GEOFORENSIC TECHNIQUE

Geoforensic Technique

Geoforensic Technique

Introduction

During the investigation of many serial violent crimes, law enforcement officials are confronted with a large volume of information identifying several possible suspects. Several methods have been developed to increase efficiency and focus investigative inquiry in this situation. One such technique is that of geographic profiling, a method of identifying the area of probable residence of an unknown offender based on the location of and the spatial relationships among various crime sites. Once they have identified this area, police can then concentrate their efforts, and a variety of investigative strategies—suspect prioritization, patrol saturation, stakeouts, or neighborhood canvasses—can be employed to identify and apprehend the offender.

The model of geographic profiling (also referred to as “geoforensic analysis”) was developed by D. Kim Rossmo and currently operates as an information management strategy performed by the Vancouver Police Department's Geographic Profiling Section. Upon request, this unit provides support to government agencies responsible for the investigation and prosecution of serial violent crime. The first report is now used by law enforcement agencies on every level throughout North America and Europe. While geographic profiling was designed to support investigative efforts in cases of serial murder, rape, and arson, its area of application has expanded to include serial bombings, bank robbery, and specialized forms of kidnapping.

Theoretical Assumptions

The ability to determine where an offender is likely to be found, based on a series of crime site locations, depends on predictable behavior patterns among offenders as well as their victims. The model of geographic profiling and its validity thus rest upon several theoretical assumptions, among which three are primary.

Routine Activities Theory

Under the routine activity perspective, offered by Lawrence Cohen and Marcus Felson (1979), there are three essential elements that are required in order for a crime to occur: First, there must be the presence of a “motivated offender.” Second, this motivated offender must come into contact with a suitable target. Third, both the motivated offender and suitable target must converge in time and space when there is no capable guardian present. Once these conditions are met, a crime is then able to occur.

In addition to these fundamental elements, routine activity theory provides a framework within which to understand the normal spatial patterns of offenders and victims in everyday life. According to this perspective, what are called “rhythms” are important in identifying and recognizing the normal or routine patterns individuals follow in their day-to-day activities. For example, one can assume that individuals follow, for the most part, a repetitive pattern when traveling to and from work, school, or recreation. Thus, where individuals can be found forms a relatively predictable pattern, with distinct areas traveled between the fundamental anchor points of a person's employment, home, and places of leisure. Routine activities theory, then, provides a theoretical blueprint for understanding spatial mobility patterns of offenders and their victims.

Rational Choice Theory

While routine activities theory provides a framework for identifying patterns of time and space in victim and offender movement, rational choice theory offers insight into the decision-making processes of the ...