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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 [email protected]
Questions?