A psychological profile is a tool that can help crime investigators by telling them the kind of perpetrator they are seeking. The development of psychological profiling began in the Federal Bureau of Investigation (FBI ) Behavioral Science Unit during the 1960s in an attempt to understand violent criminal behavior. Although psychological profiling has been used in the pursuit of serial killers , it is also applied to the investigation of product tampering , poison pen letter writing, serial bombing, serial rape, kidnapping, arson , and single murders.
A psychological profile is built through evidence from the scene of the crime, which is integrated into psychological theory. Forensic researchers have built a body of knowledge based upon interviews with criminals and data from a wide range and number of crimes. It is important that the profiler has access to all the information about a crime, from witness statements and analysis of physical evidence to photography and autopsy findings. A perpetrator does not leave behind just physical evidence like fingerprints at the scene when he or she commits a crime. Also left behind clues are clues about behavior and personality which are revealed by a study of the scene and all the evidence connected to it.
Victimology, the study of the victim, is an important part of psychological profiling. The investigator wants to know what attracted this perpetrator to this victim and what the relationship was between them. This may shed light on the motivation for the crime which can reveal much about the personality of the perpetrator and maybe the fantasies driving them.
The perpetrator's modus operandi (method of operation or M.O.), which describes the tools and strategies used to carry out the crime, can be very revealing. It demonstrates some of the suspect's behavior that, in turn, is linked to their personality. Forensic psychology has revealed three main types of offenders. The organized offender plans the crime, sometimes in great detail, bringing tools and taking them away again. The type of offender will take care not to leave evidence behind and will also hide or dispose of the body. The organized offender is usually of average to high intelligence with a stable lifestyle. They normally tend to be married and employed. The disorganized offender often leaves a mess. They don't plan or bring tools; instead they use whatever is to hand to carry out their attack. This type of offender lives alone or with a relative, may be unemployed, of lower intelligence, and have a history of mental illness. Their attacks are often accompanied by considerable violence. The third category is the mixed offender, who shows mixed characteristics of the first two types. While their approach may be carefully planned, the assault itself may be frenzied, showing a person losing control over deep-seated urges and fantasies.
The psychological profile of a criminal can be very revealing of their habits, employment, marital status, mental state, and personality traits. A profile works best if the offender displays some form of mental disturbance such as employing torture or mutilation. Some take a trophy away from the victim, possibly an item of no obvious value but of deep symbolic significance to the perpetrator. They may also use a signature, which is a behavioral sign such as positioning the corpse in a certain way or tying a ligature with a complicated knot. This, again, can reflect a specific personality quirk which may be very revealing to the profiler.
Psychological profiling first proved its worth in the capture of Richard Trenton Chase, the so-called "Vampire of Sacramento," who murdered a woman and drank her blood in 1978. Concerned at the brutality of the crime, the FBI called in the profilers. They noted the disorder at the scene and, from a study of body type and mental temperament, concluded the murderer was white, thin, undernourished, and in his mid-twenties. As a disorganized type, he'd be unemployed and live alone. They also guessed he would kill again and, unfortunately, three days later he did. He murdered three people in their own home, stole the family car and then abandoned it. The second murder provided more information to refine the profile. Chase was soon found, living locally. His appearance was just as the profile had suggested. He had a history of mental illness, admitted the crimes, but did not see he had done wrong. He told his interrogators that his own blood was turning to sand, so he had to become a vampire. The profile saved many lives, for Chase had more murders planned and marked down on a calendar found in his room.
see also Criminal profiling.