In the US Model Penal Code, a suspect's state of mind while committing a crime can drastically affect the punishment they receive. Specifically, someone who knew that what they were doing was wrong will face harsher penalties than someone who was acting recklessly or negligently. The problem is that it can be hard to know for sure where that line is. In a move that could help clear things up, neuroscientists from Virginia Tech have found that brain imaging techniques can tell the difference, which may help inform future law.

First developed in the early 1960s, the Model Penal Code divides a person's culpability for a criminal act into four mental states: purposely, knowingly, recklessly and negligently. If someone sets out to commit a crime, they're said to do so "purposely," which carries the strictest punishment. "Knowingly" means the person understood they were breaking the law but performed the act anyway, although it wasn't their explicit intention. A reasonable person who disregards a substantial and unjustifiable risk is said to be acting "recklessly," while someone who was merely acting "negligently" wasn't aware of a risk or law, even if they should have been.

The line between knowledge and recklessness is arguably the most important. Since it hinges on whether a person intended to commit a crime or not, it's the largest gap in the severity of the punishment, and can mean the difference between murder and manslaughter.

"People can commit exactly the same crime in all of its elements and circumstances, and depending on their mental states, the difference could be one would go to jail for 14 years and the other would get probation," says Read Montague, lead researcher on the study. "Predicated on which side of the boundary you are on between acting knowingly and recklessly, you can differentially be deprived of your freedom."

To study whether a visible difference between these two states can be detected in the brain, the Virginia Tech team tested 40 people with a hypothetical scenario of drug smuggling. While inside an fMRI machine, participants were asked to pick a suitcase from a group of between one and five cases, one of which contained "contraband," and decide whether they would carry it across the border, knowing a certain likelihood that the case would be searched.

If given only one suitcase, the participant would know for certain that it contained contraband, but the more cases they had to choose from, the less likely it was that theirs had drugs inside. That gives the researchers a sliding scale to spot the difference between someone who is knowingly breaking the law and someone who is recklessly disregarding a known risk.

Using machine learning algorithms to analyze the resulting brain scans, the results indicated that the brain lights up differently in people who are knowingly committing a crime, versus those who are merely accepting the risk. While it's an interesting finding, and could potentially inform how guilt is determined, the researchers are careful to point out that it's still early days for the so-called science of "neurolaw" and the technology is far from ready to be put to work in determining a real person's future freedom.

"In principle, we are showing these brain states can be detected when the activity is taking place," says Montague. "Given that, we can start asking questions like, which neural circuits are engaged by this? What does the distribution look like across 4,000 people instead of 40 people? Are there conditions of either development, states of mind, use of pharmacological substances, or incurred injuries that impinge on these networks in ways that would inform the punishment?"

The research was published in the journal Proceedings of the National Academy of Sciences, and Montague discusses the work in the video below. (Video courtesy of Virginia Tech)

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