Serial killers: criminal psychology, case studies, and detection methods

Serial killers have struck fear in the hearts of people, yet the public remains fascinated and intrigued by the crimes perpetrated by these individuals. There are several theories and factors that have been attributed to serial killers in an attempt to explain their behaviors. Furthermore, by identifying the behaviors that are exhibited by serial killers, law enforcement professionals are able to gather information about these serial killers that will assist in the apprehension of the criminal.

In the majority of serial homicides, a motivating factor, in addition to domination and manipulation of a victim, is the sexual gratification and desire that is experienced by the serial killer. Serial killers murder individuals because they believe, and feel, that the act will fulfill them and they will continue to murder people as long as they can (Douglas 191). The definition of serial killer may be distinguished from that of a spree killer and/or mass murderer through variety of factors. Whereas a spree killer will murder a number of victims at different locales over a short period of time and a mass murderer will play an endgame strategy in which he or she does not expect to survive, a serial killer will hunt humans primarily for the sexual thrill that they derive from the act (14). It is not often that law enforcement officials and behavioral scientists are able to get a first-hand glimpse into the world of a serial killer at the time that the attacks are taking place (Arrigo 98). One of the factors that may prevent law enforcement officials and behavioral scientists from observing serial murders at the time they occur is the cooling off period often exhibited by the criminals perpetrating the crime. Because a serial killer commits murders on at least three separate and distinct occasions, the cooling off period between each crime may last days, weeks, months, or even years (Douglas 190).

Serial killers may also be divided into three different categories including the serial murders of patients by nurses and doctors, the murders of random strangers over long periods of time, and serial sexual homicide (Stone 196). Michael H. Stone in The Anatomy of Evil contends that there are several factors that influence a serial killer's behaviors. The factors that may influence behavior are presented in a nature vs. nurture paradigm with occasional factors falling into a category of mixed and/or unknown origins (201). The factors that Stone considers to pertain to an individual's natural environment include mental illness that is coupled with psychosis, schizophrenia, manic-depression, autism, and Asperger's Syndrome. Also included in the list of natural factors are mental illnesses without psychosis such as ADD and ADHD, alcoholism, epilepsy, and an inordinate sexual drive (201). Personality disorders are considered to be inherent to an individual and are therefore considered to be part of an individual's natural environment; personality disorders include being antisocial, psychopathic, schizoid, sadistic, paranoid, and/or impulsive-aggressive (201). Stone identifies nurtural factors as parental physical/sexual/verbal abuse, parental abandonment and/or neglect, the loss of a parent, absence of a father, separation and/or divorce of the parental unit before the child is 16, and brain disease or damage (201). The factors that Stone considers to be attributed to mixed or unknown origins include paraphilia, juvenile delinquency, substance abuse, alcoholism, conduct disorders that are committed in childhood, animal torture and arson, and rape or other sexual offenses that are committed in adolescence (202). FBI statistics reveal that at least "42% of serial killers have suffered severe physical abuse as children, 43% were sexually molested, and a full 74% were subjected to ongoing psychological torture (Schechter 293).

Serial killers often develop a pattern of behavior and actions that can help law enforcement officials observe and predict future behaviors. The modus operandi, or MO, is present in most, if not all, of their victims and helps the law enforcement officials identify the type of serial killer an individual may be (Arrigo 232). A modus operandi is defined as "repeated patterns of behaviors which are unnecessary to the commission for the crime; provide psychosexual arousal and gratification; and compliment the motive" (232). It is unusual for a serial killer to completely change their MO, however, there is evidence that killers will alter or adapt their MO to better suit their needs.

Criminal profiling is useful and beneficial in helping to apprehend serial killers. Criminal profiling is "the process of inferring distinctive personality characteristics of individuals responsible for committing criminal acts" (Turvey 1). Criminal profiling can also be referred to as psychological profiling, investigative profiling, or crime scene analysis (Arrigo 232). The chief aim of criminal profiling is to determine a criminal's signature, often a part of their MO.

A series, or set, of serial killers that can be identified by their MO are the Boston Strangler and the Hillside Stranglers who strangled their victims to death. According to Vernon Geberth, the Commanding Officer of the Bronx Homicide Task Force, strangulation is one of the most intimate and personal of murders because the killer literally holds their victim's life in their hands; strangulation gives the killer a sense of control over the situation (Geberth).

Albert DeSalvo, dubbed the Boston Strangler, committed his crimes during a two-year period that lasted from June 14, 1962 to January 4, 1964. DeSalvo was accused of killing 13 women, aged 19 to 85, in Boston, Massachusetts and the surrounding New England region. DeSalvo was also known as the "Measuring Man" and the "Green Man" for other crimes he was committing during the time. DeSalvo was able to gain access to many of his victims homes and residences by posing as a maintenance man, deliveryman, or other service provider. The majority of DeSalvo's victims were found to have been raped and strangled with a nylon stocking, while only two of his victims were found to have been stabbed and beaten to death (Schechter 70). Because DeSalvo's crimes were committed throughout the New England region and not constrained to a single city or state, law enforcement jurisdiction was difficult to determine. Ironically, DeSalvo was not arrested for the murders he committed, but rather for the crimes he committed as the "Green Man" (70). It was only after his arrest that DeSalvo revealed that he was behind the serial murders of at least 13 women. DeSalvo was stabbed to death in prison in 1973 (70).