Ch. 3 Geographic Profiling + crime linkage

Geographic profiling definition and purpose

Determine the probable area of offender’s residence. It prioritizes the investigation, identifies repeated criminal activity areas, and guides door-to-door inquiries.

How geographic profiling differs from criminal profiling

It uses human geography and spatial patterns. There is extensive empirical evidence.

Home-to-crime

A measure of offender’s spatial decision

Average crime trip

Relatively short: 5-6km. Most offenders live within the area covered by their criminal activities.

Mode of transportation’s effect on crime

More efficient vehicles → longer distances

Distance decay

Offending frequency decreases as they move further from homes

Spatial behaviour

Humans are very lazy. “Fast and frugal”. Distance travelled by offender suggests they do not put too much effort into deciding where to commit the crime

Violent crimes vs. property crimes

Violent crimes have shorter distance traveled than property crimes

3 types of murder

• Travelling: commits murders while traveling throughout different areas 28%

• Local: commits murders close to home 45-58%

• Place-specific: consistent space 27%

Circle hypothesis

An area bounded by the distance between the two furthest crime locations

Commuter model

locating commuters are much more difficult, more possibilities of home location

Marauder model

The offender stays close to home

Routine activities effect

Crime is a result of every day opportunity, and their residence is part of their routine.

Rational choice effect

Crime is an outcome of choices. Weighs benefits with costs of crime. Choose to commit crimes near home, as these are areas they know the best (minimize risks)

Crime pattern effect

A combination of routine and choice

Bounded rationality

Recognizes, actions often have to be taken on the basis of decision making. Combines all previous factors

Rigel software

Created by Dr. Kim Rossmo. A distance decay function that operates using probability. Ex. CrimeStat and Dragnet. Can be very expensive

Spatial distribution strategies

Calculates a central location, simple, uses center of gravity.

Accuracy of Rigel

Reduces effort by 94%

Accuracy of Dragnet

89% reduced effort.

ViCAP

Violent crime apprehension created by the FBI. Tries to avoid linkage blindness

ViCLAS

Violent crimes linkage analysis system created by the RCMP.

ViCLAS procedure

1. An officer enters all data into a paper or e-booklet

2. Submit it to quality control

3. An officer enters data from solved and unsolved cases

4. Trained analysts search the database for potential links

5. Investigators are informed about potential links

Assumptions behind ViCLAS

The data in the system is reliable and accurate. Assumes behavioural consistency and distinctiveness. Assumes it is possible to identify links

Critiques of ViCLAS

Inter-rater reliability is low. Police may make mistakes during data entry: Garbage in and garbage out. There is no evaluation of the ViCLAS data accuracy. Fails to account for situational factors; the assumption of behavioural stability is questionable. Officer’s ability to link crime is low.

Reasons for criminal profiling pseudoscience - errors in messages

Anecdotes, repetition of “profiling works”, counting hits and dismissing misses, falsely self-proclaimed experts.

Method of interpreting profiles

Ambiguity is interpreted to match the suspect.

• Ambiguity leads to profile matching a wide variety of suspects

• Can lead to confirmation bias

Theoretical assumptions

Homology, behavioural consistency, behavioural differentiation.

Definition for criminal profiling

There is no single definition, however it uses a crime scene’s information to predict an unknown perpetrator’s demographic and personality characteristics.

Classic trait theory

Individuals should behave the same across different situations because their internal traits primarily determine behaviours. Situation matters.

Support for traits of criminal profiling

Limited empirical support

Purpose of criminal profiling

Suspect prioritization, new lines of inquiry, flush out offender, determine dangerousness, interrogation/cross-examination, scientific research.

Criticisms of criminal profiling

Process lack of standards: definition, credentials, application

Contents of profiles

Unsubstantiated opinion, unverifiable details, ambiguous details, opposing alternatives, known information

The amount of profiles that were predictions about the offender

25%

Impact of ambiguity

Multiple interpretations → confirmation bias

Profiler vs. lay people finding

Low level of objective accuracy in profilers’ predictions. Profilers don’t want to be tested. Supports come from common sense rationale

Reasons for pseudoscience - errors in cognitive processing

Pattern seeking, ambiguity, imitation, mistaking fiction for facts

Features of pseudoscience

A tendency to invoke ad hoc hypotheses, intellectual stagnation, reliance on anecdotes and testimonials to support claims