serial murder, also called serial killing, the unlawful homicide of at least two people carried out by the same person (or persons) in separate events occurring at different times. Although this definition is widely accepted, the crime is not formally recognized in any legal code, including that of the United States. Serial murder is distinguished from mass murder, in which several victims are murdered at the same time and place.
There has been considerable debate among criminologists about the proper definition of serial murder. The term serial murder was popularized in the 1970s by Robert Ressler, an investigator with the