Forensic Psychology For Dummies (58 page)

Keeps to himself, with one or two close friends.

The ideas that I used to produce the ‘profile’ of John Duffy are all derived from my
consistency principle,
which is that what an offender does in a crime is an expression of how he behaves in other non-criminal situations. Of course, his actions during a crime are more extreme than in other situations, but they’re still consistent with them. Therefore, what he does in a crime can be taken as a direct indication of the sort of person he is.

Various, more detailed, aspects follow from this conclusion:

The
familiarity
that a person exhibits in the crime reveals what he’s normally familiar with. So, in this case, the area of his criminal activity would relate to places he knew from his usual activity (this relates to the routine activity theory that I describe in the later sidebar ‘Staying close to home’). Duffy’s crimes spread out across London, however, and so I hypothesised that initially he’d attacked near to areas he was familiar with, and then begin to look for opportunities farther afield, where he wouldn’t be recognised. His behaviour, as described by his victims, had become more planned and determined, which also fitted this idea. This insight led to the conclusion that his earliest attacks would be the best indicators of where he was based. This process is an early development of ‘geographical offender profiling’, which I discuss in the later section ‘Locating offenders geographically’.

His
emotional responses
in the crime would be an indicator of his emotions in other situations. This offender was a man violently attacking young women, and so it was reasonable to assume that he would be known as a violent person. The point here was to draw attention to his violence rather than the sexual nature of the crimes. Such violence was likely to have previously brought him to police attention.

His
social interaction
in the crime revealed that he was able to initially relate to his victims before he attacked them. This suggested that he was able to have a relationship with a woman that wasn’t entirely vicious. Perhaps naïvely on my part, I assumed they wouldn’t have had any children otherwise he wouldn’t have attacked young women as he did. Since that time (a quarter of a century ago) I’ve realised that married men with children can be much nastier than I ever thought possible.

His
intellectual ability
as revealed in his planning of the crimes indicated that he would have a job that wasn’t a low-level manual one but had some skill associated with it, like being a carpenter (which he was).

His
skills
may also have been relevant, for example in understanding the details of how he bound and controlled his victims, but were less obvious in this case than in many others.

His
criminal habits,
that were the crimes themselves, suggested that the suspect didn’t normally relate well to other people, and like many violent sex offenders had very few friends and little contact with other people.

I drew the other information in the ‘profile’ from witness descriptions and the forensic results of the police. They were carefully studied to provide a coherent set of the most probable information that the police could work with.

As I hope the case illustrates, the number of pointers in a ‘profile’ aren’t necessarily of direct help to the investigation, but they do provide the key guiding points. You may get dozens of irrelevant details right (such as the car he drives, his background in burglary and his knowledge of firearms) and yet get one crucial fact wrong (such as the fact that a woman rather than a man committed the crimes). Clearly, in this case the ‘profile’ would be useless, which is why the current preference is a move away from providing a ‘pen-picture’ to giving guidance on all aspects of an investigation.

Demythologising ‘profiling’

The notion of ‘offender profiling’ is so prevalent in popular culture that a number of myths about it have been absorbed into the public consciousness. For the record, none of the following claims are true:

‘Offender profiling’ is an invention of the late 20th century.