The only option for the man who carried out the Toronto van attack is to claim a serious mental disorder led to the deadly rampage when he goes on trial next year, according to two lawyers with expertise in mental health.

But Alek Minassian has little hope of being found not criminally responsible (NCR), says Ian Scott, a lawyer and professor at Western University, in part because of his behaviour during a police interview shortly after the attack, a recording of which was released last week.

"His defences are extremely limited," said Scott, who says an NCR argument is Minassian's only conceivable option.

"If he doesn't try that… I frankly don't know what he's going to do other than plead guilty," said Scott, who also sits on the Ontario Review Board, which reviews the status of people found not criminally responsible.

A person can be found NCR if they are deemed to have been suffering from a serious mental disorder at the time of an offence. That determination is typically made following a detailed assessment by forensic psychiatrists, a medical specialty with a focus on law and crime.

Recent examples include Rohinie Bisesar, who was found NCR for the 2015 killing of a stranger in Toronto's underground PATH system, and Matthew de Grood, who killed five people at a Calgary house party in 2014.

The 10 people killed in the attack were, from top left: Sohe Chung, 22, Renuka Amarasingha, 45, Andrea Bradden, 33, Dorothy Sewell, 80, Geraldine Brady, 83; from bottom left, Munir Najjar, 85, Anne Marie D'Amico, 30, Ji Hun Kim, 22, Betty Forsyth, 94, and Chul Min (Eddie) Kang, 45. (Ben Shannon/CBC)

Minassian is charged with killing 10 people and injuring 16 others after he drove a rented van down a busy sidewalk on Toronto's Yonge Street on April 23, 2018.

He admitted to the attack during the police interview. Minassian said it was motivated by incel ("involuntary celibate") ideology, a violent and misogynistic internet subculture dominated by men frustrated by their lack of success with women.

When asked by a police detective how he felt about the attack, Minassian said: "I feel like I accomplished my mission."

His trial is scheduled for February 2020, and is expected to focus on his mental state. It will be heard by a judge alone.

Dr. Gary Chaimowitz, the head of forensic psychiatry at St. Joseph's Healthcare in Hamilton, said an NCR recommendation can be made in one of two ways: if a person did not know what they did was wrong from a legal or moral perspective, or if the person did not understand the "nature and quality" of their actions.

"Were the actions a result of that mental disorder? That is going to be the key question," with Minassian, he told CBC Toronto.

If an NCR argument is made at the trial, Chaimowitz said Minassian would likely be assessed by multiple forensic psychiatry teams, who would spend upwards of 60 days vigorously examining his mental state.

Scott, who has read transcripts and seen portions of the four-hour interview, said Minassian does not appear to display any signs associated with serious mental disorders.

He said those offenders typically struggle with disorganized speech and behaviour, and are most often diagnosed with a form of schizophrenia.

"When I look at the excerpt from the video, we just don't see any of that," Scott said.

Instead, Minassian appears responsive, coherent and fully aware that his actions caused the deaths of multiple victims, Scott continued.

Forensic psychiatrist Gary Chaimowitz said Minassian will likely face rigorous mental health assessments from multiple teams of medical experts. (McMaster University)

Stephen Hebscher, a criminal defence lawyer who also sits on the Ontario Review Board, added that a person found not criminally responsible must also display a sharp break from the real world.

"The behaviour would be driven by a belief that's not based in reality, it's based in a psychotic illness," he said.

In the 1970s, Hebscher said it was more common for offenders to be found not criminally responsible due to psychopathic and sociopathic tendencies. He says the bar is now higher, and that people must be in a legitimate "psychotic state" at the time of their actions.

While some people found NCR can be granted parole and even full discharges, the most serious offenders can spend decades inside maximum security mental health facilities.

"Some people might think being found NCR is like a get-out-of-jail free card, but it simply isn't," said Scott, pointing to a recent case of an offender who has spent 42 years in the system.

"You don't walk out of a hospital or a jail into the community," added Chaimowitz.

The Ontario Review Board oversees approximately 1,500 people who have been found NCR, and reviews each of their cases annually.