In this blog post, we explore the relationship between criminal tendencies and genetic factors from the perspectives of brain science and neurocriminology.
On September 13, 1848, blasting operations were underway on a large rock in the Green Mountains of Vermont, USA. Foreman Phineas Gage was tasked with placing explosives in the drilled holes; the procedure involved pouring sand into the charged holes, lighting the fuse, and then retreating to a safe distance. However, on that day, an accident occurred when the powder ignited before the hole had been filled with sand. Phineas was not paying attention at that moment, and with a loud “boom,” an iron rod pierced his head. Remarkably, he survived, and his life was saved thanks to the efforts of Dr. Hallow. This incident attracted significant attention from doctors, not only because Phineas survived but also because his personality underwent a complete 180-degree change following the accident. Phineas, who had previously been cheerful and gentle, began to exhibit erratic and violent tendencies after the accident. The brain injury had caused a change in his personality. This was regarded as a case demonstrating the potential for a connection between biological factors—such as the brain—and psychological factors—such as personality.
The academic discipline that deals with such research is neuroscience. Neuroscience explores the various changes resulting from brain damage, and within this field, neurocriminology specifically studies the link between brain damage and crime. This article will focus on neurocriminology.
The origins of neurocriminology can be traced back to the Italian criminologist Cesare Lombroso. He argued that certain criminals possess distinct physical characteristics and that these traits could be used to identify them. For example, he claimed that thieves and rapists had unique physical features. Furthermore, he asserted that criminality is hereditary, positing that people with a strong genetic predisposition to crime are born with specific physical characteristics. However, his claims were not based on clear statistical data, and as they became linked to eugenics and fascist ideology, they faced criticism and were eventually discarded.
While neurocriminology deals with such sensitive and controversial topics, unlike in Lombroso’s era, current research discusses the possibility that the causes of crime lie in the brain and genes, rather than in an individual’s appearance. In other words, the argument is that the difference between those who commit crimes and those who do not stems from brain structure. According to Professor Adrian Raine, author of *The Anatomy of Violence* and a leading expert in this field, the role of biological factors in explaining criminal behavior has been underestimated compared to environmental factors.
In fact, research has shown that many criminals exhibit palm patterns indicative of less evolved characteristics or possess specific genetic mutations. For example, mutations in the monoamine oxidase A (MAOA) gene are frequently found in the families of criminals. A deficiency in this enzyme can prevent the proper production of neurotransmitters that influence aggression, potentially promoting antisocial behavior. Furthermore, people with damage to the prefrontal cortex often struggle to control their impulses. The area of the brain damaged in Phineas Gage’s accident was also the prefrontal cortex. A study analyzing the brains of 41 murderers found significantly lower activity in the prefrontal cortex. Thus, various biological factors—particularly the link between brain damage and crime—present a possibility worth serious consideration. However, some social scientists place greater emphasis on environmental factors—such as a criminal’s family background or upbringing—rather than biological factors in explaining criminal behavior.
Most people recognize that environmental factors have a significant influence on crime, and it is true that they play a major role in many cases. However, contrary to this perception, there are instances where the environment does not exert a significant influence. For example, there is the case of Jeffrey Landrigan, who was adopted into a peaceful home and received a good education but continued to commit crimes. He met a criminal named Darren Hill in prison who looked exactly like him, and it became a major topic of discussion when it was revealed that Hill was his biological father.
So, between environmental and biological factors, which should we prioritize as the cause of crime? Until now, most societies have believed that environmental factors lead to crime. Indeed, most psychopaths and serial killers we encounter grew up in disadvantaged family environments and often experienced traumatic events during childhood. Furthermore, acknowledging biological factors as the primary cause of crime could be interpreted to mean that criminals are born that way, which raises human rights concerns; consequently, biological factors have often been overlooked.
However, there is a growing body of research suggesting that we need to pay more attention to biological factors. As violent crimes increase in modern society, prevention has become more important than responding after a crime occurs, and identifying the causes of crime has become a key task in this effort. The argument is that since prevention based solely on environmental factors has its limits, biological factors must also be considered. The intent is not to scan everyone’s brains and isolate those with a high likelihood of committing crimes, but rather to keep open the possibility of introducing brain scans for crime prevention. In his book, Professor Adrian Raine argued that by around 2030, it will be possible to predict the likelihood of criminal behavior with over 70% accuracy using a crime prediction algorithm that incorporates both genetic and environmental factors.
We must no longer view this issue solely as a matter of human rights. Sufficient research and evidence have already been accumulated, and logical studies supporting this are currently underway. Of course, just because biological factors increase the likelihood of crime does not mean we can definitively conclude that a person will commit a crime. For example, while some studies suggest that a deficiency in monoamines can trigger antisocial behavior, there are people who exhibit antisocial tendencies without possessing this trait, and there are cases where such tendencies have been overcome through environmental factors. However, it is precisely this point that must be given significant consideration in crime prediction and prevention. This means we must keep the possibility of improvement through environmental factors wide open for individuals who score high on biological factors.
One reason social scientists oppose crime prediction based solely on biological factors is the concern that environmental factors may be neglected. If crime prediction relies exclusively on biological factors, important environmental factors—such as racial discrimination or domestic violence—may be overlooked. However, even with these concerns, a more systematic response would be possible through a balanced crime prediction algorithm that comprehensively considers both biological and environmental factors. Rather than judging solely based on a criminal’s brain structure, we must analyze it comprehensively alongside environmental factors and utilize this in predictions. If a crime prediction algorithm that reflects environmental and biological factors in a balanced manner is introduced into society, it is expected to have a preventive effect.
The brain and crime are distinct yet deeply interconnected concepts. We must elucidate the relationship between these two concepts more systematically and apply this knowledge to actual crime prevention. Although there are limitations such as human rights issues and the impossibility of 100% prediction, if we further strengthen the correlation between crime and the brain as addressed by neurocriminology, there is potential for a safer society. If someone in our immediate circle has a brain profile associated with a high likelihood of criminal behavior, it would be advisable to take preventive environmental measures rather than ignoring it. The key is not to rely entirely on these predictions. This is because, while humans are predictable to some extent, they also possess an equally significant degree of unpredictability. Fundamentally, it is important to create a social environment where crime is difficult to commit, and through this, we can hope to evolve into a better society.
