10. Forensic - the bottom-up approach

• What is the bottom up approach?

  Unlike the US top-down approach, the British bottom-up model does not begin with fixed typologies. Instead, the profile is 'data-driven' and emerges as the investigator rigorously scrutinises the details of a particular offence.

  The aim is to generate a picture of the offenders' characteristics, routines and background through analysis of the evidence.
• What sort of analysis is carried out with the crime scene evidence?

  Statistical procedures/analysis detect patterns of behaviour that are likely to occur (or coexist) across crime scenes.

  This is done to develop a statistical 'database which then acts as a baseline for comparison. Features of an offence can be matched against this database to suggest potentially important details about the offender, their personal history, family background, etc.
• What is the analysis based on? What is the key concept of this approach?

  Based on psychological concepts

  A central concept is interpersonal coherence - the way an offender behaves at the scene may reflect their behaviour in everyday situations, i.e. their behaviour 'hangs together'. This might tell the police something about how the offender relates to women more generally.
• What is geographical profiling?


  Inferences about the offender based on location
• What is crime mapping?

  The locations of crime scenes are used to infer the likely home or operational base of an offender. Serial offenders restrict their 'work' to areas they are familiar with. Location can also be used alongside psychological theory to create hypotheses about the offender and their modus operandi
• Canter and Larkin proposed two models of offender behaviour:

  1. The marauder - operates close to their home base

  2. The commuter - likely to have travelled a distance away from their usual residence when committing a crime
• What is the circle theory proposed by Canter and Larkin:


  The pattern of offending locations is likely to form a circle around the offender's usual residence, and this becomes more apparent the more offences there are. The offender's spatial decision-making can provide insight into the nature of the offence
• Difference between bottom-up and top-down approach?

  Both are based on crime-scene data. The difference is that the top-down approach uses the data to generate the profile and, from then on, the investigator fits the profile to the crime scene. In the bottom-up version the investigator always starts again at the bottom and generates a profile.
• 1st strength of the bottom-up approach in offender profiling

  That evidence supports investigative psychology

  Canter and Heritage conducted an analysis of 66 sexual assault cases using smallest space analysis. Several behaviours were identified in most cases (e.g. using impersonal language). Each individual displayed a pattern of such behaviours, helps establish whether two or more offences were committed by the same person ('case linkage'). This supports one of the basic principles of investigative psychology (and the bottom-up approach) that people are consistent in their behaviour
• Counterpoint to the 1st strength of the bottom-up approach in offender profiling

  However, the database is made up of only solved crimes which are likely to be those that were straightforward to link together - a circular argument. This suggests that investigative psychology may tell us little about crimes that have few links between them and therefore remain unsolved.
• 2nd strength of the bottom-up approach in offender profiling

  Evidence to support geographical profiling

  Lundrigan and Canter collated information from 120 murder cases in the US. Smallest space analysis revealed spatial consistency - a centre of gravity. Offenders leave home base in different directions when dumping a body but created a circular effect, especially in the case of marauders. This supports the view that geographical information can be used to identify an offender
• 1st limitation of the bottom-up approach in offender profiling

  Geographical profiling may not be sufficient on its own

  Recording of crime is not always accurate, can vary between police forces and an estimated 75% of crimes are not even reported to police. Even if crime data is correct, other factors matter e.g. timing of the offence and age and experience of the offender. This suggests that geographical information alone may not always lead to the successful capture of an offender