Circle Hypothesis
Definition
David Canter and Paul Larkin's 1993 hypothesis that for marauder offenders, the anchor point falls within the circle defined by the two most geographically separated crime sites as the diameter.
- Authors
- David Canter and Paul Larkin
- Year
- 1993
- Applies to
- Marauder-type offenders
- Core claim
- Anchor point lies within the circle drawn on the two furthest-apart crime sites
Common questions
How does this differ from Rossmo's jeopardy surface?+
The circle hypothesis is a simple geometric rule of thumb locating the anchor within one circle, whereas Rossmo's model computes a probability surface across the whole map using a distance-decay function, giving a graded likelihood rather than a single boundary.
Does the circle hypothesis work for commuter offenders?+
No, it was developed for marauders, whose anchor sits within their offending range; commuters travel out from a home base to a separate offending area, so the circle rule does not reliably locate their anchor point.
Why is offender classification checked before applying the hypothesis?+
Applying a marauder-based geometric rule to a commuter's crime series can point an investigation toward the wrong search area entirely, since a commuter's home base can sit well outside the circle drawn from their offence locations.
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...
- 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.
- Distance Decay
- The empirical observation that the probability of an offence location decreases as distance from the offender's anchor point increases, reflecting the rising...
- 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...