Serial Killer

A serial killer is traditionally defined as an individual who has killed three or more people over a period of more than a month, with down time (a "cooling off period") between the murders, and whose motivation for killing is usually based on psychological gratification. Some sources, such as the FBI, disregard the "three or more" criteria and define the term as "a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone" or, including the vital characteristics, a minimum of two murders. Often, a sexual element is involved in the killings, but the FBI states that motives for serial murder include "anger, thrill, financial gain, and attention seeking". The murders may have been attempted or completed in a similar fashion and the victims may have had something in common; for example, occupation, race, appearance, sex, or age group.

Serial killers are not the same as mass murderers, nor are they spree killers, who commit murders in two or more locations with virtually no break in between; however, cases of extended bouts of sequential killings over periods of weeks or months with no apparent "cooling off" period or "return to normalcy" have caused some serial killer experts to suggest a hybrid category of "spree-serial killer".