Each serial killer is motivated to kill for different reasons: "Serial killers generally kill for one of several reasons, including personal pleasure, relief from stress or even to respect a personal set of moral or rational values” (Parker 9). The most common motivation for killing is the satisfaction serial killers feel from having complete control over their victims; therefore, victims are usually raped or tortured. Many serial killers even commit necrophilia on their victims. According to researchers from Bath Spa University and Cranfield University, serial killers satisfy their need for power by torturing their victims: "They often rape and kill their victims through mutilation – which gives them all a sexual gratification” (Taylor et al. 37). The deviant behavior that serial killers often exhibit is due to the need for autonomy over their own fate..