Dennis Andrew Nilsen was a Scottish serial killer and necrophile who murdered at least twelve young men and boys between 1978 and 1983. Convicted at the Old Bailey of six counts of murder and two of attempted murder, Nilsen was sentenced to life imprisonment on 4 November 1983, with a recommendation that he serve a minimum of 25 years; this recommendation was later changed to a whole life tariff in December 1994. In his later years, Nilsen was imprisoned at HM Prison Full Sutton in the East Riding of Yorkshire.

A serial killer is a person who murders three or more people, with the killings taking place over a significant period of time between them. The serial killers' psychological gratification is the motivation for the killings, and many serial murders involve sexual contact with the victims at different points during the murder process. The Federal Bureau of Investigation (FBI) states that the motives of serial killers can include anger, thrill-seeking, financial gain, and attention seeking, and killings may be executed as such. The victims tend to have things in common such as, demographic profile, appearance, gender or race. The FBI will focus on particular patterns that the serial killers follow throughout their murders. They will then use on the patterns they find for key clues into finding the killer along with their motives. Although a serial killer is a distinct classification that differs from that of a mass murderer, spree killer, or contract killer, there are overlaps between them.