Serial killings involve the premeditated murder of individuals over a period of years, a time in which the perpetrator may target victims with similar physical and social characteristics. Often the nature of the violence inflicted is reflective of the serial killer's particular psychosis and social background. Many serial killers have been linked to histories of parental sexual, emotional and physical abuse, and believe that society benefits from the deaths of their victims.
A 1991 study by one US psychologist suggested that serial killers tend to be intelligent, often have an impairment of the central nervous system (from epilepsy to dyslexia), tend to be fascinated by fire, and report fantasies of murder and mutilation. The study found that 1 in 3 serial killers experiment with cannibalism.