A serial killer is typically a person who kills 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 murder as "a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone".[2][3]
The United States has by far the largest number of documented serial killers in the world. According to Radford University's Serial Killer Information Center, it has more documented serial killers than the next ten highest countries on the list.[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.