Inside the mind of serial killers – are they born to kill?

By Luciano Marinelli

Serial killers have always intrigued society and have inspired multiple series and documentaries, providing valuable insights on their motivations and psychology. Are these individuals born to kill, or are they just victims of harsh circumstances? The psychology of serial killers, and its neuroscientific basis, has long been studied by psychologists and social scientists, and even though we are still far from the truth, many useful patterns have been identified which could help in our understanding of serial killers. This review will outline the underlying motivations of serial killers, particularly of those who are sexually motivated, as well as their neuroscientific basis.

Firstly, one of the main triggers that has been identified in most serial killers is childhood abuse and neglect from parents (Morono AJ et al., 2020), and research has shown strong correlation between early childhood abuse and individuals who kill for sexual gratification. A study by Mitchell H et al showed that on average 36% of serial killers experienced physical abuse, 26% experienced sexual abuse, and 50% experienced psychological abuse (Mitchell H. et al., 2005). However, how is this responsible for the violent impulses that motivate serial killers to rape and murder? It is thought that serial killers develop deviant sexual fantasies which involve sexual scenes in which they rape and humiliate women, and their actions are motivated by the anticipation of emotional reward the fantasies promise (Chassy P., 2017). Some develop such fantasies very early and may start practicing them on objects such as dolls. This may be the result of painful mental states arising from their childhood suffering, and it is hypothesised that it is a coping mechanism to temporarily escape from these painful abuse-related mental states in absence of alternative, less harmful ones (Maniglio R., 2011). These may be the trigger that allows these individuals to act on these fantasies rather than restraining from putting them into practice due to the ethical reasons and related potential consequences.

From a neuroscientific perspective, it is hypothesised that the neural networks that encode for the deviant sexual fantasies follow a certain, unique pattern of activation. One hypothesis that has been posited is the pathological neural watermark (PNW) hypothesis, which suggests that once a fantasy has been enacted, it becomes an autobiographical memory, which requires a specific pattern of activation, usually through exposure to a related item. This elicits an emotional response, also encoded by the PNW, which will activate such fantasy, which in turn causes sexual arousal, as shown by increased activity in the nucleus accumbens. This is the reason why investigators, during interviews, hold with them items that they know will elicit the fantasy in the suspect, hence make it more likely for him/her to show deviant behaviour (Mindhunter, 2017). Another component of the PNW codes the high level of aggression associated with the fantasy, both before and during its execution, and is determined by activity in the lateral hypothalamus as well as in prefrontal regions and the amygdala (Chassy P., 2017). 

While fantasies play a significant role in their motivations, they are just a part of a bigger picture which includes several other factors, among which the most relevant is the feeling of empowerment during the act. Their childhood of abuse and neglect makes them feel like misfits and powerless in society, which elicits in them feelings of both social and sexual inadequacy. The act of rape, in the words of the serial killer Ted Bundy, “gives you power over life and death” (Real Responders, 2020), a feeling of control they believe they lost in face of society. It also gives them feelings of sexual competence in order to hide their underlying sense of sexual inadequacy. In fact, as a demonstration of this, it is believed that serial killer Richard Speck raped his victims just as a statement of sexual competence (Mindhunter, 2017). In either case, it has been noticed that chosen victims are mostly middle class women, rather than alcohol- or drug-addicts, and this can be explained by the fact that they see women as lesser human beings and and want to tear down their image of niceness and pureness, which lower class women are not perceived to have (Real Responders, 2020). Such feeling of empowerment also explains why they seem to never be satisfied after each kill hence feel the impulse to kill more, since each kill eliminates the only witness of their power.

In light of this, studies have investigated the link between serial killers (and murderers in general) and psychopathy, since many of their behavioural traits align with those of individuals with psychopathic traits (McGreal S., 2018). Typical psychopathic traits include lack of remorse and empathy, impulsiveness, manipulative behaviour and grandiose sense of self (Martens WHJ, 2014). A meta-analysis was performed by Fox B et al. which analysed 22 studies of more than 2600 homicide offenders to assess their psychopathy levels. The psychopathy score of each offender was determined using the PCL-R system, and the average score was 21.1, which is relatively very high considering that the score from a normal person is around 5. Based on a psychopathy cut-off score of 25, 34% of offenders would be diagnosed as psychopaths, meaning it could be said that a third of offenders can be considered psychopathic. The study also found that those who committed more violent crimes, such as those involving sexual or sadistic elements, had higher scores. Overall, this study concluded that there is a significant correlation between psychopathy and criminal behaviour (Fox B. et al., 2019). 

