ABSTRACT
Traditionally, profiling has involved the process of predicting the likely socio-demographic characteristics of an offender based on information available at the crime scene. For example, the Crime Classification Manual, a handbook for offender profiling issued by the FBI, explains that, ‘The crime scene is presumed to reflect the murderer's behavior and personality in much the same way as furnishings reveal the homeowner's character’ (Douglas et al., 1992: 21). The idea of inferring one set of characteristics from one set of crime-scene actions relies on two major assumptions. Firstly, there is the issue of behavioural consistency: the variance in the crimes of serial offenders must be smaller than the variance occurring in a random comparison of different offenders. Research findings indicate that this appears to be the case for rapists (Bennell, 1998; Grubin et al., 1997). Criminologists, in adopting a ‘molar’ approach, define behavioural consistency as the probability that an individual will repeatedly commit similar types of offences (Farrington, 1997). In contrast, psychologists have emphasized a ‘molecular’ analysis of criminal behaviour, where behavioural consistency is defined as the repetition of particular aspects of behaviour if the same offender engages in the same type of offence again (Canter, 1995). A number of studies have provided support for the notion of offender consistency. For example, Green et al. (1976) studied the consistency of burglary behaviour. Based on 14 behavioural ‘markers’, Green and his colleagues were able to accurately assign 14 out of 15 cases of burglary to the relevant three burglars. Similarly, Craik and Patrick (1994), Wilson et al. (1997), and Grubin et al. (1997) all concluded that behavioural consistency exists in the crime-scene behaviours of serial rapists, though only to a limited degree.
