Modeling Criminal Distance Decay

Mike O’Leary , Towson University

As with the articles in this issue, this introduction reflects the views of the authors and does not necessarily reflect the views of the U.S. Department of Housing and Urban Development.

Criminal distance decay is the fundamental notion that a relationship exists between the distance from an offender’s home base to a potential target location and the likelihood that the offender chooses to offend in that location. This relationship is important both for its operational effect on police agencies and on models for offender behavior. A number of factors influence the distance decay function of an offender, including the local geography and the offender’s decisionmaking process.

This article addresses a study of the interactions between the two-dimensional offense distribution that describes how offenders select targets and the corresponding onedimensional distance decay function. It also presents the calculation of the coefficient of variation for 324 residential burglary series in Baltimore County, Maryland. These data do not support the notion that the distance decay behavior of an individual offender is governed by a number of common choices for distance decay, including the negative exponential, even allowing for the parameters to vary between offenders. Finally, the article examines geographic patterns for residential burglary in Baltimore County and the finding that, although offenses committed in rural portions of the county are committed by offenders with larger travel distances, it does not appear that this variation can be explained simply by the local population density.