The most critical factor common to serial killers is violent fantasy. Prentky and colleagues (1986), who studied repetitive sexual homicides, found that daydreams of causing bodily harm through sadism and other methods of sexual violence were common among offenders. The researchers concluded that the offender attempts to replicate his fantasies. Since the offender can actually never be in total control of his or her victim’s responses, the outcome of the fantasy will never measure up to his or her expectations. In any case, each new murder provides new fantasies that can fuel future homicides. Ressler and his colleagues (1988) concluded that ‘sexual murder is based on fantasy’(p.33). Fantasy becomes a critical component in the psychological development of a serial killer. Although fantasies are generally associated with sexual homicides, they are likely to be found in the minds of most, if not all, serial killers.