All homicide cases represent their own set of investigative and administrative challenges for the police departments who must close them. Although each police department’s administration may be slightly different, many aspects of murder investigation are similar and even standard. Serial murder, however, is a unique crime, with unique characteristics, that often spans the boundaries of a single jurisdiction.
One of the defining characteristics of serial murder is the actuality of multiple victims over a period of time. Holmes and Holmes (1998) define serial murder as the killing of “three or more people over a period of more than thirty days, with a significant cooling-off period between killings.” The reference to the cooling off period serves to differentiate between other types of multicide, such as mass murder (bombings or school shootings), wherein many victims are claimed at one time and in one place, and spree murder, wherein the killings take place in a shorter period of time (and are often sequential rather than simultaneous) and usually in the presence of other felonies.
Another defining element of serial murder is related to the repetitive nature of the crime. Often a serial murderer’s “career” can continue on for years or even decades if his cycle is not interrupted. The murders are typically one on one, although there are incidences of more than one victim being dispatched in a single incident (although this is distinguished from mass or spree murder by the presence of other characteristics typical of serial murder.) There have also been numerous incidences of “team” killers (Faye and Ray Copeland, for example), murderers who killed with or in the company of others, (Holmes and Holmes.)
A third characteristic element of serial murder, one that seems to fuel the public’s sense of personal vulnerability, is the typically non-existent relationship between killer and victim prior to the crime. Serial murder seldom occurs between intimates, (Holmes and Holmes.) Rather, the victims of serial murderers are often strangers chosen specifically for an ideal victim type (IVT) which they represent (something possibly known or recognizable only to the killer.) Sometimes the victims may be acquaintances of the killer, but rarely do they ever have a closer relationship.
Another aspect of serial murder feeding the fear of the general population is the seemingly irrational nature of the crimes. Often the motives for the crime do not seem clear-cut or definable in the way society would expect. Simply put, the reasons for the murders are often known only to or understood only by the killer himself. The murders are generally not precipitated by the victim; that is, the victims do not contribute to or cause their victimization in any way (an opinion that could be argued by some in cases where victims are chosen based on high risk behaviors in which they engage, such as prostitution.) However, usually while the perpetrator might feel some clear sense of purpose or motive, that ‘motive’ is often intrinsic, coming from within the killer’s personality, and not seen as rational or sane by investigators or the general population.
While the number of murders actually committed by serial killers is unknown for a variety of reasons, according to the Bureau of Justice statistics, almost 30% of murders involve an unknown relationship between the killer and victim (Holmes and Holmes.) The extent of serial murder is unknown largely owing to the geographical transience of many of the criminals. This further complicates the accurate labeling of a killer as a ‘serial’ killer, due to the lack of information sharing across jurisdiction lines. However, some researchers suggest that there may be as many as 35 active serial killers at any given time in the United States. Although serial murder is by no means unique to the U.S., one global survey indicated that the U.S. has produced 76% of all known serial murderers in the 20th century, (Michael Newton, 2000.)
In actuality, although serial murder (and the depravity with which it is often accompanied) is seen as a new or growing trend in the U.S., there are references to such crimes in early American history, as well as the history of other countries. European countries boast such infamous names as Jack the Ripper, Gilles de Rais (who was active in the 1400’s and is said to have had victims numbering in the hundreds), and Elizabeth Bathory. In France and Germany there have been numerous occasions on which cannibal killers were prosecuted as “werewolves.” Early American history is marked by serial murder as well, some of the perpetrators well-known and even being canonized as American folk heroes in literature; William Bonney (Billy the Kid), Jeremiah Johnson, and Bill Longley are some examples. In the 1920’s, Earle Leonard Nelson terrorized landladies, raping and murdering 27 between February 1926 and June 1927, (Peter Vronsky.) Albert Fish and Ed Gein are notorious for their crimes in the first half of the 20th century. So it is clear that serial murder is not a new phenomenon.
Revisiting the idea of motive in relation to serial murder, the lack of apparent motive in serial murder is not only disturbing to the public, but is in fact another uniquely challenging aspect of investigating these crimes. What makes these killers tick? There are a few theories proposed to explain the serial murderer’s frame of mind. Although no clear clinical explanation for violent behavior exists, some research suggests that biological causes such as EEG abnormalities or head trauma could be to blame in some cases. However, this explanation does not account for the numerous people who have had physical trauma to the head and have never engaged in overtly violent behavior, nor the murderers studied who have no history of physiological or physical abnormalities.
