A serial killer is typically a person who murders three or more people, with the murders taking place over more than a month and including a significant period of time between them.[1][2] The Federal Bureau of Investigation (FBI) defines serial killing as "a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone".[3][4]
Serial murder is the killing of three or more people over a period of more than 30 days, with a significant cooling-off period between the murders [...] The baseline number of three victims appears to be most common among those who are the academic authorities in the field. The time frame also appears to be an agreed-upon component of the definition.