Finally, to get a better undertanding of these concepts, the intriguing story of the notorious serial killer Ed Kemper is analysed. Ed Kemper experienced a difficult childhood, in line with the identified pattern, being emotionally and physically abused from his own divorced mother, Carnell, who frequently kept him locked in the basement. At the age of 14 he went looking for his father in hope of better treatment but, after being rejected from him too, went to live with his paternal grandparents. His grandmother was also very abusive and at the age of 15 he ended up killing her and then his grandfather in fear of his reaction. Between May 1972 and February 1973, he embarked on a series of six murders, in which he collected hitchhiking girls and transported them to a wooded area where he would kill them and rape the dead bodies. He would then decapitate the victims and engage in post-mortem sex with the dismembered heads (Bonn S., 2014). The fact that he engaged in sex only after murdering the victims is of considerable importance, as it highlights how engaging in post-mortem sex allowed him to restore his feeling of sexual inadequacy and impotence he felt when she was alive. He would also revisit the exact locations of his crimes to relive the sexual gratification he experienced and the feeling of complete dominance, total possession from a kill. This becomes a need which in turn becomes a compulsion (Mindhunter, 2017). 

Concluding, are serial killers born to kill or are they just victims of a harmful environment? While it is proven that the environment plays a significant role in the development of a serial killer, a genetic predisposition to violence should not be neglected. Ted Bundy, for instance, already exhibited abnormal behaviour at a very young age – at the age of 3 he was already interested in knives and in his teenage years he would continually spy on other people’s windows (Biography, 2014). Even though useful patterns have already emerged from ongoing research, there are still many questions that need to be answered. Hopefully, such knowledge and future insights may aid in the identification and profiling of serial killers to hopefully be able to predict their future actions.  


Biography. 2014. Ted Bundy – Victims, Family & Death. [online] Available at: [Accessed 29 June 2021].

Bonn, S., 2014. The Twisted Tale of “The Co-ed Killer”. [online] Psychology Today. Available at: [Accessed 26 June 2021].

Chassy, P., 2017. The neural signature of emotional memories in serial crimes. Medical Hypotheses, 108, pp.31-34.

Fox, B. and DeLisi, M., 2019. Psychopathic killers: A meta-analytic review of the psychopathy-homicide nexus. Aggression and Violent Behavior, 44, pp.67-79.

Maniglio, R., 2011. The role of childhood trauma, psychological problems, and coping in the development of deviant sexual fantasies in sexual offenders. Clinical Psychology Review, 31(5), pp.748-756.

Marono, A., Reid, S., Yaksic, E. and Keatley, D., 2020. A Behaviour Sequence Analysis of Serial Killers’ Lives: From Childhood Abuse to Methods of Murder. Psychiatry, Psychology and Law, 27(1), pp.126-137.

McGreal, S., 2018. Are Murderers Unfairly Labeled Psychopaths?. [online] Psychology Today. Available at: [Accessed 26 June 2021].

Mindhunter. 2017. [film] Directed by D. Fincher, C. Franklin, A. Douglas, A. Kapadia, T. Lindholm and A. Dominik. USA: Denver and Delilah Productions.

Mitchell, H. and Aamodt, M., 2005. The incidence of child abuse in serial killers. Journal of Police and Criminal Psychology, 20(1), pp.40-47.

Real Responders, 2020. Examining Ted Bundy’s Motivations | New Detectives Season | Real Responders. Available at: [Accessed 24 June 2021].

Willem H. J. Martens, P., 2014. The Hidden Suffering of the Psychopath. [online] Psychiatric Times. Available at: [Accessed 26 June 2021].

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