Justice Michael Code ordered the assessment Monday after Chiheb Esseghaier told the court he had been created by God to "warn mankind" about "hellfire" if the messages of the Qur'an weren't followed.
Esseghaier and his co-accused , Raed Jaser, were found guilty in March of a terror-related conspiracy to commit murder, which carries a sentence of up to life in prison. The jury also found the men guilty of six other terror-related charges between them.
Jaser is already undergoing a mental health assessment, but his lawyers will decide how much of that report to present to the court when arguments for his sentence are made.
Esseghaier is self-represented, but a court-appointed lawyer who is assisting him through the legal process argued that a similar assessment ought to be ordered for the Tunisian national because his mental health was "a real issue."
"This is all about fairness," said Russell Silverstein. "A psychiatrist appointed by the court would... be able to tell you whether these are all the behavioural manifestations of a religious zealot or whether there is an aspect to Mr. Esseghaier that falls under the Mental Health Act."
The request was opposed by Crown prosecutors, who argued that the 32-year-old Esseghaier's extreme religious beliefs didn't warrant a mental health assessment, which would prolong the sentencing phase of the case.
"Court should be really loathe to order an intrusive psychiatric assessment," Crown prosecutor Croft Michaelson said. "Your decision should primarily be based on what you yourself have observed."
Esseghaier — who refused to participate in his trial because he wanted to be judged under the rules of the Qur'an — said he wouldn't mind talking to doctors because he's always eager to share his religious values.
"This doesn't mean that I approve that I have mental problems," he said in court. "It's my duty to invite people to God...that's why I accept to meet with whoever person."
Esseghaier added that religious prophets had been called "crazy" in the past.
"God, out of mercy for humankind, he renew his warning through my case out," he said emphatically. "That's why he created me."
After hearing all sides, Code ruled that while Esseghaier's conduct in court had always been "understandable and consistent," a psychiatric assessment might help the case.
"I do not think that strong religious beliefs, even extreme ones, can be equated with 'mental disorder,'" he said. "On the other hand, what I do not know is whether there is something about Mr. Esseghaier's personality structure that makes him susceptible to religious extremism...this is a point on which I require expert assistance."
Code noted that the assessment — which would be presented to him in full — was unlikely to make Esseghaier appear worse than he already seemed.
"The existing record before me, both on the trail record and from the pre-sentence report that has already been produced, is generally unfavourable to him," Code said, noting that conviction appeared to have had "no impact" on Esseghaier, who was still considered a risk to the community.
Sentencing arguments for Jaser and Esseghaier aren't expected to fully get underway until July.
Their trial, which began Feb. 2, heard that an undercover FBI agent gained the men's trust and secretly recorded hours of their conversations.
The pair were heard musing about alleged terror plots which could be carried out in retaliation for Canadian military action in Muslim lands, and court heard specifically about the alleged train derailment plot targeting a train between Canada and the U.S.