Scientific explanation of psychopathy cuts jail time

Serial sex offender Raymond Henry Garland, considered one of Australia's most dangerous sexual predators, was officially diagnosed a psychopath last week. Psychiatrist Joan Lawrence told the Brisbane District Court that Garland had an "almost 100 per cent chance of violent reoffending." Garland has been dealt four indefinite sentences – but research out today suggests that biological evidence of psychopathy could alter the length of such sentences.

Brain scans and genetic tests are becoming a common feature of courtroom battles, as biological evidence is increasingly used to explain a person's criminal behaviour. For example, last year an Italian woman convicted of murdering her sister had her lifetime sentence reduced to 20 years on the basis of brain and genetic tests, which provided biological explanations for her aggressive behaviour.

But does the inclusion of such evidence affect the sentencing of psychopaths – people with a disorder currently thought to be untreatable? Any evidence could act as a double-edged sword, says James Tabery at the University of Utah. A so-called biomechanism to explain psychopathic behaviour could be used to argue that a person is less culpable for their actions, reducing their sentence. On the other hand, the defendant could be seen as more likely to reoffend and receive a longer sentence.

Testing the sword

To find out "which way the sword was going to cut", Tabery, together with psychologist Lisa Aspinwall and law professor Teneille Brown, also at Utah, sent out a survey to 181 US judges based in a number of different states.

Each judge was asked to sentence a convicted criminal diagnosed as a psychopath. The team's fictional character was based on Stephen Mobley, who robbed and then killed a Domino's pizza store manager in 1991. Mobley went on to brag about the crime, and even got the word "Domino" tattooed on his back. Psychologists claimed that his behaviour and lack of remorse was psychopathic and untreatable. At the time, Mobley's request to submit a genetic-based defence for his behaviour was denied, says Tabery. "The Georgia State Supreme Court said [genetic evidence] wouldn't have made any difference," he says. "He was sentenced to death."

In Tabery's fictional case, a man was found guilty of the similar crime of aggravated battery, although the victim was not killed but left with permanent brain damage. The criminal was diagnosed as a psychopath by a psychiatrist. Half of the judges were given additional evidence from a second psychiatrist, who said that the man's behaviour was the result of a genetic mutation that caused a structural abnormality in his brain. Half of each group of judges received the diagnosis as a form of defence, pleading the man's lack of control and culpability over his actions. The other judges saw the diagnosis as part of a prosecution which argued that the man was likely to reoffend.

Shorter sentences

Without a diagnosis, the judges surveyed said they would have given the man a sentence of about nine years. Once he had been diagnosed as an untreatable psychopath, however, the average sentence jumped to 14 years. When judges were presented with biological evidence of the genetic mutation, this sentence was lowered to around 13 years, regardless of whether the evidence was presented by the prosecution or defence.

"We saw both sides of the double-edged sword in play," says Tabery. "The addition of a biological mechanism slightly reduces the sentence compared to just the diagnosis of psychopathy, but it's still significantly higher than what judges said their average sentences are for aggravated battery."

Stephen Morse, professor of law and psychiatry at the University of Pennsylvania in Philadelphia, says that the issue of free will in responsibility for one's actions should be "beside the point" in a court room. "Having free will or not having it is not part of any legal doctrine, and needs never be proven or disproven."

But if biological evidence can swing sentences, should all psychopaths be given the option to include brain scans and genetic tests in their defence? Or should the use of such evidence be ruled out entirely? "Different states and different judges vary in how they process this information," says Tabery.

Morse thinks this variation is a real problem in the criminal justice system. "It's usually up to the judge to decide what factors to balance at sentence, how they should be weighed and what evidence to consider, and that results in very varied sentencing," he says. "I think there should be less discretion involved in sentencing, although judges hate the idea."

Journal reference: Science, DOI: 10.1126/science.1219569