What causes a person to become a serial killer? Are people meant to become murderers, or do events from their childhood shape their adult choices? The question of nature verses nurture in terms of serial killer development has long been debated upon among different fields, particularly in psychology. Television shows such as Criminal Minds and Dexter have introduced serial killers to the world in a way that has sparked interest and demonstrated the different influences that can lead to the creation of someone who continuously kills others with seemingly no remorse. Are people born to kill and have no choice in the matter, or are serial killers made depending on their circumstances? A combination of genetic and environmental factors, such as genetic mutations, chemical imbalances, and abusive upbringings consisting of physical, emotional, and sexual abuse come into play in the making of serial killer.  In their book How to Make a Serial Killer: The Twisted Development of Innocent children into the World’s Most Sadistic Murderers, Christopher Berry-Dee and Steven Morris looked at past research and conducted their own on children and convicted serial killers’ pasts to prove that a person’s genetics and upbringing both contribute to who they become. A team of researchers in Dunedin, New Zealand studied the MAOA gene, which aids in the breakdown of neurotransmitters linked to mood, aggression, and pleasure, in 1,037 children. It is possible to have either a weak or strong variant of this gene. Of the male children found to have the weak variant of the gene and to have been abused, 85% exhibited criminal or antisocial behavior. This rate was nine times greater than males who had been abused but were found to have the strong variant of the MAOA gene. An example of a serial killer with this condition is Michael Ross, a psychopath who raped and murdered eight women. He was not only physically and possibly sexully abused as a child, but also had the weak variant of the MAOA gene.

Another serial killer, Arthur Shawcross, was found to have a rare XYY genetic disorder which could be behind his desire to murder people. Males with this disorder are more likely to have learning and behavioral disabilities and to be described as problem children.  Shawcross was also found to have a biochemical imbalance caused by having an excessive amount of the chemical kryptopyrrole in his body. Kryptopyrrole originates from Greek and Latin and means “hidden fiery oil.” Its chemical structure is similar to chemicals that are known to be toxic, like LSD. This biochemical is normally found in people in small amounts or not found at all, yet Shawcross’s reading was ten times higher than the average. This disproportionate amount of kryptopyrrole is linked to anger, mood swings, and noise and light sensitivity. People with this condition may also be dangerous to the public. These are all characteristics which fit Shawcross. While these genetic factors predispose a person to violence later in life, upbringing seems to have played an even larger role in the lives of those who have become serial killers. (Berry-Dee 7-14)

A person with psychopathy is a good example of someone who may be triggered by their surroundings. According to research conducted on the brain, psychopaths are believed to have a dysfunctional amygdala, which is the part of the brain that processes fear. Their inability to feel fear or sense it in others is thought to be the reason that some psychopaths are able to murder people in such a sadistic way. They are not afraid of being caught, nor are they sympathetic to the fear of their victims. While not all psychopaths are serial killers, most serial killers are psychopaths who share certain characteristics. Signs of a psychopath include someone who engages in violent and risky behavior without fear, has affairs or engages in promiscuous behavior, can charm and manipulate others, and does not take responsibility for actions. A person may have these antisocial tendencies and be a verifiable psychopath, yet never murder anyone. The theory for this is that an individual who has these genetic factors will only become violent when triggered by their environment. Someone who suffers physical, emotional, or sexual abuse during childhood is more likely to become a serial killer than someone who did not.  James Fallon, a neuroscientist and teacher at the University of California, is an example of a man who has a genetic predisposition to violent tendencies but never acted on them. He had a supportive family growing up and was never abused as a child, which is believed to be the distinction between people like him and those who grow up to become serial killers. Disorders such as this may be the cause of antisocial tendencies leading to serial killing, but it is environmental influences that typically trigger a negative response. With the proper upbringing, a person with a genetic predisposition, such as Fallon, may grow up to be perfectly healthy.

Arthur Shawcross, however, does not appear to be so lucky. He claimed he was abused both physically and sexually as a child, which likely led him to become a serial killer. As mentioned above, Shawcross had an XYY genetic disorder and a high amount of kryptopyrrole, in his body. He is also a psychopath. It is probable that these genetic disorders were set off by the abuse he endured as a child, causing him to commit multiple murders. In the documentary “Interview With A Serial Killer” on the YouTube channel Real Stories, Arthur Shawcross was interviewed by a psychiatrist and described the sexual abuse he was subjected to as a child. His doctor and psychiatrist both believe that his brain was different from other peoples’ because of his genetic conditions and that these conditions were triggered by the abuse he went through. His psychiatrist also stated that lesions on his brain caused him to have seizures so he may have been unable to remember some of the murders he had committed. Although none of this justifies the murders he committed, it does offer insight into the experiences that led him to do so.

