The field of Investigative Psychology (IP) integrates many well-grounded psychological theories to investigate crime and criminal behaviour. IP aims to develop an understanding of crime and criminal behaviour to aid all aspects of policing and court proceedings. There are several components that need to be considered when exploring why an offender commits crime A and not crime B, and indeed, why others choose neither.
First, the type of crime that is committed needs to be considered, however, there is debate over whether individuals show consistency in their offending behaviours. This consistency is typically measured as specialisation and there is evidence for and against the existence of it. Secondly, the motivations for behaviour need to be considered. An individual may find a particular action appropriate under some circumstances but not others and may have a preference towards a particular behavioural style. When an offender explains his or her offending behaviour, it may be accompanied by a justification that is valid to the offender for doing so. It is possible that one type of justification may be more compelling than another; this may vary depending on beliefs and standards. Finally, the individual characteristics of the offender must also be considered. Aspects such as age, gender, or personality may increase or decrease the likelihood that an individual may offend. Each of these factors has been considered empirically within the literature, however, there is no understanding of how these factors influence each other and how they function collectively to increase propensity to commit a particular type of offence.
General principles within Investigative Psychology.
One of the major assumptions of IP is that it is possible to infer offender characteristics from actions carried out during a crime. Canter & Youngs (2009) summarise that these actions may be the type of crime committed, as well as how, or where, it is carried out. The offender characteristics may include any information about the individual who committed that crime which may be of value to the investigation process or any court proceedings which may follow.
This inference development is a central process within IP and is known as the A to C equation, the A’s relate to the actions within a crime and the C’s relate to the characteristics of the offender (Canter, 1993). However, as Youngs (2007) has highlighted, the relationship between these variables is canonical as there will rarely be one action that predicts one characteristic, there are likely to be a range of complexities in the way that these variables relate to each other. As Canter & Youngs (2009) elaborate:
The whole concept of a ‘canonical equation’ shows that small changes in any one variable can influence the overall outcome. A change in the range of crimes considered, or age of victims, or length of time over which the crimes are examined could produce very different predictions of, for instance, criminal history. (P84)
Canter & Youngs (2002) propose that there are limitless possibilities of which actions relate to which characteristics, and as such some form of theoretical framework is necessary to indicate relationships between the two. Canter & Youngs (2009) further highlight that the relationship between actions and characteristics can be thought of as a series of ‘if-then’ statements, however they are careful to point out that arguments made in this way require ‘warrant’ which usually takes the form of well-grounded psychological theories and requires some empirical support before the statement can be accepted as true.
Canter & Youngs (2009) also discuss in some detail, that inferences made between actions and characteristics can vary in how precise they are. These inferences range from specific to general, which they label as tight or loose couplings. The examples that Canter & Youngs propose to describe these levels of specificity are that it may be possible to predict some sort of military background from the level of control used on a rape victim (a loose coupling), whereas the use of specific types of bindings may be related to a particular type of military training (a tight coupling).
The level of specificity can also vary when examining criminal acts or crime scenes. For example, official statistics can reveal how much crime has been reported in any particular area, which would be a very broad level of specificity. However, as Canter (2003) points out in his book ‘Mapping murder’, much can be gained from focusing beyond maps of crime to understand the significance of the places an offender chooses to carry out their offence(s), which would be a very precise level of specificity.
Difficulties in making inferences between actions and characteristics.
Alison, Bennell, Mokros, and Ormerod (2002) suggest that for offender profiling to be useful and valid, there must be consistency and homology in the way an offender behaves. Alison et al (2010) clarify this by stating:
“The consistency assumption held that the variations in actions (i.e. behaviours) of an offender across their series must be less than the variation in actions by all other offenders. The second assumption holds that people who commit crimes in a similar style will have similar background characteristics – called the homology assumption.”(p119).
One of the challenges in drawing conclusions about offender’s characteristics from crime scene information is the view that individuals who carry out a crime in a similar way should be similar in their characteristics (Mokros & Alsison, 2002). Shoda, Mischel and Wright (1994) are keen to highlight that the behaviour an offender exhibits is conditional on the situation he or she is in. Mokros & Alison (2002) support this argument and point out that situational influences may inhibit the possibility of inferring offender characteristics from crime scene information, as they state “…it is possible that the neglect of situational influences seriously confounds any homology.” (p40). An example of how context and individual situation can affect findings is found in a study by Beauregard et al (2007), they found that contextual factors such as familiarity with the environment and type of offence site can influence the way serial sex offenders carry out an offence.
However, there is evidence to suggest that behaviour can be stable across crimes for other types of offences. For example, Woodhams & Toye (2007) reported that offence behaviour was found to be consistent in commercial robbery, and Bennell and Jones (2005) report consistency in behaviour for burglary. Behavioural consistency has been established for a number of offence types including sexual assault (Santtilla, Junkkila & Sandnabba, 2005), burglary (Goodwill & Alison, 2006), and arson (Santtila, Fritzon & Tamelander, 2004)
