Do serial killers have a certain gene? (3 insights)

This blog post aims to answer the question, “Do serial killers have a certain gene?” and study who serial killers are, how their brains work, their traits, functionalities and their genetic composition in order to help understand the answer. 

Do serial killers have a certain gene?

Yes, many serial killers have a certain gene that makes them the way they are. MAOA and CHD13 are referred to as “serial killer genes” by some. The following are 3 insights about the serial killer genes –  

  • Genetic susceptibility test.
  • SCL6A4 and HTR2B.
  • MAOA and CDH13.

These 3 insights about the serial killer genes will be discussed in further detail below after taking a deeper look at who a serial killer is. 

Who is a serial killer? 

A serial killer is someone who murders three or more people, generally for abnormal psychological enjoyment, over a period of more than a month and with a large gap between them. While the majority of authorities establish a three-murder threshold, others raise it to four or lower it to two.

The most common reason for serial killing is psychological fulfilment, and many serial killings involve sexual interaction with the victim, but serial murderers’ motives can also include rage, thrill-seeking, financial gain, and attention-seeking, according to the FBI.

In a similar way, the murders may be attempted or completed. The victims may share characteristics such as demographic profile, appearance, gender, or ethnicity.

The FBI frequently focuses on a certain pattern that serial killers follow. Based on this pattern, vital clues about the killer’s identity and intentions will be revealed.

Despite the fact that a serial killer is a different categorization from a mass murderer, spree killer, or contract killer, there are conceptual parallels between the three. 

There is some disagreement over the precise requirements for each group, particularly when it comes to the distinction between spree and serial killers.

Types Of Serial Killers.

Although it is hard to fully categorise and comprehend each serial murderer, it is possible to examine their tactics and habits in order to better characterise the sort of criminal they are. 

The Federal Bureau of Investigation has classified serial murderers into three categories based on how they commit their crimes. Knowing which group a serial killer belongs to can help investigators better understand their crimes and how to bring them to justice.

The Medical Killer.

Despite the fact that this sort of killer is extremely rare, certain people have used the medical field to carry out their evil crimes. Because it is not commonplace for individuals to pass away at a hospital, this sort of murderer believes they are shrouded. 

They are typically knowledgeable people who know how to cover their crimes with care and deception. If a person looks to have died of natural causes, there will be no reason to assume foul play and seek for the perpetrator. 

Only a few physicians in history have been able to kill scores of individuals before others notice.

The Organized Killer.

This is the most difficult sort of serial murderer to track down and apprehend. They are typically clever and extremely well organised, almost to the point of being fastidious. 

Every element of the crime is meticulously planned, and the assailant takes every measure to ensure that no damning evidence is left behind. This sort of psychopath is known to observe potential victims for several days in order to select someone they perceive to be a good target. 

Once the victim has been picked, the murderer would abduct them, frequently using a ruse to win sympathy, and transport them to a new place where the murder will be carried out. When someone is killed, the offender will generally take steps to ensure that the body is not discovered until they want it to be.

A criminal like this is generally quite proud of what they regard to be their “job” and pays close attention to news headlines about their crimes. One of their motivational motivations may be to elude the cops who are attempting to solve their crime.

The Disorganized Killer.

These people almost never plot their victims’ deaths in any way. The victims they kill are almost always in the wrong place at the wrong time. 

When the chance arises, this sort of serial murderer appears to strike at random. They make no attempt to hide their crime and move around often to avoid getting apprehended. 

Killers who are disorganised frequently have low IQs and are antisocial. They don’t have many close friends or family members, and they don’t like to stay in one area for lengthy periods of time. 

These assassins are more likely to have no remembrance of their crimes or to admit that they were driven by voices in their brains or some other fictitious source.

What are these 3 insights about the serial killer genes?

Genetic susceptibility test.

In 2010, an Italian court made legal history when he cut the already reduced sentence of a male criminal guilty of murder after the offender was shown to be a carrier of genetic variations associated with a proclivity for violence (Forzano et al., 2010).

