Despite endless research being conducted within this area of study, researchers still struggle with determining the cause of serial killers. Thus, the main question is: are serial killers born or made? As previously stated, researchers have identified a series of biological predispositions related to these groups of people. In fact, since the beginning of time, it has been believed that criminals were born – not made. Dating back to the 19th century, Lombroso examined the phenotypes of Italian criminals in order to determine whether criminal characteristics could be passed down from generations. He hypothesized that criminals were born callous and cruel while lacking remorse. Lombroso also mentioned that these individuals tended to be antisocial. Although, many of these theories have been disproven by modern research, researchers have admitted to some underlying truth from outdated studies. Take Lombroso’s experiment for example, he was able to distinguish a hereditary link between future violent behaviors. Interestingly enough, genetics accounts for approximately 40-60% of antisocial and aggressive behaviors. According to adoptive studies, there is a 12.1% chance that a child will develop violent tendencies, if their biological parent is violent. Jeffrey Landrigan is a perfect example of this. Landrigan was put up for adoption when he was born. Growing up he exhibited several delinquent behaviors. At the age of 20 Landrigan murdered his first victim. By the age of 25 Landrigan had killed two people and was sentenced to death. While in prison, it was discovered that Landrigan was related to another inmate, Darrel Hill, who was his father. Like his father, Landrigan had abused drugs and committed murder twice. It was also discovered that Landrigan came from a family of crime where his grandfather and great-grandfather were both criminals as well. Landrigan’s story and many others like his are important for developing a greater understanding of crime and serial killers at large by examining the correlations between genetics and violent behaviors. To reference the statistics above, genetics can play a significant role in an individual’s future, specifically their likelihood of becoming an offender. This is a crucial piece of information for various reasons. It not only allows for a greater comprehension as to why an individual may engage in brutal crime, but more importantly the research suggests that regardless of race, gender or social class genetics has a universal effect on the outcome of human beings.
Despite from having a family history of crime, serial killers often suffer from a series of disorders. Out of 57 adolescents accused of homicide, 64% were found to have developmental problems with regards to disruptive behaviors, such as conduct disorder, attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder. Recent studies have found that violent offenders were commonly diagnosed with a neuropsychiatric disorder within their childhood and were often said to be associated with their criminality. Those diagnosed with conduct disorder displayed a decrease in prosocial behavior and physiological responses in stressful situations as well as an increase in psychopathic tendencies. These individuals were less likely to help and feel sympathetic towards others, causing them to react poorly in emotionally stimulating events. Due to these individuals’ lack of awareness of others’ emotions, their interpersonal relationships were negatively impacted. As a result, it is common for these individuals to engage in antisocial behaviors which have been linked to adult crime. Despite the small population, similar results were found for offenders diagnosed with ASD. It was said that these individuals had difficulty understanding and processing non-verbal communications. It is because of this that offenders are unable to develop strong relationships with their peers, causing them to become socially isolated and incapable of fully understanding the effects of their actions on others. Thus, it is not abnormal for these individuals to engage in more brutal crimes.
According to Loana (2013), individuals with Klinefeleter’s syndrome (KS) are five times more likely to become a serial killer when compared to the general public. KS is a chromosomal mutation, which causes an extra sex chromosome (X) to be located in men. A similar disease has been discovered, where an additional Y chromosome appears in the individual’s biological makeup. This has been deemed as the “crime chromosome”, as the frequency among criminals is 10 times higher than that of the general population. A nationwide study confirms this ideology after investigating the criminal patterns of males between the ages of 15 and 70 diagnosed with KS and XYY. It was found that men with an extra sex chromosome were more likely to be convicted when compared to the general public. A significant increase was discovered in offenders of sexual abuse, burglary, arson and ‘other’ convictions. It is believed that these high rates of convictions are due to low IQ levels and poor socioeconomic status. It is common for men diagnosed with these diseases to experience additional psychiatric disorders, psychophysiological dysfunctions and/or increased sexual deviation. These sexual deviations are believed to be due to the confusion attached to these individuals’ sexuality and inability to distinguish socially and legally accepted behaviors; explaining the high levels of sexual abuse convictions among these folks.
Brain Regions and Chemical imbalances
The brain is a complex and organized structure that controls the way humans think and behave. It is separated into two parts: the left and right hemispheres; functioning bilaterally. A crossover of information occurs and is dominated by either the left or right hemispheres. Resulting in the left side of the body being controlled by the right hemisphere and vice versa. It is important to note that the brain is dependent on localization; meaning, each region has its own specific function(s). Thus, damage to a region may result in specific behavioral outcomes. These outcomes are typically noted as dysfunctions, as the individual is unable to produce the same behaviors as a typically healthy person within the same environment and situations.
In recent studies, a strong positive correlation between serial killers and head trauma has been discovered, where an increase in violent behaviors are believed to be exhibited after trauma. This can either occur during birth or from an unfortunate event, such as a fall or hit to the head. Take Robert Long for example, after being in a motorcycle accident and suffering a head injury. An increase in violent behaviors occurred, which lead to the engagement of violent crimes. It was said that Long suffered damage to the left temporal lobe. Located in the temporal lobe is the limbic system, which is famously known for its involvement in human emotion. Dysfunctions to the limbic system, specially the hypothalamus can cause hormonal and neurotransmitter imbalances resulting in a lack of prosocial behaviors and an increase in aggressive and violent acts. Serotonin is a neurotransmitter that is commonly known for its regulation in mood, specifically happiness. It has been found that serotonin is widely associated with violent behaviors. According to a series of studies, serotonin is a chemical that can subdue aggression. Therefore, low levels of the neurotransmitter have been linked to an increase in aggression, impulsivity and self-destructive violence. In addition, dopamine and norepinephrine has also been linked to aggression and a number of disorders, such as ADHD, schizophrenia and ASD. However, the most common hormone believed to be correlated with violent tendencies and adult crime is the male sex hormone, testosterone. According to these studies, high levels of the testosterone increases aggression and violent tendencies, suggesting that convicted offenders have low levels of monoamine oxidase A – an enzyme that metabolizes several hormones and neurotransmitters – causing an increase in dopamine, norepinephrine and testosterone, leading to future offending.
Additionally, the amygdala is a structure located in the limbic system that controls fear responses. Individuals suffering from damage to this part of the brain is said to exhibit low emotional intelligence. As a result, these individuals are incapable of determining, expressing and understanding their own emotions as well as the emotions of others. Resulting in a decrease in interpersonal relationships and the increase of antisocial behaviors as well as delinquency and violence, which has been linked to adult criminality. Adults with psychopathic traits were more likely to experience blunter emotion responses when the amygdala was damaged; therefore, resulting in more focused aggression and brutal crime.
Similar results have been discovered when damage to the frontal lobe has occurred and has been said the be very common among serial killers. Considering the frontal lobe is widely involved in motor and higher cognitive functions, such as memory, problem solving, impulse control, and social and sexual behaviors, it is not surprising that lesions to this area of the brain can cause significant changes in one’s personality. In fact, a widely known case of personality change after head trauma is Phineas Gage. Although Gage did not experience any violent tendencies, he did become more aggressive and many said that he was “no longer Gage”. Ultimately displaying the significant impacts head trauma has on an individual’s defining traits. According to Glenn and Raine (2014) antisocial and violent behaviors are best correlated with frontal lobe dysfunction, exhibiting an increase in aggression and impairments in inhibitory control and emotion processing. This has been said to be the explanation behind why an offender may engage in cruel acts as well as why they may not respond logically to their actions or stressful situations.