TORONTO -- Alek Minassian's autism spectrum disorder left him incapable of making a rational choice when he chose to drive a van down a Toronto sidewalk and kill 10 people, his defence lawyer argued Thursday.

Boris Bytensky said in closing arguments at Minassian's trial that the 28-year-old's disorder left him without the ability to develop empathy and, ultimately, he was unable to know what he did was morally wrong.

"To be able to make a rational choice you have to have a general awareness of the key facts that go into that rational decision and the key facts have to include ... some sense of the degree of impact you're having on other people," Bytensky said.

Minassian had no idea how horrific his actions were to his victims, his family and the community, the lawyer said.

Minassian has pleaded not guilty to 10 counts of first-degree murder and 16 of attempted murder.The defence argues he is not criminally responsible for his actions on April 23, 2018, due to autism spectrum disorder.

Minassian's state of mind at the time is the only issue at trial after he admitted to planning and carrying out the attack.

Bytensky pointed to Minassian's own words as proof of his lack of rational thinking.

The lawyer noted that in an interview with a forensic psychiatrist who testified for the defence, Minassian indicated that both committing mass murder and building an app were accomplishments.

"You've done something, you've been proactive and you accomplished something," Minassian said in that interview.

That, Bytensky said, is a window into Minassian's mind.

"He's talking about them as equivalents," Bytensky said.

The defence is trying to prove on a balance of probabilities that it's more likely than not that Minassian had a mental disorder that impacted his actions to the extent that he didn't understand what he was doing was wrong.

Autism spectrum disorder played a key role in Minassian's decision to commit the attack and distorted his way of thinking similar to psychosis, his lawyer told the court.

Minassian had a "hyper focus" on mass murders and a website that arranged killers by a score, like a leaderboard of death, court has heard.

He said he wanted to kill 100 people in his original plan that involved a different location, and he wanted to "set a world record" with a high "kill count," Bytensky said.

When Minassian was asked if he'd carry out the attack, again he replied that he might in order to "get another kill count," the lawyer said.

That focus on a high number of victims is a reflection of his state of mind, Bytensky said.

"His hyper focus does not allow for rational choice," he said.

The lawyer said Minassian was not angry at women, as he initially told police.

That was a ruse to boost his notoriety, Bytensky said, by tying his name to the so-called "incel" movement, men who are involuntarily celibate, some of whom have committed mass murders.

Court has heard that Minassian told numerous assessors that he knew what he did was wrong.

But his lawyer said he doesn't understand what he did was morally wrong.

"He does not have the ability to take full stock of all the of the key factors in order to rationally chose whether or not to do the act," Bytensky said to the judge