Multiple studies were conducted by C. S. Alley and recorded in “Neurodevelopmental and Psychosocial Risk Factors in Serial Killers and Mass Murderers” confirming the theory that upbringing can trigger genetic disorders. In a study of 62 male serial killers, 42% had been rejected by people that were important to them. It was also found that children who were abused or neglected were three times more likely to become violent than those who had not. In an adoption study, 40% of the children would become criminals if they had a genetic predisposition to violence and both their biological and adoptive parents were abusive, whereas only 12% would become criminals if they contained the genetic disposition but were not abused. Only 6.7% would become criminals if they were only abused and did not possess a genetic predisposition. This research shows that a combination of genetics and abuse are most likely to result in a violent criminal. Laurence Miller also wrote in Serial Killers: II. Development, Dynamics, and Forensics that many serial killers were illegitimate or adopted children, with some being sons of prostitutes. “Many were severely abused physically and sexually as children, and a number have had intensely ambivalent, smothering relationships with their mothers that were characterized by both maternal abuse and sexual attraction to the mother.” (Miller 2.1) 

Although genetics and environment are typically the causes of a person becoming a serial killer, these influences often manifest themselves in different ways. In her book Inside the Minds of Serial Killers, Katherine Ramsland discusses different motivations individual serial killers have as a result of genetic disorders and unstable environments. Edmund Kemper III was convicted of murdering at least eight women. As a child, he had exhibited psychopathic tendencies and been abused by his mother. These issues caused him to have a great deal of anger.  It was this rage that led him to murder several women and eventually kill his own mother (Ramsland 71-72).

Charles Cullen was a nurse who had had a difficult childhood. Both of his parents died by the time he reached high school, and then two of his siblings died. He had been married, but it ended in divorce. Nurses often do not feel like they are appreciated, especially male nurses. A combination of his childhood and feelings of being undervalued is likely the reason he killed between 30 and 40 patients. He claimed that he killed his patients to end their suffering, and it is also suspected he wanted to feel a sense of power and control that he had not been able to have over his own life (Ramsland 155).

English serial killer Colin Ireland was driven by his desire for acknowledgement and fame. He wanted the police to know that the same person was responsible for killing all of the victims, which he had lured from gay bars. It was also important to him to be written about in papers because he wanted credit for his crimes. and He killed five men, each time leaving messages for the police to ensure they knew that his murders were committed by the same serial killer. As a child, Ireland’s father left him and his mother. His mother moved around frequently, eventually leaving Ireland in a children’s home until she remarried and could take care of him.  Throughout his childhood, he was harassed by several male pedophiles. He was never sexually abused, but as he was continuously offered money for favors by these pedophiles, he likely began to associate pedophilia with gay men, leading him to select his victims from gay bars. The reasoning behind his desire for fame and glory is not verified, but may have stemmed from his childhood of moving around and being the target of bullying (Crime and Investigation).

Several other motivations were mentioned by Laurence Miller in Serial Killers: I.  Subtypes, Patterns, and Motives. He listed several categorizations of serial killers, the first being psychopathic sexual sadists, also called lust murderers. This type of serial murderer handles and kills their victims in a sexual way for a thrill. There are psychotic killers, under delusions that they are defending themselves or have been called by a higher being to murder certain people groups. The power-seeking serial killer enjoys killing people because it gives them a sense of domination over their victims. They may have been abused and felt a sense of helplessness as a child and now feel the need to take control of others. They may also have a hatred for “weak” women and have a desire to put them in their place. 

Although not as prevalent as male serial killers, female serial killers exist and tend to have different motivations behind their murders. Females will often kill because they are seeking power, but for a different reason than males. It is likely the result of a traumatic experience such as rape, creating the need to control others instead of being controlled. Female serial killers also murder under the command of partners, family members, or cult leaders. These women may go through with murder to please others and receive approval rather than because they want to kill people. This may originate from abandonment as a child. They do not want the person to leave them, so they obey any requests asked of them, even if that means committing murder. There are also instances where the female partner enjoys killing as much as her male counterpart. In these cases, the couple will often rape and kill the victims together because they both get a thrill from it.

Scientists have been conducting research on the lives and minds of serial killers for years in an attempt to understand and classify their motivations, yet there is still much to learn. Serial killers’ genetic differences combined with their childhood environments lead them to become callous murderers, but there may be ways to prevent this from happening. Considering the possibility that people with these genetic disorders, chemical imbalances, and mental illnesses can be triggered by traumatic experiences that would cause them to commit murders to we should continue to seek solutions that will ensure their own safety, as well as the community’s. 
