Testing the Effectiveness of Geo-
Behavioural Profiling Systems
Professor David Canter
&
Laura Hammond
Director, Centre for Investigative Psychology
The University of Liverpool,UK www.i-psy.com

92 offence series in a London borough.
All identified series over four years/

The ‘canonical’ map
Chapman 8.9 – 6.00
Nichols 31.8 –3.40
Kelly 9.11- 7.00?
Stride 30.9 – 1.00
Eddowes 30.9 – 1.45

The ‘canonical’ map

Circle Hypothesis Calculation to Locate Ripper’s Base

Central Circle in Whitechapel

Centre of Gravity of Murder Locations

 Criminal Range
 Decay Functions

Criminal ‘range’

The Distance Decay Function,
An example from serial arsonists
25
20
35
30
15
10
5
0
0-0.1
0.51-0.99
0.11-0.5
1.51-2.00
1.00-1.5
2.01-2.5
2.51-3
3.01-4
4.01-5
5.01-6
6.01-7
7.01-8
10+
Range of Distances traveled by Arsonists

Optimal Function of Distance from Offence to ‘Home’

Offence Map:
Developing the Search Tool that incorporates various distance functions.
1st Crime
2nd
4th
3rd
5th

The system assigns a priority to each known offender using various criteria.
Prioritised search area
226
48
124
124
Offender ID
124
427
427
Address
Location A
Location B
Location C
Location D
Location E
Location F
Location G
Probability
0.28574311864
0.27038233898
0.26035169492
0.25577861017
0.23282991525
0.22445984746
0.21932662712
0
0
0.3
0
0
0
MO
Match
0

Criteria
• Distance from centre of circle defined by 2 furthest crimes
• Distance from centre of gravity (centroid)
• Optimum negative log decay function
• Negative log decay function with buffer
50% of actual offenders are in the top 5 prioritized just by geographical location. iOPS allows this to be improved by also using M.O. matching.

(N = 92)
COMPARISON OF 15 DIFFERENT MODELS
Model Mean Rank (S.D) Median
Rank
8.86 (8.446) 4 Exponential Function - High B-value
Logarithmic Function -Low B-value 9.04 (8.402)
Logarithmic Function -High B-value
Centre of Gravity
8.92 (8.350)
9.21 (8.256)
Logarithmic Function -Optimal B-value 8.95 (8.349)
Logarithmic Function with Buffer Zone- Optimal B-value 9.73 (8.674)
Exponential Function - Low B-value 10.18 (8.411)
4.5
5
5
5
5.5
7
Exponential Function - Optimal B-value 10.55 (8.461)
Exponential Function with Buffer Zone- Optimal B-value 10.61 (8.888)
Last Offence 11.11 (8.416)
7
7
9
11.96 (8.424) 10..5
First Offence
Centre of Minimum Distance 12.52 (8.066) 14
Centre of Circle 15.15 (7.536) 21
Straight Linear Function 21.00 ( .000) 21

Need for more context specific examination of crime patterns
Taking account of
 Land use
 Opportunities for crime
 Guardianship
 Targeting
 Transport routes
 Temporal sequences

Offender
34 crimes
1 home location
Offender 1:
34 CRIMES
1 HOME LOCATION

Offender 2:
34 CRIMES
1 HOME LOCATION
Offender
34 crimes
1 home location

2 Offenders with different distributions of crimse in relation to Southside Centre in
Wandsworth
Southside Centre
Offender
34 crimes
1 home location
Offender
34 crimes
1 home location

EXAMPLES FROM BURLGARIES IN WANDSWORTH
PNC data
12 offenders
All crime types
1992-present
Offender 1:
10 CRIMES
2 HOME LOCATIONS

Offender 8:
24 CRIMES
1 HOME LOCATION

Offender 3:
20 CRIMES
3 HOME LOCATIONS

Offender 2:
21 CRIMES
3 HOME LOCATIONS

Offender 7:
13 CRIMES
2 HOME LOCATIONS

Offender 5:
19 CRIMES
3 HOME LOCATIONS

Offender 11:
48 CRIMES
3 HOME LOCATIONS

Offender 12:
53 CRIMES
2 HOME LOCATIONS