Behind Rossmo's assumptions: further hypotheses to make geographic profiling more operational

Funded by the Belgian National research fund (FRS-FNRS), I am currently collaborating with several services of the federal police of Belgium (strategic, operational and behavioural analysts) to develop operational techniques to implement geographic profiling – including temporal aspects of crime scene – on the Belgian territory. Belgium is characterized by a small and highly populated territory with a complex road network; which require more concerns about its geographical features than the regular grids of American cities.
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<br />From an operational perspective, few studies have focused on the conditions favouring the application of GP. Rossmo defined five criteria for effective likelihood surface, but these criteria are often difficult to verify with the data gathered during the investigations. This presentation proposes to study the relationships between those applicability hypotheses, crime types, and spatio-temporal aspects of the crime in order to better predict the surface effectiveness.
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<br />Then, we discuss the difficulty to meet those assumptions for serial rapes in Belgium. Non-uniform pattern and multiple residences for offenders are some of the factors hampering those assumptions.
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<br />An unsolved case of rapes submitted by the police illustrates how a GP reasoning is still possible when Rossmo’s criteria are not met. The objective was to delineate a priority area around crime locations for DNA testing as the offender was assumed to be local. The series presents a pattern focusing on two different city centers. For this reason, the likelihood surface was generated under a different assumption than the classical distance decay. Indeed, our analysis of the crimes pattern in relation to the road network points out a new hypothesis for the offender’s spatial behaviour: spatial consistency in travelled distances to commit the crimes instead of a distance decay function.
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<br />This hypothesis was supported by an analysis of the ‘neutrality’ of the series crime locations. Brantingham distinguished crime generators/attractors from neutral places as a function of the attractiveness of place. According to him, distance decay functions can only be applied to neutral places. In our series, it appears that only one location was located in rural area, in a very unattractive place for rapes. By contrast, the others were located in the city centers or near night clubs. We concluded that there was a high probability for the offender to come from this village. Subsequent DNA analyses of the residents of that village confirmed our hypothesis.