Therefore, psychological and sociological theories have come to the forefront as predominant explanations for the violent behavior of serial murderers. While it is in some ways comforting to label these offenders as “psychos” because it seems to provide a rational explanation for their seemingly irrational and horrific crimes, true psychosis (temporary or permanent loss of touch with reality) is only the case in a very small percentage. The core ‘affliction’ of most serial killers is a personality disorder, Antisocial Personality Disorder (ASPD). These people might be referred to as psychopaths or sociopaths (terms that are sometimes used interchangeably++). A psychopath is not, however, psychotic. The core characteristic of sociopathology is the almost complete lack of empathy for others. A sociopath may also exhibit poor judgement, chronic lying, and inability to honor promises or commitments. (See DSM4-TR for full list of diagnostic characteristics.) In short, these individuals know the difference between right and wrong, they just don’t care.
So what causes a person to be a sociopath? There are extensive theories regarding this, but for the sake of brevity and simplicity, let us say that there are psychological and sociological theories that may help explain the development of a sociopath, including, but not limited to:
1) theories of social structure, wherein certain people are more prone to deviance and criminality
2) social process theories, whereby social learning concepts such as imitation and witnessing of violence during the formative years of childhood, and/or the occurrence of childhood abuse factor heavily, (Holmes and Holmes.)
Furthermore, many studies statistically link certain hallmark behaviors of ASPD which may be seen in developing children. They are known collectively as the MacDonald Triad and include cruelty to animals, obsession with fire-setting, and persistent bed-wetting in a child older than five.
While these theories are helpful focal points, it is essential to realize that there are different categories and types of serial murderers and for each type, their different characteristics are likely influenced by different contributing factors. For example, for general purposes, a serial killer may be said to be either intrinsically or extrinsically motivated.
As classified by Holmes and Holmes, male serial killers (there are slightly different categories for females, but since the majority of serial murderers are statistically men, we’ll examine those) may be grouped into four main groups. Briefly described, they are:
1) visionary- a psychotic individual often commanded to kill by voices or visions
2) mission-oriented – not psychotic, but has taken it upon himself to exterminate or eradicate a group of people he deems undesirable (ie. a woman he believes to be ‘loose’ or a prostitute)
3) hedonistic- an individual (not psychotic) who kills for personal gratification or pleasure (this category is divided into three further sub-types involving sexual and material motives)
4) power/control killer- this individual (not psychotic) derives satisfaction out of dominating and controlling the fate of the victim, enjoying the process of the murder, (Holmes and Holmes.)
In addition to the mindset and motives of each of these types of killers, the crime scenes and crime characteristics vary between the types. This may mean the difference in an organized crime scene and a chaotic one, or the difference between an abundance of evidence or hardly any. Some of these killers have an ideal victim type (IVT), while others choose victims out of convenience. Some types are geographically stable, while others are transient. WHY is all of this important in regards to the problem serial murder presents for law enforcement? All of these things impact the police’s ability to detect, identify, and apprehend these individuals and solve their cases. In short, these classifications and the differences they represent could give valuable insight into a serial killer’s personality and modus operandi, and therefore could be vital to the killer’s apprehension.
To sum up, serial murder is a unique crime and so presents a unique challenge to law enforcement in the U.S. and the world over. In order to appreciate the difficulties and special investigative styles involved in serial murder investigation, a working knowledge of the definition, history, and characteristic types is vital. Americans are fascinated and terrified by concept of serial murder, however much of their suppositions come from the media and popular fiction. It is the law enforcement agencies who must deal with the gruesome reality, and the reality seems to be that regardless of research and case studies on the topic, nothing is written in stone.
++EDIT (Some sources claim differences between the two in terms of certain personality traits; namely being that the sociopathic person tends to be more impulsive, hot-headed, and unable to maintain meaningful employment or interpersonal relationships, yet supposedly capable of a minute measure of empathy, whereas the psychopathic individual is considered to be calculating, charming, and without empathy, but quite adept at “faking” being normal.)