An investigation into sexual killing: considerations for assessment, understanding motivation and future research

Objective: This thesis reports an investigation into characteristics of sexual killers and their offences. Sexual killing was defined where there was a disclosure by the perpetrator that the killing had a sexual element, or there was evidence of sexual behaviour prior to or following the killing, or the victim’s clothes had been disturbed in a way that could not be explained by simply movement of the body. Consideration was given to perpetrators in terms of their childhood, adulthood, crimes and victim to understand better perpetrators of these crimes. Method: A template was developed to code the files of a sample of sexual killers for the presence or absence of items relevant to understanding perpetrators. Analysis of the data was undertaken to determine the characteristics of sexual killers. The data were examined to consider perpetrators who victimised a stranger, used a “hands-on” method of killing, disclosed fantasy, and were considered a loner at the time of the offence. Logistic regression analysis was carried out to identify variables that predicated an offender’s membership of these four groups. Results: Evidence was found to suggest that those perpetrators who victimise strangers are a distinct group, while perpetrators who use a “hands on” method of killing showed a more controlled killing with less excessive injury. In addition, perpetrators who disclosed fantasy experienced problems with parental and childhood social relationships and shared a number of characteristics with perpetrators who were considered loners. A developmental model of sexual killing based on the findings of this research was proposed. Conclusions: The findings supported previous research suggesting that being a loner is a characteristic of sexual killers and an indication that it is associated with those perpetrators who disclose fantasy. There was also a suggestion that the offences of sexual killers who victimise strangers are driven by sexual motivation and that strangulation itself is sexually significant. Future assessment of sexual killers should focus upon factors identified in this study to inform treatment and also consider the possible implications for risk assessment. Steps towards validation of the model proposed in this study will help with further understanding the development and motivation of sexual killers.