John Duffy and David Mulcahy raped and killed 19 women in England between 1982 and 1986. Psychologist David Canter studied details of the crimes and created a profile of the rapists’ traits, personality, and habits. His applied profile led to the prompt arrest, charge and conviction of railway rapist John Duffy, in the south of England.
The profile said that the rapist would reside in the area near some of the attacks. It also said he would live with a girlfriend or wife and be childless. The profile gave physical characteristic of the age, blood fluids and handwriting. He would be in his latter 20s; and his blood fluids would contain ABO antigens. His right hand would be dominant.
Canter predicted that the rapist would be partially or skilled in his job. The profile also said the perpetrator worked weekends. Canter believed that the rapist would know the railway system. The individual also would have a criminal record of violence. Duffy fit most of the profile, including a criminal conviction for raping his wife. Duffy’s knifepoint attack against his wife placed him at the top of suspect list.
After Duffy followed a woman in a secluded park, police questioned him about the rape and murder that had occurred in an area near a park. Duffy was arrested the next day. The profile Canter developed matched 13 out of 17 details about Duffy’s habits and lifestyle.
From Canter’s profile, law enforcement officials determined that Duffy did not commit all of the crimes. They knew that he had a partner in crime. Twelve years after the attacks and nine years after Duffy was convicted, he revealed the name of his accomplice, David Mulcahy. It was Mucahy who had committed murder, not Duffy. Because of the accuracy of Canter’s predictions psychologists are now commonly used in identifying serial killers.
Offender or psychological profiling, is a strategy that law agencies world wide use in attempting to identify unknown offenders. This type of investigating tool looks at the crime, the manner in which it was committed, weapons used, and etc. and then tries to identify the nature and type of individual to commit such a crime.
In 1986, Dr. David Canter became the first to use this type of strategy in his efforts to help English police capture the “Railway Rapist” Dr. Canter, an expert in both psychology and criminology identified 17 character traits that the unsub would have or exhibit. When John Duffy, renamed the “Railway Killer” because he ended up killing one of his victims, was arrested, 13 of the 17 identifiers turned out to be accurate.
The Railway Rapist crimes of Duffy and Mulcahy represented one of the first cases where police profiling was critical to its solving. In the mid 1980s, the Railway Rapist was elusive to police techniques. Rapes escalated into murders with little progress being made. Professor David Canter was brought in to develop a profile of the attacker. Canter created his profile based on the crimes, their scenes, and the general nature of the offenses. Unheard of at the time in British law enforcement techniques, his profile proved to be invaluable. He deduced that the offender was married, but childless, living in a particular area, and that a history of domestic violence had to be present. This helped to limit the field and using these and other components offered in the profile, the rape and death of a Dutch schoolgirl became the moment when police were able to link profile and action, and apprehend Duffy, with his accomplice, Mulcahey, arrested some time later.
Even though police had linked a series of sexual assaults and three murders to a single man they did not have a solid suspect. The police called in psychologist David Canter to help them develop a profile of the killer. Canter developed the idea of where the killer would be living using his circle theory. He did this by plotting out where the crimes had taken place and drawing a circle around the plot. Using the circle theory the criminal should be found living within the circle. This was true in the Duffy case (Crane, 1995). Canter went through the details of each crime, making note of details such as the nature of the victim, time of day, location, et cetera. He then developed a profile of the probable offender that contained 17 personality, character, and geographical indicators (Crane, 1995, Edwards, 2008).