Serial Killer Definition

Like certain other terms—obscenity, for example—serial killing is surprisingly tricky to define. Part of the problem is that police definitions tend to differ from popular conceptions. According to some experts, a serial killer is any murderer who commits more than one random slaying with a break between the crimes. There is certainly some validity to this viewpoint. If (for example) Ted Bundy had been caught after committing only a couple of atrocities, he wouldn’t have gained worldwide notoriety—but he still would have been what he was: a demented personality capable of the most depraved acts of violence. Still, it’s hard to think of someone as a serial killer unless he’s killed a whole string of victims.

How many victims constitute a “string”? Again, it’s hard to be precise. The most infamous serial killers—Bundy, Gacy, Dahmer, etc.—are the ones responsible for double-digit murders. Most experts seem to agree, however, that to qualify as a serial killer, an individual has to slay a minimum of three unrelated victims.
The notion of a string implies something else besides sheer number. A serial killer must perpetrate a number of random killings with an emotional “cooling-off” period between each crime. This hiatus—which can last anywhere from hours to years—is what distinguishes the serial killer from the Mass Murderer, the homicidal nut who erupts in an explosion of insane violence, killing a whole group of people all at once. Thus, the official FBI definition of serial homicide is “three or more separate events with an emotional cooling-off period between homicides, each murder taking place at a different location.”
There are several problems with this definition, however. For one thing, not all serial killers commit their murders in different locations. The nearly three dozen victims of John Wayne Gacy, for example, all met their horrible deaths in the basement of his suburban ranch house. And there are murderers who commit three or more separate homicides over extended periods of time who aren’t serial killers: mob hitmen, for example.
What distinguishes a professional hitman from a serial killer, however, is that one kills for money—it’s his job—while the other kills purely for depraved pleasure. A hitman may enjoy his work, but murder isn’t his primary source of sexual gratification. The situation is different with psychos like Gacy, who reach the heights of ecstasy while perpetrating their atrocities. According to many experts, in other words, true serial killer always involves an element of unspeakable sexual Sadism.

Taking these issues into account, the National Institute of Justice offers a definition we find more useful than the FBI’s: “A series of two or more murders, committed as separate events, usually but not always committed 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.”