I actually think I may be possessed with demons, I was dropped on my head as a kid.

— Dennis Rader
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Serial Killers Introduction


Serial murder is neither a new phenomenon, nor is it uniquely American. Dating back to ancient times, serial murderers have been chronicled around the world. One reason people tend to think that serial murder is a frighteningly new phenomenon is that, until about twenty years ago, no one ever heard of such a thing. For most of the twentieth century, the news media never referred to serial killers. But that isn’t because homicidal psychos didn’t exist in the past. Serial murder is a relatively rare event, estimated to comprise less than one percent of all murders committed in any given year. However, there is a macabre interest in the topic that far exceeds its scope and has generated countless articles, books, and movies.

The origin of the term “serial killer”

Credit for coining the phrase “serial killer” is commonly given to former FBI Special Agent Robert Ressler, one of the founding members of the Bureau’s elite Behavioral Science Unit (aka the “Mind Hunters” or the “Psyche Squad”).
In his 1992 memoir,Whoever Fights Monsters, Ressler writes that, in the early 1970s, while attending a weeklong conference at the British police academy, he heard a fellow participant refer to “crimes in series,” meaning “a series of rapes, burglaries, arsons, or murders.” Ressler was so impressed by the phrase that, upon returning to Quantico, he began to use the term “serial killer” in his own lectures to describe “the killing of those who do one murder, then another and another in a fairly repetitive way.” However, there is a problem with this story, since there is a documented proof that this expression existed at least a dozen years before Ressler supposedly invented it.
First documented use of this term is traced back to 1961, and is used in Merriam Webster’s 1961 Third New International Dictionary. However, it was Ressler who altered the phase from serial murderer to serial killer.

Defining a phrase “serial killer”

Even though, a phrase serial killer was invented to describe a specific type of criminal activity, there is no clear definition.
In the past thirty years, multiple definitions of serial murder have been used by law enforcement, clinicians, academia, and researchers. While these definitions do share several common themes, they differ on specific requirements, such as the number of murders involved, the types of motivation, and the temporal aspects of the murders.

Most of the definitions also required a period of time between the murders. This break-in-time was necessary to distinguish between a mass murder and a serial murder. Serial murder required a temporal separation between the different murders, which was described as: separate occasions, cooling-off period, and emotional cooling-off period.

Here is the official FBI definition, taken from the FBI Crime Classification Manual from 1992:

Three or more separate events in three or more separate locations with an emotional cooling-off period between homicides.

This definition stresses three important elements:

  1. Quantity. There have to be at least three murders.
  2. Place. The murders have to occur at different locations
  3. Time. There has to be a “cooling-off period”-an interval between the murders that can last anywhere from several hours to several years.

However, there are several problems with this FBI definition – it’s too broad and overly narrow. These flaws are rectified in another, more flexible one formulated by the National Institutes of Justice, which many authorities regard as a more accurate description:

A series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone. The crimes may occur over a period of time ranging from hours to years. Quite often the motive is psychological, and the offender’s behavior and the physical evidence observed at the crime scenes will reflect sadistic, sexual overtones.

-National Institutes of Justice