Distance Decay
Definition
The empirical observation that the probability of an offence location decreases as distance from the offender's anchor point increases, reflecting the rising cost and risk of more distant travel.
- Field
- Geographic profiling / environmental criminology
- Pattern
- Offence probability falls as distance from anchor point rises
- Cause cited
- Rising travel cost and risk with distance
- Related model
- Rossmo's jeopardy surface
Common questions
Does distance decay mean offenders never travel far?+
No, it describes a probability gradient, not a hard limit. Most offences cluster nearer the anchor point, but some offenders travel considerable distances, which is why profiling treats it as one weighted input rather than a fixed rule.
How does distance decay differ from a simple buffer zone around a suspect's home?+
A buffer zone assumes near-home offending is uniformly likely up to a cutoff, while distance decay models a continuous probability that changes with distance and typically dips very close to home, the basis of the buffer-zone or safety-zone concept within jeopardy-surface models.
Related terms
- Buffer Zone
- The area immediately around an offender's anchor point where offence probability is suppressed because the offender avoids committing crimes near recognisable locations...
- Circle Hypothesis
- David Canter and Paul Larkin's 1993 hypothesis that for marauder offenders, the anchor point falls within the circle defined by the two...
- Commuter
- An offender who travels from their anchor point into a geographically separate crime area to offend; the circle hypothesis does not reliably...
- Criminal Geographic Targeting (CGT)
- Kim Rossmo's algorithm for geographic profiling, incorporating a distance-decay function modified by a buffer-zone suppression factor; implemented commercially in the Rigel software.
- Geographic Profiling
- A spatial analysis technique originally developed by Kim Rossmo that predicts the likely home or anchor point of a serial offender from...
- Jeopardy Surface
- The probability map output of geographic profiling, rendered as a colour-coded topographic display where high-probability zones for the anchor point appear in...
- Marauder
- An offender who operates radially from a fixed anchor point, committing crimes within a radius around that point and returning to it...
- Rigel
- The commercial software implementing the CGT geographic profiling algorithm, developed by Environmental Criminology Research Inc. in Vancouver and licensed to law-enforcement agencies...