Do serial killers stem from genetic predispositions, environmental triggers or do these causes intersect to create violent behaviors? LILA Gazette dives deep into the fascinating roots of aggressive conducts.

By Julie Delloye – 9th grade.

The nature vs. nurture debate was first coined in the mid-1800s by English polymath Francis Galton, a cousin of Charles Darwin. This debate explores whether serial killers are created by inherited traits that consist of human traits, behaviors and personality or if they are shaped by the environment surrounding them. Understanding this question is essential to explaining human behavior and development. According to the FBI, a serial killer is an individual who has committed 3 murders over a time period of at least 3 years at 3 different locations with an emotional cooling off period in between. Therefore, the central question remains: do serial killers originate from genetic predispositions or rather environmental triggers?

Nature

The idea that serial killers may be “born” rather than made has long fascinated researchers. Some scientists believe biological factors such as genetics, brain structure and psychological disorders can cause violent behaviors. Because of this, many studies have examined whether biology could play a role in the development of serial killers.

Eric Hickey studied genetic patterns among 400 serial killers and found that 84% of them are male. This imbalance in gender in serial killers can be linked to hormones as men generally have higher testosterone levels than women, increasing impulsive and aggressive behaviors. This study also shows the average age of their first murder is 27.5 years. This may be caused by major life stressors such as job struggles, relationship issues and social isolation that take place in the late 20s. 

Moreover, experts have linked violent behaviors to mental conditions such as psychopathy and Antisocial Personality Disorder. These personality disorders are closely related, Antisocial Personality Disorder (ASPD) is defined by a long-term pattern of manipulating, exploiting or violating the rights of others without remorse by impulse. Meanwhile, psychopathy is often described as a more severe form of ASPD as individuals attained by this condition are often calm, calculated and can mask their intentions perfectly. The Forensic psychiatrist Michael Stone found that 91% of the 99 serial killers he examined were psychopaths. However, around 30% of the population is estimated to have low, medium or high levels of psychopathy. Therefore, this condition does not determine serial killers. Moreover, while only around 4% of Americans will meet criteria for an ASPD diagnosis at some point in their lives, around 86% of violent gang members meet the criteria for this disorder. Having a family member with ASPD increases the risk that it will show up on other family members with 20% of individuals diagnosed with ASPD having a close relative with the disorder. While not all individuals with these disorders are violent, they are heavily correlated with criminal behaviors and, under extreme conditions, with murder.

One serial killer often discussed in the “nature vs. nurture” debate is Edmund Kemper. He is an American serial killer born in Burbank, California in 1948, murdered his grandparents at age 15 and, after being paroled for that crime, killed 8 women from 1972 to 1973, including his mother. Ed Kemper is extremely tall, about 6’9” 

(2.06 m), his high stature made it easier for him to intimidate his victims. He also had unusually high levels of testosterone in his adolescence associated with increased aggression and dominance-seeking behavior. He presents abnormalities in areas of the brain linked to emotion and impulse control, especially the frontal lobe. The frontal lobe helps regulate decision-making and self-control. Abnormalities in this part of the brain can increase impulsivity, possibly leading to committing violent crimes without thinking them through. Criminologists consider Kemper a psychopath due to his lack of remorse after committing these crimes. He told District Attorney Chang: “One thing I learned at Atascadero was you don’t get far if you regret anything”. Therefore, serial killers can be born with genetic predispositions that lead to them committing these atrocious crimes. 

Nurture

However, many argue that serial killers are “made” and every human being is born inherently good with their environment leading them to committing these crimes. The nurture debate suggests that childhood trauma, abuse and violence are the primary drive that lead serial killers to committing murder. Because of this, experts have examined whether the environment you are born in can lead to violent behaviors.

