Genetic Determinism and Personal Responsibility

By Caroline Santoro

     Genes make you who you are, but can they make you a criminal? With advances in genome technology, scientists have found genes linked to violent and impulsive behavior. This research raises a series of questions in legal policy ─ should criminals with these genetic variants be given less punishment, or should they be expected to exhibit legal behavior in spite of their genetic predispositions?

     Monoamine Oxidase A (MAOA) is an enzyme responsible for regulating dopamine and serotonin, neurotransmitters that control the brain’s reward system and mood (Levitt, nd). Low activity of MAOA, along with Cadherin 13, a gene involved with impulse control, has been linked to criminal violence (Le Roux, 2014). A study of 900 Finnish criminals who had committed at least ten homicides found that only 5-10% of the criminals had low-activity MAOA. However, this finding has not stopped courts from using low levels of MAOA to reduce sentences on the grounds that defendants’ violence was caused by their genes.

     In 2009, Italian criminal Abdelmalek Bayout’s murder sentence was shortened by a year after the presentation of evidence that he had low-activity MAOA (Korsten, 2009). The Italian court ruled in favor of the variants, but that was not the case for Stephen Mobley, who walked into a pizza store and shot the manager in 1991. While waiting on death row, his lawyers pled that Mobley was genetically predisposed to be a killer, and therefore he was not fully responsible for his crime (Connor, 1995). The court ruled that the genetic research offered insufficient evidence, and he was executed in Georgia in 2005 (Levitt, nd).

     Even if the links between genes and criminal behavior were stronger, should genetic variants be admissible as evidence in criminal trials? According to the Finnish study, the majority of the people with low-activity MAOA have not committed any crimes, and the majority of people who have committed crimes do not have the MAOA variant. In addition, in most cases, the predisposition to violence requires many genes working together. Also, if criminals are less responsible when they possess certain gene variants, are they even less responsible when they have been exposed to a violent environment?

     The widespread acceptance of genetic evidence in courts might encourage criminals to feel that they are not fully responsible for their actions. It would also create a unfair advantage to those who can afford genetic testing and the expert testimony needed to make it an effective defense in court. Even if genes significantly contribute to a person’s likelihood of being violent, so do a multitude of environmental and cultural factors. Arguing that people are not fully responsible for their actions becomes a “slippery slope”─ should anybody be responsible for anything? Ultimately, people have to be responsible for their actions, regardless of the degree of control we believe they have over those actions. Otherwise, why should people resist the urge to be violent if it is written in their genes?

     Supplying an excuse for violence eliminates the reward for self control and licenses criminal behavior. Instead, our understanding of the genetic factors that influence criminal behavior should make us more focused on compassion, prevention, and rehabilitation, rather than focusing on incarceration as revenge. While we should continue to make people accountable for their actions, perhaps one day we can identify genetic inclinations in order to treat people at risk rather than simply wait for them to commit crimes.  


Works Cited


Connor, S. (1995, February 11). Do your genes make you a criminal? Retrieved January 01, 2018, from news/uk/do-your-genes-make-you-a-criminal-15727 14.html


Garcia-Arocena, D. (n.d.). The genetics of violent behavior. Retrieved January 01, 2018, from


Korsten, N. (2009, November 8). Reduced sentence for murderer with ‘genetic predisposition’ to aggression. Retrieved January 01, 2018, from


Le Roux, M. L. (2014, October 28). What makes a criminal? Gene trawl raises questions. Retrieved January 01, 2018, from


Levitt, M. (n.d.). Crime Genes. Retrieved January 01, 2018, from