Terrence Kain killed his mother in their home. Photo: Supplied

After an argument with his elderly mother about his smoking, Terrence Kain strangled her to death. Then, he phoned his sister. "Mum's dead," he told her. "I strangled her. She's dead."

Kain, of Goulburn in NSW, openly admitted to killing his mother. While the confession may make it seem like an open-and-shut case with a clear murder verdict, that was not what the court decided.

In sentencing the 48-year-old earlier this year, Justice Michael Adams said while Kain realised he was seriously hurting his mother, he had not intended to kill or harm her.


Murky area: If actions are determined by how well the brain is working, what does that say about free will? Photo: Jessica Shapiro

Kain had a history of heavy drinking. He had also had one of his legs amputated after shooting himself and, most importantly for his defence, he suffered from chronic brain damage and dementia.

In other words, if it had not been for his brain damage, Kain would never have harmed his mother. The court accepted he was not in control of his actions and he was charged with manslaughter, rather than murder, eligible for release in 2015.

As more is uncovered about the complexities of the brain and its role in behaviour, neuroscience is increasingly coming into play in court cases such as Kain's. Neuroscience and behavioural genetics, which aims to uncover the role of genetics in determining behaviour, are making criminal sentencing harder.

Medical sketch of man's head with brain placement.

Neurolaw is attracting increasing interest. Photo: Antar Dayal

The interaction between those fields with civil and criminal law is known as neurolaw, and it is attracting increasing interest from lawyers, neuroscientists, behavioural geneticists, forensic psychiatrists, forensic psychologists and philosophers.

Allan McCay, a former associate solicitor with global law firm Baker and McKenzie, is involved in constructing the first Australian neurolaw database at Macquarie University's Centre for Agency Value and Ethics in New South Wales. It aims to establish how neurolaw is playing out in Australia and provide a resource for legal practitioners, legal academics and philosophers involved in complex cases.

"Is what we do just a matter of luck in how we are constituted, and down to events relating to neurotransmitters and enzymes in our brain?" McCay asks. "If this picture of us is correct, are we really responsible for what we do? Some of the questions raised by neuroscience bring us close to the free will debate that has perplexed philosophers throughout the ages.

"The interest in these issues goes beyond purely legal interest and into philosophy, as some of the issues that are raised in neuroscience cases call into question our place in the world."

Using scientific evidence, however, is not always easy. While studies in behavioural genetics show certain gene and environment combinations correlate with antisocial conduct, many of the studies have not been replicated, which raises questions about their reliability.

"But even if the science is credible, then one might ask: what can be inferred from it about a person's moral and legal responsibility for what they have done?" McCay says. "Another question is that of the degree to which the law does and should care about the degree of responsibility of blameworthiness.

"Perhaps the law should focus more on protecting others from the dangerous. Science cannot answer the further questions like this. The answers have to come from ethics and law."

In 2000, renowned American neuroscientist and director of the University of Kansas Alzheimer's Disease Centre, Russell Swerdlow, published a patient case study that has become famous in the field of neurolaw.

In the journal Archives of Neurology, Swerdlow wrote that a 40-year-old married schoolteacher began to have a sexual interest in children seemingly out of the blue. The teacher downloaded and viewed child pornography. When his stepdaughter complained that he was making sexual advances towards her, the man was arrested.

A court ordered him to go through a rehabilitation program if he wanted to avoid jail, but he continued to make advances towards the staff there and was expelled. Because he had failed the program, he would need to face the court and jail time again.

However, the night before sentencing, he went to a hospital emergency department complaining of headaches. He urinated on himself, sexually harassed staff, could no longer write legibly and spoke about wanting to rape his landlady.

A magnetic resonance imaging (MRI) scan revealed the teacher had a large, egg-sized orbitofrontal tumour on an area of his brain associated with social behaviour. Surgeons removed the tumour and his criminal behaviour ceased. He successfully completed the sexual rehabilitation program and it was determined that he was no longer a threat to society.

Yet one year later, he was discovered collecting child pornography again. He also complained that his headaches had returned. A scan revealed the tumour had regrown. It is thought that while everyone has hidden desires and urges, they are able to keep a lid on them through the area of the brain that controls decision-making and behaviour. With this area impaired, that lid was completely lifted in the man, taking away his ability to control his hidden and inappropriate urges.

Swerdlow was among those treating the man and said while abnormal behaviour was quite commonly seen in patients with brain tumours, it was the first case he knew of that had led to paedophilia. He provided a testimony at the man's sentencing.

"I never maintained he should be blamed or not blamed for his actions," Swerdlow says. "I was in a position that allowed me to be impartial and non-judgmental.

"I simply pointed out his behaviour probably would not be expected to have happened in the absence of the tumour, and also pointed out that surgery, rather than incarceration, was more likely to bring about the desired outcome – to no longer pose a threat to others."

However, a complicating factor in the case was that although the patient seemed unable to control his urges, he was aware his behaviour was wrong. So if actions are determined by how well the brain is working, what does that say about free will? It's a murky area that needs to be considered in each case like this.

This complexity occurred in a similar case in the United States, where a previously law-abiding man began to download child pornography after surgery to remove a piece of his brain to treat severe epilepsy. Eventually, he was diagnosed with Kluver-Bucy syndrome, caused by damage to the anterior temporal lobes in the brain and leading to irresistible urges for food and sex.

Although he downloaded the illegal material at home, he never did so while at work. The prosecution argued this showed he was in control of his behaviour at least some of the times, and he had an obligation and the capacity to take responsibility and seek help. But instead he wasn't found out until federal police discovered his downloads and turned up to arrest him.

While he was sentenced to a federal prison for two years, the prosecution had pushed to lock him away for five. In the end, the judge agreed the man had shown some evidence of being in control of his actions, at least while at work.

Since writing about this case, Swerdlow says he has occasionally been asked to review other court cases by defence lawyers, but often, using neurolaw is inappropriate and people may try to abuse the field.

"Most of the time I have told the defence lawyers I suspect at face value I would not be able to help them – the claims were kind of silly. It is my impression, though, that this type of legal defence is being tried more and more often."