Neuroscientists are shedding new light on these questions by uncovering how brain lesions can lead to criminal behavior. A recent study contains the first systematic review of 17 known cases where criminal behavior was preceded by the onset of a brain lesion. Is there one brain region consistently involved in cases of criminal behavior? No—the researchers found that the lesions were widely distributed throughout different brain regions. However, all the lesions were part of the same functional network, located on different parts of a single circuit that normally allows neurons throughout the brain to cooperate with each other on specific cognitive tasks. In an era of increasing excitement about mapping the brain’s “connectome,” this finding fits with our growing understanding of complex brain functions as residing not in discrete brain regions, but in densely connected networks of neurons spread throughout different parts of the brain.

Interestingly, the ‘criminality-associated network’ identified by the researchers is closely related to networks previously linked with moral decision making. The network is most closely associated with two specific components of moral psychology: theory of mind and value-based decision making. Theory of mind refers to the capacity to understand other people’s points of view, beliefs, and emotions. This helps you appreciate, for instance, how your actions would make another person scared or hurt. Value-based decision making refers to the ability to judge the value of specific actions or their consequences. This helps you see not only what the outcomes of your actions will be, but whether those actions and outcomes are good or bad. The letters written by Charles Whitman on the eve of his killing spree provide a chilling window into a mind losing the ability to understand good, bad, and other people: “It was after much thought that I decided to kill my wife, Kathy…I love her dearly, and she has been as fine a wife to me as any man could ever hope to have. I cannot rationally pinpoint any specific reason for doing this.”