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Abstract

The effectiveness of a geographical decision support tool (Dragnet) for locating the base of serial offenders was compared across 570 models comprised of a range of negative exponential functions, buffer zone components, and normalization parameters. The models were applied to the body disposal locations within each series for 70 U.S. serial killers. Two normalization parameters were compared for all functions. The test of effectiveness was a specifically defined measure of search cost. When applied to the Dragnet predictions it was found that the specially developed normalization parameter (QRange) produced the optimal search costs. The optimal search cost was also found to be for a function that did not include any buffer zone. The optimal, average search cost across the whole sample was 11% of the defined search area. Fifty-one percent of the offenders resided in the first 5% of the search area, with 87% in the first 25%. All resided in the total defined search area. These results support the potential for operational tools using such procedures as well as contributing to our understanding of criminal's geographical behavior. The applicability to other forms of serial crime is considered.

Prediction of serial perpetrator residence: Part I—Induction of models utilising spatio‐temporal routing functions and investigative information

“…The underlying basis for such strategies is the 'circle hypothesis' which states that a perpetrator who commits a series of crimes leaves their home base, commits a crime, then returns to the home base, and therefore resides within a circle constructed by the diameter of the two incident locations farthest apart (Canter & Larkin, 1993). Studies (Canter et al, 2000;Canter & Larkin, 1993;Kocsis & Irwin, 1997;Snook et al, 2004) have demonstrated evidence for the validity of the circle hypothesis. Formulae for spatial distribution strategies which use the set of incident coordinates in each formula to achieve a centrographic point prediction for the offender residence.…”

More than an Offender Location Tool: Geographic Profiling and Body Deposition Sites

“…Popular software like Rigel Analyst, CrimeStat, and Dragnet produce similar outputs, as they are based on a distance decay algorithm (Canter et al 2000;Canter and Hammond 2006;Rich and Shively 2004). After incorporating important offender information (a non-exhaustive list included above), the software places a grid over an area of interest and then calculates the likelihood that the offender's anchor point is within each grid square (Rich and Shively 2004).…”

Statistical foundations of ecological rationality

“…Example 1: Geographical Criminal Profiling. A guiding concern for geographical criminal profiling is achieving low prediction error, and the field progresses in large part through the competitive testing of diverse models ranging from the centroid method to sophisticated probabilistic models (e.g., Rossmo, 1999;Canter et al, 2000;Snook et al, 2005;Levine and Block, 2011). This seems like an unlikely field to harbor a bias bias, yet the bias/variance perspective appears to be unfamiliar to researchers in this area 2 .…”