Geographic Profiling in AustraliaGeographic Profiling in Australia – –An examination of the predictive potential of serial armed An examination of the predictive potential of serial armed robberies in the Australian Environmentrobberies in the Australian Environment

ByPeter Branca

The Seventh Annual International The Seventh Annual International Crime Mapping Research ConferenceCrime Mapping Research ConferenceMarch 31- April 3, 2004: Boston , MassachusettsMarch 31- April 3, 2004: Boston , Massachusetts

IntroductionIntroduction

•Outline of research in Australia •Serial Armed Robbery Research

–Environment–Data analysis–Results–Conclusions

•Kocsis & Irwin (1997) examined serial rape, arson and burglary - support Canter’s ‘Circle Theory’

•Catalano (2001) examined the spatial behaviour patterns of serial robbery in Perth - criminological theories were ‘helpful’ in predictions

•Kocsis et al (2002) assessed the ‘Circle Theory’ for Geographic Psychological Profiling - rural town burglaries 50/50 Commuter and Marauder

•Spencer - (Unpublished) PhD research into spatial patterns of serial sex offences - both Commuter and Marauder behaviour exhibited by same offenders, utility of Dragnet and CrimeStat II investigated

Research In Australia

Few studies have been reported in relation to the geography of serial crime in Australia.

International Research -

Focus on the home being central to serial crime locations.

Centrography Journey to CrimeRoutine Activity TheoryCircle Theory

Centrographic Analysis

Refers to the single location that is the shortest distance to each crime site in the series.

Centroid can be easily calculated using a GIS

gym

home

work

friends

shops

Routine ActivityRoutine Activity

and Journey to and Journey to Crime (JTC) Crime (JTC)

Crime ActivityCrime Activity

Commuter Marauder

Prof. David Canter’s

‘Circle Theory’ - Criminal Range

87% of serial sexual offenders were found to be Marauders

Computer Programs - JTC

Rigel

Dragnet

Predator

CrimeStat

Research Aims - Research Aims - Serial Armed Robbery Serial Armed Robbery in Victoriain Victoria

To explore the predictive potential of Geographic Profiling in relation to serial armed robbery in Victoria, Australia.

Utilising Journey to Crime (JTC) and Centroid calculations to predict the home location of serial offenders.

20 Million People

Melbourne

Sydney

Australia - Australia - (a Quick Geography Lesson)(a Quick Geography Lesson)

Victoria(25%) 4.8 Million

Greater Melbourne3.2 Million

DataData

28 serial armed robbers

Total of 240 offences (Mean of 8.6 crimes per series).

Source: Victoria Police

The vast majority of offenders were males 92.9%.

Average offenders’ age 31.5 years.

The youngest offender was 20 and the oldest was 47.

Knife was the most common weapon used (34.6%).

Syringes exceeded firearms.

Data Analysis

Data AnalysisOpportunity Theory of Travel

Travel to Crime

Distance v $ Amount Stolen

Data Analysis

Marauder or Commuter ?

12 of the 28 series, or 43%, fitted the description of the Marauder model (Group most effective for Geo Profiling)

Data Analysis

Commuter - Street Offences 26%Marauder - Milkbars (Convenience Store) 18%, Other Shops 25%, Service (GAS) Stations 17%

Data Analysis

Commuter - Syringe 25%Marauder - Knife 47%

Data Analysis

Offender Average Age (Mar - 33yrs, Com - 31yrs)

Average Number of Offences (Mar - 11, Com - 7)

Day of the Week (Mar - Sundays, Com - early in the week)

Average Value Stolen (Mar - $1600, Com - $1200)

Mode of Transport (Mar - Bicycle) *Largely unknown

Other less significant comparisons were:

It may be possible to differentiate between the

Marauder and Commuter behaviour by examining

the Offender and Offence Characteristics

Conclusion

Commuter Marauder

?

Software used for analysis

•MapInfo

•CrimeStat

•MCi

Analysis Tools - MCiMCi - MapInfo/CrimeStat Interface

Specially created for this research project

MapInfo CrimeStatCrimeStatAnalysisCrimeStatCrimeStat

View ResultsView Results

Visual Analysis - Output

JTC Model DevelopmentCrimeStat - Journey To Crime (JTC)

Models can be based on either :

•Mathematical function, or

•Empirically derived function

Ned Levine. CrimeStat: A Spatial Statistics Program for the Analysis of Crime Incident Locations (v 2.0).

JTC Model Development

Mathematical function

The following methodology was used :

1. Calculate the Euclidean JTC distances using the research data .

2. Group the distances into appropriate distance intervals (ie range bins).

3. Graphically display the data to assess the central tendency and spread.

4. Generate probability distributions using functions to determine the model that best represents the data.

5. Fit the frequency distribution model(s) to calculate the appropriate parameters required by CrimeStat.

6. Compare models to the original data and select the best fit.

(5 Models Available)

Culling the data for modeling

To remove:

Commuters

Outliers

Best Fit - Mathematical Models

Distance Km

Linear Truncated @ 30ks

(Model 1)

Adj R2 0.83

Negative Exponential*excluding outliers(Model 2)

Adj R2 0.68

Empirically Derived (Calibrated) Model Development

Developed with the research dataset

Prediction Analysis

JTC Predictions:Models 1 & 2 (Mathematical functions)Model 3 (Empirical Model - Calibrated)Model 4 (Centrography)

Prediction Analysis

JTC Predictions (Model 1, 2 & 3)

Prediction Analysis

Model 4 (Centrography)

Prediction Analysis - Evaluation

Percentage of Activity Space (PAS):

(Predicted Area / Activity Space) * 100 = PAS

(2.27/ 23.27)* 100 = 9.75%

PredictedArea

Analysis Results

Marauder ModelEntire Dataset

Conclusions - Research

•Australian findings are consistent with international research

•The spatial behaviour of serial armed robbers is consistent to findings of other types of serial violent offenders

•It may be possible to identify a Marauder based upon offender/offence characteristics

Research Indicates:

Analysis Results - Further Investigation

•Identify a predictive relationship between offence characteristics and Marauder/Commuter behaviour patterns

• Research utilising larger data samples and other offence types should be investigated

•Need for JTC software programs with greater flexibility in relation to the mathematical models available

Peter Branca

psb8@bigpond.com

+61 (0) 419427997

Thank YouThank You