Prior to this intervention, the convict’s sentence had been lowered since he had schizophrenia and was actively insane at the time of the crime. 

The defence was authorised to undertake a ‘genetic susceptibility test’ at the appeals court, which revealed that the prisoner had particular variations for the MAOA, COMT, SCL6A4, and DRD4 genes that have been linked to aggressiveness modulation, resulting in a reduced sentence from 9 to 8 years.

The aetiology (the collection of causes and mode of production of a disease or condition) of violence has long piqued the interest of behavioural psychology as a topic. 

The historic Italian sentencing occurred at a time when the social landscape was rife with studies linking genetics to a predisposition to violence, aggression, impulsivity, and other behaviours, as well as how such effects were compounded by environmental factors like substance abuse and childhood malnutrition.

SCL6A4 and HTR2B.

Mednick et al. (1984) published famous research that found a strong link between biological parents and adoptees for property offences but not for violent crimes. 

SCL6A4 and other genes implicated in serotonin pathways have been investigated for their role in impulsivity and drug misuse. Serotonin is a neurotransmitter that has been linked to a variety of processes in the brain, including mood regulation and the firing of the amygdala in the frontal lobe. 

The HTR2B gene, for example, codes for one of the numerous serotonin receptors. Bevilacqua et al. discovered in 2010 that a codon in the HTR2B mRNA that signalled the end of translation (commonly known as the stop codon) was linked to drug misuse and an increased risk of committing impulsive crimes such as homicide and arson. 

However, most of the study on this subject is problematic since the researchers were unable to verify whether the functional variation of HTR2B, that is, a version of the gene that modifies its function, is linked to substance misuse or impulsivity. 

In other words, no conclusions could be drawn as to whether the gene caused a predisposition to substance abuse, which then led to impulsive, criminal behaviour, or whether it caused a predisposition to impulsivity, which then led to a cascade of substance abuse and criminal behaviour — a problem known as “direction of causality.”

MAOA and CDH13.

There’s also the MAOA gene to consider. MAOA, sometimes known as the ‘warrior’ gene, has a tangled history. The MAOA gene produces the monoamine oxidase-A enzyme, which is involved in the breakdown of neurotransmitters like serotonin. 

Individuals with MAOA gene mutations linked to a poor dopamine turnover rate have been proven to be more aggressive than their peers. Scientists frequently utilise ‘knockout experiments,’ which involve altering a gene of interest such that it is knocked out (KO) and no longer functions. 

It allows researchers to see what happens when a gene isn’t working properly, which might lead to more study into the gene’s role and the illnesses it causes, as well as solutions. 

In mice, knockout experiments of MAOA vs MAOB (monoamine oxidase-B) enzymes demonstrate markedly different behaviour depending on whether oxidase-A or oxidase-B is knocked out. (JC Shih, 1999).

Because the two enzymes selectively oxidise distinct substrates, the build-up of specific chemicals when one is knocked out is the most plausible explanation for why MAOA KO mice are aggressive whereas MAOB KO mice are not. 

The recurring generational prevalence of violent criminal behaviour among members of a Dutch family was linked to a rare point mutation in the MAOA gene that resulted in entire inactivation of monoamine oxidase-A. (Brunner HG et al, 1993).

Significant relationships between the low-functioning variation (producing loss or decreased function) of the MAOA genotype and later antisocial outcomes have been found in meta-analytical investigations (Byrd et al, 2014). 

However, the largest research on the subject, which included over 4000 individuals, was struck by the difficulties in defining causal direction once again (Haberstick BC et al, 2014).

It was not possible to determine if MAOA mediated the link between an abusive upbringing and antisocial behaviour. Furthermore, the majority of research in this sector has been undertaken on a male-only population. As a result, research on the MAOA gene has been contentious.

Around the same time, it was discovered that a tiny minority of antisocial, serial criminals was responsible for a high share of violent crime in affluent countries. 

Jari Tiilhonen, now a Professor at the Karolinska Institutet in Sweden, and his colleagues published a groundbreaking Genome-wide association study (GWAS) on the genetic predispositions to violent behaviours and repeat offenders in a cohort of Finnish convicts in 2015. 

