Lesson 2: Bottom-Up Approach To Offender Profiling

Question 1

The Bottom-Up Approach

Answer 1

The bottom-up approach is a data-driven approach that involves using data from crime scene and victim to build a statistical database. Statistical information is analysed to find relationships between crimes.

Question 2

Investigative Psychology

Answer 2

One assumption of investigative psychology is interpersonal coherence. This is the idea that the offender behaves consistently at the crime scene and in real life. For example, whilst some rapists want to control and humiliate their victim, others can be apologetic. This might tell the police how the offender relates to women more generally.

Another assumption of investigative psychology is significance of time and place. Details of the time the crime occurred, and the place it occurred in, may indicate where the offender is based (e.g. where they live and work) or their mode of travel (e.g. train or car).

Forensic awareness describes individuals who have made an attempt to ‘cover their tracks’ (i.e. hide the body/murder weapon or clean the crime scene). Their behaviour may indicate that they have been the subject of police interrogation in the past, or even that the police already have their DNA or fingerprints on file.

Question 3

Advantages of Bottom-Up Approach

Answer 3

+ The bottom-up approach emphasises the importance of data, psychological theory and statistical analysis which makes it more objective and scientific than the top-down approach which is far more reliant on intuition.

+ Bottom-up profiling, unlike top-down profiling, can be applied to a wide variety of crimes, such as burglary and theft, not just violent crimes, like murder and rape.

Question 4

Disadvantages of Bottom-Up Approach

Answer 4

• The success of bottom-up profiling depends on accurate and detailed records being kept on criminal databases.
• Kocsis et al. (2002) found that chemistry students produced a more accurate offender profile than experienced senior detectives. This implies that the bottom-up approach is little more than common sense and guess work.
• There have been some significant failures when using bottom-up profiling. In 1992, 21 year old Rachel Nickell was stabbed 47 times and sexually assaulted in a frenzied attack on Wimbledon Common. In 2008, following examination of forensic evidence, Robert Napper was convicted of the murder. He had been ruled out early on in the initial investigation because he was several inches taller than the profile had claimed the offender would be. Robert Napper killed more victims before he was finally caught.

Question 5

Geographical Profiling

Answer 5

Geographical profiling is the study of spatial behaviour in relation to crime and offenders. It focuses on the location of the crime, and evidence of the extent of the criminal’s local knowledge, as clues to the offender’s life, job and habits. Relevant data includes the crime scene, local crime statistics, local transport, and geographical spread of similar crimes.

Crime mapping and analysis of spatial decision making can reveal whether an offender is a marauder (commits crime close to home) or commuter (who is likely to have travelled a distance away from their home to commit crime somewhere they are familiar).

Question 6

Three key principles in geographical profiling:

Answer 6

1. Least-Effort – A criminal will not travel further than they have to in order to commit a crime and therefore crimes usually occur in a criminal’s locality.
2. Distance Decay – Offenders tend to commit more crimes closer to home than farther away.
3. Centre of Gravity Hypothesis – Where the offender is based will be the place which simultaneously has the minimum possible distance to each of the offence locations.

Question 7

Advantages of geographical profiling

Answer 7

+ Lundrigan and Canter (2001) collated information from 120 murder cases involving serial killers in the US. The location of each body disposal site was plotted and a centre of gravity identified. The offender’s base was invariably in the centre of the pattern. This effect was more noticeable for marauders.

+ One successful use of geographical profiling was the identification of John Duffy known as the ‘Railway Rapist’. Duffy had committed several rapes and murders around railway station in North London in the 1980s. Canter studied the location of the crimes. This helped him to identify where the attacker lived and the resulting pattern suggested the offender was a marauder.

Question 8

Disadvantages of Geographical profiling

Answer 8

• Geographical profiling is not useful for financial crimes or crimes of passion where the offender’s behaviour is not necessarily linked to a specific location.