When I was asked to provide an offender profile for an investigation into a series of rapes and murders around London in 1985, I reasoned that a man who attacked women whom he did not know was likely to have been violent towards women he did know. His violence would be caused by his psychology, not a desire to target strangers.

This came as a surprise to some police officers who thought that the offence they then dismissed as “a domestic” occurred because of the relationship between two individuals — and would not spill over into attacks on strangers. But when John Duffy was eventually convicted as the Railway Rapist it became clear that his rape of his estranged wife at knife-point, which had put him in police records, was an important indicator of the path on which he was set. That crime was eventually was linked to three murders.

Twenty years on, lessons such as this are being learnt by many police forces. I have become aware that at senior levels in the police there is a growing mission not solely to detect violent crimes but to prevent them, with the objective of reducing the number of homicides.

The change from detection to prevention requires a whole new style of policing and we are helping to develop it with police forces in areas as diverse as Merseyside, Ankara and Slovenia. Officers need to diagnose the problem and set in place appropriate interventions to reduce the likelihood of it worsening. By working closely with police officers who deal with violence on a day-to-day basis, one of my PhD students, Keri Nixon, and other members of my team at the Centre for Investigative Psychology have developed a procedure — called PIP [Profiling Intervention Process] — for profiling the context of violence and identifying the appropriate interventions to reduce it. This allows officers called to an incident to go far beyond existing generalised assessments of the seriousness of the incident. The system helps officers to determine how much of the context of a violent incident can be related to a particular individual, how much is a result of endemic problems within a family, or whether it is part of the breakdown of a relationship that can spill over into other areas of violence. It also indicates which agencies and actions should provide the intervention for any particular profile of violence. These interventions can include everything from arresting chronically violent people to counselling for fractured couples.

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