Geographic Profiling –An examination of the predictive potential of serial armed robberies

ByPeter Branca

Criminal Justice ModellingWorkshop 11-12 November 03

IntroductionIntroduction

•Background Geographic Profiling •Outline the research project •Overview of the software used•Research results•Outline some investigative strategies

Spatial AnalysisSpatial Analysis•Spatial Analysis to inform public policy can be traced to the 19th Century

•Dr Snow analysed the location of 500 deaths due to a cholera outbreak. Through the use of a map, he successfully identified the source - ending the epidemic

•Crime locations can also be mapped to provide law enforcement with effective insights into crime

• This potential has been significantly improved through the use of Geographic Information Systems (GIS).

Crime MappingCrime Mapping

Density MapsDensity Maps

Hotspots MapsHotspots Maps

Point MapsPoint Maps

Geographic ProfilingGeographic Profiling

“The estimation of spatial behavioural patterns in order to determine the offender’s most probable

home location”Rossmo, 1995 -Vancouver Police Dept.

Why Geographic Profiling?Why Geographic Profiling?

Although there is usually no known relationship between the offender or victim, the locations of these crimes are often known

All travel decisions are constrained by considerations of time, effort and risk

There is evidence which indicates that the offender’s crime locations are influenced by their home/base

gym

home

work

friends

shops

Routine Activity Routine Activity

Crime ActivityCrime Activity

13 Murders and other attacks

Paul Charles Denyer 3 Serial Killings (and an attempted abduction) in Frankston, Victoria - 1993

Distance from offenders home

Number of offences

Distance Distance Decay Decay

Predictive software:Predictive software:

‘Orion’, ‘Dragnet’ and ‘CrimeStat’‘Orion’, ‘Dragnet’ and ‘CrimeStat’

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

Serial Armed Robbery Research Serial Armed Robbery Research Aims Aims --To explore the predictive potential of Geographic Profiling in relation to serial armed robbery.

Testing various spatial analysis techniques, by examining their accuracy in predicting the home location of serial offenders.

MethodologyMethodology

Phase 1- Data Preparation and Analysis

Phase 2- JTC Model Development

Phase 3- Predictive Analysis developed

Phase 4- Results Interpretation

Four phases:

Data Preparation

Data: 28 serial armed robbers - involving a total of 240 offences (Mean of 8.6 crimes per series)

All of the offences and offender home locations were geo-referenced.

Source: Victoria Police

Data AnalysisOpportunity Theory of Travel

Travel to Crime

Distance v $ Amount Stolen

Data Analysis

Marauder & Commuter models ?

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

Data Analysis

Commuter - Street Offences (26%)Marauder - Milkbar (18%) Service Station (17%) Shops (25%)

Data Analysis

Commuter - Syringe (25%)Marauder - Knife (47%)

Data Analysis

Commuter - Foot (14%)Marauder - Bicycle (4%) Vehicle (20%)

It may be possible to identify a Commuter

by examining the Offence/Offender

characteristics

Analysis Software

•MapInfo

•CrimeStat

•MCi

MapInfo Professional - COTS GISsoftware that provides the ability to view and generate maps for presentations and decision making

Analysis Tools - MapInfo

• $1Mil spatial statistical program developed under grant from the National Institute of Justice (NIJ), Washington, DC.

• Developed for Crime Analysis• License is free to researchers and law

enforcement

• Downfall - Can be complex to use

Analysis Tools - CrimeStat

Analysis Tools - MCiMCi - MapInfo/CrimeStat Interface

Specially created for this research project

MapInfo CrimeStatCrimeStatAnalysisCrimeStatCrimeStat

View ResultsView Results

How it all works - Input

CrimeStatCrimeStat

Parameter Settings

CrimeStatCrimeStat

How it all works - Analysis

CrimeStatCrimeStat

How it all works - Output

Visual Analysis - Output

JTC Model DevelopmentCrimeStat - Journey To Crime (JTC)

Models can be based on either :•Mathematical function, or •Empirically derived function

JTC models were developed using sample data

JTC Model DevelopmentMathematical function

Research data was used to determine the best fit (ie. best model/s) against each of the five available models

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 = 12.22%

Analysis Results

JTC Mathematical

Model 1JTC Mathematical

Model 2JTC Calibrated

Model 3Centrography

Model 4

JTC PredictionLevel (1-10)

Percentageof ActivitySpace

JTC PredictionLevel (1-10)

Percentageof ActivitySpace

JTC PredictionLevel (1-10)

Percentageof ActivitySpace

Percentage of ActivitySpace

Mean 2.83 20.73% 2.58 25.51% 3.67 30.73% 26.97%

Standard Deviation 19.09% 15.95% 26.83% 25.16%

Best 1.80% 5.43% 4.28% 0.59%

Worst 67.07% 56.99% 88.05% 92.88% No. times PAS ofless than 25% (92%) 11 (58%) 7 (67%) 8 (58%) 7

Mean(Entire Dataset) 3.81 61.90% 3.38 64.13% 4.56 67.48% 68.43%

Marauder ModelEntire Dataset

Conclusions - Research

Research Indicates:

•International research is consistent with the Australian environment

•It is possible to reduce the area a serial offender is likely to live, based upon crime locations and offence characteristics

•Geographic Profiling can ‘assist’ investigators in the identification and capture of serial offenders

Analysis Results - Further Investigation

•Investigate the relationship between offence characteristics and Marauder/Commuter

• Research utilising larger data samples

•Model other types of serial crimes

Geographic Profiling StrategiesGeographic Profiling Strategies

PriorityPriority List

Suspect Priorityaccording to:

•Home location•Other associations

Suspect Priority

Area Targeting•High police presence•Target Media •Area surveillance•DNA

•Crime investigations can be assisted through the use of Geographic Profiling techniques

•Further studies, involving other types of offence types are needed

•Larger data samples and better quality information is needed (better collection)

Conclusions/Recommendations

Peter Brancapeter.branca@baesystems.com0414983288

Questions?