Brain injuries linked to criminal behavior highlight importance of white matter tract damage

A new study published in Molecular Psychiatry sheds light on a question that is increasingly debated in courtrooms: Can brain injuries cause someone to commit a crime? Researchers found that damage to a specific white matter tract in the brain—the right uncinate fasciculus—was more commonly seen in people who developed criminal behavior after a brain lesion, especially those who engaged in violent acts. The results support a link between injury to this tract and the emergence of antisocial or aggressive behavior.

The researchers were motivated by a growing trend in which brain imaging is used as evidence in criminal trials. In high-profile cases, such as the 2018 Tree of Life synagogue shooting and the 2023 Lewiston, Maine shooting, defense teams and medical experts pointed to brain damage as a possible factor contributing to violent actions. While these claims are often controversial and difficult to interpret, they reflect a broader need to understand whether brain lesions—especially those affecting white matter pathways—can play a meaningful role in criminal behavior.

Previous research has shown that people with antisocial traits or criminal histories sometimes have abnormalities in certain brain areas, including white matter tracts like the uncinate fasciculus. But these findings have mostly been correlational, making it unclear whether the brain differences caused the behavior, were a result of it, or were entirely unrelated.

To address this, the authors of the new study focused on a rare group of individuals who had no criminal history but developed criminal behavior following a focal brain injury. By studying this kind of “acquired criminality,” they aimed to explore whether injury to specific brain pathways could play a causal role.

“As a Behavioral Neurologist, I often evaluate patients who have changes in social behavior with the onset of a degenerative disease or after a stroke,” said study author Isaiah Kletenik, an assistant professor of neurology at Harvard Medical School, associate neurologist at Brigham and Women’s Hospital, and researcher at the Center for Brain Circuit Therapeutics.

“In rare cases, patients who had previously been law-abiding may even start committing crimes. These clinical cases raised important questions about the brain basis of moral decision-making and led me to pursue network-based neuroimaging analysis of cases of lesion-associated criminality at the Center for Brain Circuit Therapeutics at Brigham and Women’s Hospital and Harvard Medical School.”

The researchers began by identifying 17 individuals from the medical literature who had experienced a focal brain lesion followed by the onset of criminal behavior. These cases were carefully selected to ensure that the behavior started after the injury, and in some instances, the behavior stopped when the lesion was treated—such as when a brain tumor was removed. They compared these cases to a large control group of 706 individuals who also had focal brain lesions but developed other neuropsychiatric symptoms, not criminality. All lesion locations were mapped onto standardized brain templates.

The study used three different approaches to examine whether specific white matter tracts were affected in people who became criminal after their injury. First, the researchers tested whether the lesions overlapped with the right uncinate fasciculus, a tract known to connect areas involved in emotion and social behavior. Second, they expanded the analysis to include 68 white matter tracts from a well-established brain atlas, looking for any that were disproportionately damaged in the criminality group. Third, they conducted a connectome-wide analysis to map structural connections between each lesion and the rest of the brain, identifying which connections were most disrupted in the criminal group.

All three methods pointed to the same primary result: the right uncinate fasciculus was the white matter tract most strongly associated with lesion-induced criminality. In fact, 71% of the lesions in the criminality group intersected this tract, compared to only 14% in the control group. When the researchers focused only on individuals who had committed violent crimes, the association with the right uncinate fasciculus remained strong and was even more distinct.

“The right lateralization of our findings is quite interesting and adds to a growing literature on the role of the right hemisphere in social cognition,” Kletenik told PsyPost.

In addition to the right uncinate, other white matter tracts were also implicated, including the forceps minor, parts of the cingulum, and corticostriatal tracts. These pathways connect various regions of the frontal lobe with limbic and subcortical structures that are important for decision-making, impulse control, and emotional regulation. Still, the right uncinate fasciculus stood out as the most consistently associated with criminal behavior across all analytical approaches.

The uncinate fasciculus links the amygdala and anterior temporal lobe with the orbitofrontal cortex. These brain regions are involved in processing emotions, evaluating rewards and consequences, and making social decisions. When this pathway is damaged, people may struggle to regulate emotions, interpret social cues, or control impulses. Prior research has shown that alterations in the uncinate fasciculus are common in people with psychopathy and conduct disorder. The new findings strengthen the argument that damage to this specific connection can lead to behaviors that violate social norms or laws.

The results have implications for how courts might evaluate claims that brain damage contributed to a crime. If a person with no history of criminal behavior suddenly commits a violent act after suffering a stroke or tumor that affects the right uncinate fasciculus, the location of the lesion could be one piece of evidence suggesting that the injury played a role. Still, the decision to accept such evidence must weigh many other factors, including the type of behavior, the nature of the lesion, and the person’s overall mental and neurological status.

“Brain imaging data is increasingly being introduced into the courtroom to determine factors that could be mitigating or exculpatory to a defendant but there is limited scientific research to guide interpretation of this neuroimaging data, resulting in a reliance on expert opinions that can often conflict with one another,” Kletenik explained. “While rare, some cases of brain injury can cause new onset criminal behavior and can help answer questions about which locations of injury are more likely to impact behavior.”

“We found that injury to the region of a specific brain pathway called the uncinate fasciculus on the right side of the brain was most consistently associated with lesion-induced criminality. This pathway connects regions of the brain involved in decision-making and emotion processing. Our results suggest that if an individual has a new brain injury to specific brain pathways, especially to the right uncinate fasciculus, and has new onset criminal behavior, there is an increased likelihood that the injury plays a causal role in the behavior.”

Despite its insights, the study has some limitations. The number of lesion-induced criminality cases available in the medical literature is small, which limits statistical power and generalizability. The included cases varied in the type and cause of injury, the time between injury and behavior, and the specific crimes committed. Some cases lacked detailed behavioral or personality assessments. There may also be publication bias, as cases linking brain injury to criminality might be more likely to be reported.

Importantly, the researchers emphasized that damage to the right uncinate fasciculus is neither necessary nor sufficient to cause criminal behavior. Not all individuals who developed criminality had lesions intersecting this tract, and some control cases—people with other neuropsychiatric symptoms—also had damage to the uncinate without becoming criminal.

In fact, other disorders such as mania, confabulation, or Capgras delusion were also linked to this tract, though not as strongly. This suggests that while the right uncinate may play a key role in the risk for criminal behavior, other factors likely influence whether that risk turns into action.

“While most subjects with lesion-induced criminality showed some degree of intersection with the uncincate, this is not specific to criminality,” Kletenik explained. “The fact is, other lesion induced syndromes also intersect the uncinate, and it is highly likely that many people have abnormalities in similar locations but do not commit crimes. Even if an individual has a recent injury to the right uncinate, it does not follow that they will commit crimes. Specific locations of brain injury likely predispose someone to certain behaviors, but there are many additional genetic, developmental, social, cultural and environmental factors that are likely important in determining whether the behavior is expressed.”

“Furthermore, causality in science is not defined in the same way as culpability in the eyes of the law. Still, our findings provide useful data that can help inform this discussion and contributes to our growing knowledge about how social behavior is mediated by the brain.”

“We collaborated with philosopher Dr. Patricia Churchland who is a pioneer in the field of neurophilosophy to consider the ethical implications of our findings,” Kletenik added.

The study, “White matter disconnection in acquired criminality,” was authored by Isaiah Kletenik, Christopher M. Filley, Alexander L. Cohen, William Drew, Patricia S. Churchland, R. Ryan Darby, and Michael D. Fox.