Impulsive, manipulative and lacking remorse, criminal psychopaths typically face longer and harsher sentences in the justice system. But a growing body of research shows that their aberrant behaviour may be linked to faulty wiring in the brain, challenging the assumption that psychopaths are intrinsically evil and raising questions about how they should be dealt with when they break the law.
Should criminal psychopaths - who make up 15 to 25% of the prison population, according to estimates - be held accountable to the same degree as offenders who don't have the same brain abnormalities? Are they victims of their biology?
The debate is roiling across the fields of criminology, law, philosophy and neuroscience. "I don't think there is a consensus. I think that there is a lot of confusion," said Heidi Maibom, an associate professor of philosophy at Carleton University. A study led by researchers at the University of Wisconsin and published this week in the Journal of Neuroscience is likely to add fuel to the debate.
The researchers scanned the brains of inmates from a local prison, focusing on two key areas: the almond-shaped amygdala, which helps to detect fear and mediate anxiety, and the ventro-medial prefrontal cortex, which is responsible for more complex social emotions, such as guilt, empathy and regret.
One set of data showed that the white fibres connecting these two areas of the brain were weaker in the brains of psychopaths compared to other offenders. Another set of data showed that electro-chemical signals emitted by these two areas were less coordinated in the brains of psychopaths.
"What the science suggests is this is a brain-based disorder and that the neural dysfunction may undermine the ability of these individuals to control their social behaviour and regulate their emotions," said Mike Koenigs, an assistant professor of psychiatry at the school.
While scientists can't say with certainty that these brain abnormalities are the cause of the disorder, they now at least know what area of the brain may be associated with it, he said. Psychopaths should be viewed as patients with neuro-cognitive disorders who may benefit from treatment, Koenigs said.
"We're not talking about turning them into Mother Teresa," Koenigs said. But with cognitive behavioural therapy and drug therapy, it is possible they could become "a little more responsible."Toronto criminal lawyer Graeme Hamilton adds that defence lawyers who use brain scan images in the courtroom to try to get a better outcome for their clients have to consider the possibility that prosecutors could use the same evidence to further their goals.
"If a neurological assessment shows something in the brain that would - based on the current science - suggest potential dangerousness that cannot be treated, then, of course, that could be very detrimental to your client. "It's something that could go both ways."