4. Geographical profiling Flashcards
What is crime mapping?
Analyses spatial patterns of crimes
Identified “hotspots” and “hot places”
Started in USA in early 1900s
Before geographical profiling
The “Chicago group”
Park & Burgess:
- extreme poverty, illness and crime found disproportionately in certain parts
- delinquents lived/operated in certain areas and committed crimes close to home
- delinquency was concentrated in areas of deprivation/poverty/transition
The concentric circle theory
Burgess, 1967:
- link between poverty, lack of affluence and crime
- zone 2 (transition zone) had most delinquency, youth gangs, adult crime and poverty
Broken window hypothesis
Run down buildings, derelict houses, etc. –> higher levels of crime
Social disorganisation
highlights connection between crime patterns and the conditions of residents
Crime pattern theory
Brantingham & Brantingham, 1991:
- most offenders commit most offences close to home, in familiar territory
- distance decay: the further the distance from home, the less likely an offender will commit a crime
What is geographical profiling?
Officers request help from a geoprofiler, who sees spatial patterns in crime
Investigative technique that attempts to provide information on the likely base of operation of someone suspected of serial crime
Used to locate offender’s home or anchor point
Use resources more efficiently - focus on a smaller area
Routine activity theory
Cohen & Felson, 1979:
Crime occurs when 3 elements come together:
* motivated offender
* suitable victim
* absence of a guardian able to protect victim
Used to explain crime victimisation
What is crime victimisation?
Why certain people are victims of predatory crime
Rational choice theory
Cornish & Clark, 1986:
Criminals perform a cost-benefit analysis
Offenders are unlikely to commit crime if risks outweigh the potential benefits
Offenders are unlikely to commit crimes that take them away from familiar surroundings
Canter and Youngs (2009)
The further an offender travels from home, the higher the risks
If an offender travels far way, it’s because increased benefits are expected
What are the key concepts?
Lack of randomness;
Distance decay;
Mental maps;
The circle/centrality theory
Lack of randomness
Crime is not randomly distributed
Offenders make an active choice about where they commit crimes (whether aware of it or not)
The distance travelled by offenders and the spatial distribution of their crimes provide valuable clues about their homes/base of operation
How to extrapolate where offenders are likely to live
Algorithms
Distance decay
Rossmo (1995):
As the distance from an offender’s home increases, the probability s/he will commit a crime decreases
Likely to be a “buffer zone” around offender’s home where unlikely to commit an offence (incase recognised)
For most offenders less than 1/4 mile from home
Size of buffer zones depends of crime type
The “least effort principle”
Research shows that offenders tend to commit crimes close to home (familiarity)
Where is offending most likely to take place?
Where the offender is likely to remain anonymous (not too close to home) but is still familiar with surroundings
Mental maps - cognitive maps
Brantingham & Brantigham, 1991:
Internal representations that help us find out way around
Mental maps stronger for local/familiar areas
More likely to offend somewhere local where the cognitive map is well developed
Mental maps - cognitive scrips
Mental images/plans for how a crime will be carried out
Developed on basis of familiarity with area/routes for escape/meticulous planning (planning how to avoid certain situations, e.g. recognised)
Centrality theory
Canter, 1993:
Domocentricity - the crime spatial patterns of many serial offenders will approximate a circle around their homes/anchor points
Research- accurate for serial rapists, arsonists and murderers
Doesn’t apply to commuters (travel to separate area) or the windshield wiper effect, but does to marauders (live in the middle of crime locations) (Bartol + Bartol, 2013)
Distance travelled varies in accordance with crime type and country
Geographic hunting patterns - criminal hunting styles
Rossmo, 1997:
Hunter - hunts near home (like marauder)
Poacher - travels some distance to hunt (like commuter)
Troller - randomly encounter victims in daily activity
Trapper - draw victims to them
Geographic hunting patterns - Primary victim attack methods + Challenges
Raptor - attacks victim upon encounter
Stalker - follows victim upon encounter, then attacks
Ambusher - attacks victim after being enticed to a location controlled by offender
Challenges: minimal use to investigators, as lack of scientific validity
What does geographic profiling software do?
Produces a 3D probability map (called “jeopardy surface”) showing most likely residence locations for the suspect
What are the 4 main types of geographic profiling software?
- Rigel (Rossmo, Canada)
- Crimestat (Levine, USA)
- Dragnet (Canter, UK)
- Predator (Godwin, USA)
How to interpret a jeopardy surface
High probability areas coloured in red/orange/yellow
Low probability areas highlighted in grey/purple/pink
6 basic assumptions of geographic profiling
- A series of cases are linked to one offender.
- At least 3 or 4 crimes are needed to link them to a single offender.
- Offences should be widely dispersed, with a central location.
4 Offender should have a stable base of operations. - Short time interval between offences.
- Crime series must occur continuously over time.