They were divided into two groups: violent (those who had been convicted of at least one violent crime such as homicide or manslaughter) and very violent (those who had been convicted of at least ten violent crimes).

A subset of the ‘violent group’ was the ‘very violent group.’ The research included inmates from 19 of Finland’s major prisons, with the exception of those diagnosed with psychosis and those convicted of sexual crimes. 

The low-activity MAOA genotype was discovered to be linked to aggressive behaviour. Interestingly, the findings did not change between boys and girls, and, more critically, childhood maltreatment did not alter the risk, as some earlier research had shown.

For the severely aggressive group, the link was considerably greater. A further strong link was discovered in the severely aggressive group in an SNP (single nucleotide polymorphism) in the CDH13 gene, which codes for neuronal membrane adhesion. 

CDH13 is a gene that genes for the t-cadherin protein, which is involved in neuron proliferation, migration, and connection. Disrupted brain connections and CDH13 have been linked to Attention Deficit Hyperactivity Disorder, or ADHD, and it’s worth remembering that impulsivity is one of the most common symptoms of the disorder.

It’s necessary to ponder a few critical aspects of the Finish Prisoner research at this point. The majority of the crimes perpetrated by the cohort’s perpetrators were non-premeditated, meaning they were not planned ahead of time. 

As a result, the study was almost entirely centred on a definition of violence in which the main quality was ‘impulsivity.’ Distinct sorts of violence (for example, sexual violence, which this study did not include*) may theoretically be regulated by different genetic recipes. 

In Finland, the majority of crimes are committed while under the influence of drugs such as alcohol, which causes a short-term increase in dopamine levels.

Another conclusion from the study revealed that the risk allele (low-activity variation of the MAOA gene) may represent a hereditary risk of developing alcoholism, but only in cases where the individual was exposed to a stressful childhood environment, such as mistreatment, trauma, and so on. 

The study finally revealed that the low-activity MAOA genotype was linked to roughly 9-10% of violent crimes in Finland. This is the moment at which the distinction between scientific responsibility and ethical application to the judicial system blurs dramatically.

Returning to the age-old Nature vs Nurture issue, one way to think about it is that heredity creates a spectrum, and the individual’s environment, both developmental and otherwise, decides where you fall on it. 

A propensity can be latent for a long time, but if it is exposed to a stressful environment and heightened risk factors like malnutrition and trauma, it will appear.

When applying science to society, clinical findings must be balanced against ethical issues. The Italian judge who lowered a sentence based on a genetic susceptibility test that was not firmly rooted in an environmental context may have created a precedent that may ultimately cause more harm than good. 

Their ruling raises a number of issues, including whether a proclivity for violence may be classified as a mental disease. These questions need complex responses, which we may or may not be able to supply.

Overemphasizing the role of genetics in criminal behaviour may result in over-penalization or over-justification (Forzano et al, 2010). Due to genetic predisposition, offenders’ responsibility may be mitigated during trials, resulting in decreased sentences. 

MAOA and CHD13 are referred to as “serial killer genes” by some. If we continue to designate people as “serial killer gene” bearers, we risk a new degree of stigmatisation. 

Labels can lead to widespread discrimination, genetic profiling, muddled social equality standards, and higher punishment without cause. The authors of the seminal Finnish jail research admit this as well. 

‘It is equally important to recognise that, according to the basic principles of forensic psychiatry, only the offender’s actual mental capability (phenotype) matters when punishment or legal responsibility is considered, and putative risk factors per se (such as genotype) have no legal role in the resulting judgement,’ they write.

Conclusion – 

This blog post aimed to answer the question, “Do serial killers have a certain gene?” and reviewed who serial killers are, how their brains work, their traits, functionalities and their genetic composition to help determine if serial killers have a certain gene. Please feel free to reach out to us with any questions or comments you may have.

References –

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What is the “Serial Killer” gene and how does it affect people? Quora. (n.d.). Retrieved from

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