Neuropsychological Markers of Homicide and Violent Offending

According to the Federal Bureau of Investigation, there were an estimated 14,905 homicides in the U.S. during 2018, with a murder rate of 5.0 murders per 100,000 individuals. Numerous costs are associated with homicide, including criminal justice system (e.g., government funds spent on incarceration, prosecution, and adjudication services, etc.) and intangible costs to victims and families (e.g., pain and suffering, decreased quality of life, psychological distress). The average cost per homicide offense in the U.S. is estimated to range from $8.98 million to $17.25 million.

This line of research explores neuropsychological differences between homicide offenders, in order to better inform policy, law enforcement, jurisprudence, and correctional efforts.

Below are examples of completed projects:

Perpetrators of mass murder (defined as 3 or more victims in a single incident) exhibit higher levels of premeditation and better cognitive ability than perpetrators of single-victim homicides. Unlike homicide offenders who killed a single victim, mass murderers demonstrate cognitive abilities that are closer noncriminal controls than violent offenders in general.

Source: Fox, J. M., Brook, M., Stratton, J., & Hanlon, R. E. (2016) Neuropsychological profiles and descriptive classifications of mass murderers. Aggression and Violent Behavior. 30, 94-104. http://dx.doi.org/10.1016/j.avb.2016.06.014

Distinct neuropsychological pathways differentiate perpetrators of intimate partner violence (IPV) from other violent offenders using the Classification And Regression Tree analysis. Findings suggested that individuals with multiple arrests for nonviolent crime, interpersonal traits of psychopathy without attentional difficulties, or a neurodevelopmental diagnosis without interpersonal psychopathic traits may be at enhanced risk for IPV perpetration.

Source: Fox, J. M., Reilly, J., Kosson, D. S.; Brown, A., Hanlon, R. E., & Brook, M. (2020). Differentiating perpetrators of intimate partner violence from other violent offenders using a statistical learning model: The role of cognition and life history variables. Journal of Interpersonal Violence. https://doi.org/10.1177/0886260520918567

Female homicide offenders demonstrate a greater impairment in verbal memory compared to male homicide offenders.

Source: Fox, J. M., Brook, M., Heilbronner, R. L., Susmaras, T., & Hanlon, R. E. (2018). Neuropsychological and criminological features of female homicide offenders. Journal of Forensic Sciences. https://doi.org/10.1111/1556-4029.13911

Greater victim injury severity during the commission of a homicide is associated with certain criminologic and cognitive factors including a greater number of past convictions, using a weapon (particularly a knife), and worse verbal memory performance.

Source: Mazurek, C., Brook, M., Kwasny, M., & Hanlon, R. E. (2020). Homicidal Physical Violence: An Exploratory Analysis of Relevant Cognitive, Demographic, and Criminological Factors in a Sample of Murderers. Homicide Studies. https://doi.org/10.1177/1088767920935161

Offenders who commit impulsive (as opposed to premeditated) homicide demonstrate greater cognitive impairment, particularly in the domains of verbal intelligence, verbal memory, and attentional / executive functioning. In contrast, premeditated murderers demonstrate largely intact functioning across cognitive domains.

Source: Hanlon, R. E., Brook, M., Stratton, J., Jensen, M., & Rubin, L. H. (2013). Neuropsychological and intellectual differences between types of murderers: affective/impulsive vs. predatory/instrumental (premeditated) homicide. Criminal Justice and Behavior. 40(8), 933-948. https://doi.org/10.1177/0093854813479779

Offenders who specifically had killed children are more likely to present with histories of head trauma, psychopathology including substance abuse, and neurocognitive impairment, compared to those offenders who also had adult victims. Among murderers of children, spontaneous domestic homicide emerged as a distinct criminologic subtype, distinguished by greater neuropsychological impairment and a more affectively driven presentation.

Source: Azores-Gococo, N. M., Brook, M., Teralandur, S. P., & Hanlon, R. E. (2017). Killing a child: Neuropsychological profiles of murderers of children. Criminal Justice and Behavior. 44(7), 946-962. doi: https://doi.org/10.1177/0093854817699437