addresses the complex task of determining the criminal intensity posed by serial killers in a murder series by introducing the Lambda (− rate of killings) to adjust for the time span in a murder series. It focuses on examining factors related to the offender and the crime-commission process that influence victim count in a series. Methods: Generalized estimating equations with a negative binomial and a gamma log link function were used to examine factors predicting victim count in a sample of 1258 serial murder cases.

Results

Results showed that offender criminal history did not predict higher levels of Lambda when assessing victim count alone, but did predict a lower value when series length was accounted for. Killing methods were also significant predictors of a higher Lambda but were less useful when only number of victims was considered. Conclusions: Findings highlight the importance of the rate of killings along with total victim count for a more comprehensive understanding of the series' criminal intensity. This approach has implications for law enforcement and criminal profiling as it offers a more detailed perspective on the immediate threat posed by serial killers.