Scientists can measure criminal intent — at least in the moment

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(Illustration by Michael S. Helfenbein)

Intent to commit a crime is a crucial factor in determining prison sentences, yet some theorists have worried that different grades of criminal intent are fictions and so should not be given weight in courtrooms.

A new neuroimaging study suggests it is possible to measure the subtle variations in intent that matter to law — at least while a crime is being committed. Brain activity reveals whether people know they are committing a crime or are merely being reckless, according to research published the week of March 6 in the Proceedings of the National Academy of Sciences.

“We are not replacing juries with brain scanners, but we can now say that some debated differences in degree of criminal intent have a real neural basis,” said Yale’s Gideon Yaffe, professor of law, philosophy, and psychology.

Researchers from Yale University and the Virginia Tech Carilion Institute, under the auspices of the MacArthur Foundation’s Research Network on Law and Neuroscience, asked 40 subjects to decide whether to take a suitcase  through a security checkpoint. During some trials, the subjects knew there was contraband in the suitcase. In others, they were aware only that there was a risk they might be carrying contraband. The subjects knew they would be rewarded for sneaking contraband through, but punished if caught carrying it.

By examining neuro-images of the brains of these subjects as they made their choices, researchers were able to predict which subjects knew they were carrying contraband and which were aware only of a risk.

In the law, these distinctions are important both for establishing guilt and for sentencing. In general, knowing actors are guilty of more serious offenses and punished more harshly than reckless actors.

Yaffe says it might not be possible, even in principle, to use neuroimaging to answer the question of criminal intent after the fact. However, these results do suggest that future neuroimaging studies could help to assess the mindsets, during crimes, of people with mental illnesses or addictions.

“For instance, does an addict who leaves his child in a hot car while he seeks drugs really understand the risks involved? Maybe not. Or maybe he is even more vividly aware of them than non-addicts,” Yaffe said. “Neuroscience might help us to answer those questions.”

Science & Technology

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Bill Hathaway: william.hathaway@yale.edu, 203-432-1322