A serial killer is a person who murders two or more people in separate events, usually for abnormal psychological gratification, thrill-seeking, attention, or financial gain. The FBI differentiates serial killing from mass murder or spree killing by the presence of a cooling-off period between victims. For this reason, mass murderers, such as school shooters and suicide bombers, are not included under the umbrella of serial killers. Serial murders are further defined as those committed by one or two individuals, excluding instances where groups are responsible for deaths.
Serial killings are rare, accounting for less than 1% of total homicides. In the United States, serial killing was at its highest in the period between 1970 and 2000, when 70% of recorded serial murders occurred. Rates of serial killings have been on the decline since the 1990s.
While serial killers are not solely a U.S. phenomenon, the majority of serial killers on record have operated at least in part in the United States. Serial murderers tend to be lone, white males.
Most serial killers kill for financial gain or enjoyment, with 32% on record stating they killed for financial gain and a quarter claiming to have killed for pleasure. Anger is cited as the primary motivator for another 18% of serial murders, and gang activity accounts for 6%.
Serial killers often have a preferred killing method and victim type. Ted Bundy, for example, targeted attractive, college-aged females and used strangulation as his primary method of killing. Shooting is the most common killing method among serial killers, followed by strangulation and stabbing. Serial killer victims are evenly split between males and females, and the median age of victims is 30.
The United States had more serial killers than any other country. A total of 12,236 victims of serial killings were registered nationwide between 1990 and 2020. California has the highest number of serial killings with 1,777 total, followed by Texas with 984. However, due to varied population sizes, these totals do not reflect the states where serial killing is most common. Washington DC has the highest rate of serial killings, with 25 victims per 100,000 residents. Alaska has the second-highest rate at 7 per 100,000; Louisiana comes in third with 6.5 serial killings per 100,000.
All 50 states have had a notorious serial killer, such as Florida's Ted Bundy, Illinois's John Wayne Gacy, and New Jersey's Charles Edmund Cullen.