ECRI Environmental Criminology Research Inc.

ECRI Home : Geographic Profiling : How does Geographic Profiling work

The locations where crimes happen are not completely random, but instead often have a degree of underlying spatial structure. As chaotic as they may sometimes appear to be, there is often a rationality influencing the geography of their occurrence. Crimes tend to occur at locations where, in terms of profit and risk, offenders find suitable victims/targets. As an offender travels between his home, workplace, and social activity sites, his or her activity space (composed of these locations and their connecting paths) describe an awareness region which forms part of a larger mental map—an "image of the city" built upon experience and knowledge.

The input to the geographic profiling system is a series of discrete events tied to specific geographic locations. The software presents the results in the form of a 2-D or 3-D result value map showing the most-probable locations of the centre of activity. In the 3-D image, the dark red area predicts, in this case, the street containing the offender’s residence, with a 70% confidence level.

This application relies on certain known propensities of serial criminals which support this type of analysis, such as a tendency to hunt in known areas, a desire to disguise the home location, quantifiable criteria for perceived distance to crime sites, and an identifiable set of characteristics relating the crimes to a single serial criminal.

The calculation employed to derive the output map from the input data is based on a complex statistical calculation, modified by an application-specific function based on the type of input data and the type of analysis to be performed.

Geographic profiling depends heavily on two key factors:

Valid linkage analysis to determine that a set of crime sites belong to the same series
Valid geographic modeling of the travel distance to crime sites for a particular type of crime, criminal, and geographic area

The first factor is the responsibility of a linkage analysis system such as ViCLAS or VICAP. The second is embodied in Rigel™, ECRI’s Geographic Profiling system.