The term serial killer is widely believed to have been coined either by FBI agent Robert Ressler or by Dr. Robert D. Keppel in the 1970s (the credit for the term is disputed). Serial killer entered the popular vernacular in large part due to the well-publicized crimes of Ted Bundy (for whom the term was first used) and David Berkowitz (“Son of Sam”) in the middle years of that decade.
The term allows criminologists to distinguish those who kill several people over a long period of time from those who kill several people during a single event ( mass murderers ). A third type of multiple killer is a spree killer.
The following are brief definitions of these three types:
* A serial killer is someone who commits three or more murders over an extended period of time with cooling-off periods in between. In between their crimes, they appear to be quite normal, a state which Hervey Cleckley and Robert Hare call the “mask of sanity.” There is often - but not always - a sexual element to the murders. All the murders must be completed/attempted in a similar fashion or the victims must have something in common, ex. occupation, race, sex, etc.
* A mass murderer , on the other hand, is an individual who commits multiple murders in a single event and in one location. The perpetrators sometimes commit suicide , therefore knowledge of their state of mind and what triggers their actions is often left to speculation.
* A spree killer commits multiple murders in different locations over a period of time that may vary from a few hours to several days. Unlike serial killers, however, they do not take a long break and resume their everyday lives between slayings.
All of the above types of crimes are usually carried out by solitary individuals. There have been examples in all three categories in which two or more perpetrators have acted together.
There are other types of multiple killings as well, although they often involve larger organizations than two or three perpetrators: genocide and terrorist attacks .
The accepted stereotype of American serial killers is that they are disproportionately likely to be white and male, but there have been exceptions. Noted female serial killers include Aileen Wuornos , Myra Hindley , and Erzsébet Báthory .
The white male stereotype is very deceptive, however, since white males are less likely to be serial killers than male Hispanics or male blacks. African Americans make up 12 percent of the American population but 22% of serial killers and Hispanics roughly the same. Whites make up around 75% of the population but only 55% of all serial killers making whites proportionately less likely to be serial killers.
When caught and tried in a court of law in the United States, some serial killers will plead not guilty by reason of insanity . In most US jurisidictions, the legal definition of insanity is still generally based upon the classic common law “right or wrong” test delineated by an English court in the 1843 M’Naghten case. The M’Naghten rule , as it is generally known in the legal profession, hinges upon whether the defendant knows the difference between right and wrong at the time of the offense. With some serial killers, extensive premeditation, combined with lack of any obvious delusions or hallucinations that would hinder the defendant’s ability to elude detection after committing multiple murders make this defense extremely difficult and almost uniformly unsuccessful in achieving a not guilty verdict. However it does allow the defense to introduce evidence about the killer’s background which would normally be deemed inadmissible (for example a history of having received child abuse ) in hopes that some sympathy from the jury will spare the client a death sentence .
Serial killers frequently have extreme sadistic urges. Those who lack the ability to empathize with the suffering of others are frequently called psychopathic or sociopathic , terms which have been renamed among professional psychiatrists as antisocial personality disorder . Some serial killers engage in lust and torture murder , loosely defined terms involving, respectively, mutilation for sexual pleasure and killing victims slowly over a prolonged period of time.