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Comparing the predictive accuracy of case linkage methods in serious sexual assaults This publication appears in: Journal of Investigative Psychology and Offender Profiling Authors: J. Winter, J. Lemeire, S. Meganck, G. Rossi and A. Mokros Volume: 10 Issue: 1 Pages: 28-56 Publication Year: 2013
Abstract: The empirical support for linkage analysis is steadily increasing, but the question remains as to what method of linking is the most effective. We compared a more theory-based, dimensional behavioural approach with a rather pragmatic, multivariate behavioural approach with regard to their accuracy in linking serial sexual assaults in a UK sample of serial sexual assaults (n=90) and one-off sexual assaults (n=129). Their respective linkage accuracy was assessed by (1) using seven dimensions derived by non-parametric Mokken scale analysis (MSA) as predictors in discriminant function analysis (DFA) and (2) 46 crime scene characteristics simultaneously in a naïve Bayesian classifier (NBC). The dimensional scales predicted 28.9% of the series correctly, whereas the NBC correctly identified 34.5% of the series. However, asubsequent inclusion of non-serial offences in the target group decreased the amount of correct links in the dimensional approach (MSA-DFA: 8.9% NBC: 32.2%). Receiver operating characteristic analysis was used as a more objective comparison of the two methods under both conditions, confirming that each achieved good accuracies (AUCs=.74-.89), but the NBC performed significantly better than the dimensional approach. The consequences for the practical implementation in behavioural case linkage are discussed.
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