Serial killers frequently have a history of physical or psychological childhood abuse. In a study by Radford University, fifty serial killers who murdered for the primary goal of sexual gratification, called lust killers, were studied to determine the prevalence of childhood abuse in murderers. The results of this study found that 68% of the killers have experienced some type of maltreatment, while only 32% of them were never confronted with any abuse. In contrast, in the general population, around 30% faced some type of abuse while 70% never experienced mistreatment. This difference shows that childhood abuse can be considered a primary source of dysfunctional relationships with others. In his book Serial Killers, Joel Norris describes the cycle of violence as generational: “Parents who abuse their children, physically as well as psychologically, instill in them an almost instinctive reliance upon violence as a first resort to any challenge.” Moreover, it is a possibility that the prevalence of abuse in serial killers’ lives is related to the desensitization of pain, depending on the frequency and the levels of the abuse. Childhood abuse has also been associated with later cognitive processing problems. In 1995, a study in the Journal of Abnormal Psychology of 584 randomly selected boys and girls from European American and African American backgrounds that experienced lifetime abuse. In this study, maltreatment was associated with later processing patterns such as encoding errors, the inability to effectively store or retrieve information in long-term memory. It showed that abuse shapes how individuals process social information, leading to conduct problems such as externalizing behaviors, actions turning internal conflicts outward. Childhood abuse has been proven to be a strong link in the development of serial killers leading to the habituation of pain, impeding the formation of healthy relationships with others and sometimes causing cognitive processing problems.

Another common issue found in many serial killers is the failure of early intervention by those surrounding them. Violent behaviors in the childhood of serial killers can often be spotted. The MacDonald triad, proposed by psychiatrist John MacDonald in 1963, posits that childhood enuresis (bed-wetting), animal cruelty and arson predict violent offenders. The report on 100 patients at the Colorado Psychopathic Hospital tested this theory. The patients varied in gender and ranged from age 11 to 83, with roughly half being categorized as psychotic, who had threatened violence. This study found that around 30% of them showed all three components while 60% only showed two components. 

Moreover, a study about the connection between animal cruelty and human violence found that 95% of serial killers abused animals. Animal cruelty is a valuable predictor of present and future violent behaviors as a learnt behavior from witnessing domestic abuse or to express frustration. Meanwhile, childhood enuresis is a main indicator of sexual abuse but it is also a typical part of child development. Furthermore, arson is another main indicator of psychotic behavior as the main reason for committing this crime is a need for power and control, similar reasons as committing multiple murders. Studies estimate around 51% of those who commit arson have antisocial personality disorder, which is also prevalent in serial killers. These early signs of violent behaviors could prevent the formation of dangerous predators if addressed early. Therefore, a lack of vigilance on these signs by the people surrounding the child can lead to serial killers. However, experts have doubted the validity of the theory as they have linked these characteristics to solely childhood trauma. 

Richard Ramirez, known as “The Night Stalker”, is a main character in the “Nature vs. Nurture” debate as he was heavily abused by his father during his childhood. Born in Texas, he was one of the most terrifying serial killers in American history. Between 1984 and 1985, he murdered at least 13 people randomly, brutally and sadistically, not targeting a specific type of victim. His father was a violent alcoholic who was subject to fits of anger, resulting in physical abuse towards his family members. Psychiatrist Michael Stone said that, at age five, he was knocked unconscious from a swing and he started experiencing epileptic attacks. At age twelve, Ramirez was fostered by his older cousin, Miguel Valles, himself a rapist and serial killer during his service in the Vietnamese War. He exposed Ramirez to images of rape and dismembered Vietnamese women, desensitizing him to these atrocities. By his teenagehood, Ramirez was addicted to drugs, using substances such as LSD and cocaine. These substance habits increased after he witnessed his cousin brutally murdering his wife. He began to hunt coyotes, rabbits and birds and would later mutilate them. Moreover, he committed theft and burglary to procure money to sustain his substance addiction. The escalation of these crimes led to him murdering multiple people, becoming one of the most notorious serial killers in American history.

Comprehending the reasons behind these horrific crimes can help reduce the murder rate by finding new strategies to catch serial killers. The evidence indicates that genetics play a key role in determining who becomes a serial killer. However, these predispositions commonly have to be accompanied with environmental factors such as childhood abuse and the precocious exposure to violence. As science evolves, advances in fields such as genetics and psychology may allow society to better identify risk factors and reduce the chances of individuals becoming serial killers.