Vince Li, a Chinese immigrant who became a Canadian citizen in 2007, was declared not criminally responsible for the killing of Tim McLean on a Greyhound bus in 2008. (John Woods/Canadian Press)

Doctors treating the man who stabbed and beheaded a passenger aboard a Greyhound bus are asking that he be allowed short periods of supervised outdoor time on the grounds of the Manitoba mental-health facility where he's being held.

Vince Li, 41, returned to a Winnipeg courtroom on Monday for a mandatory annual review of his detention at a mental-health facility in Selkirk, north of Winnipeg.

The Criminal Code Review Board conducts the annual review of his detention and care.

At the hearing, Li's doctors asked the board to consider allowing Li 15-minute escorted walks on the grounds of the Selkirk Mental Health Centre. He's currently being held in a secure part of the facility. The Crown and victim Tim McLean's family are opposed to the move.

In early 2009, Li was found not criminally responsible for killing McLean, 22, aboard a Greyhound bus bound for Winnipeg in July 2008.

Li had pleaded not guilty to a charge of second-degree murder. Psychiatric evidence at his trial suggested he is schizophrenic and suffered a major psychotic episode when he fatally stabbed McLean, ate some of the body parts, and cut off McLean's head.

'I think he should be held for the rest of his life.'—Carol DeDelley

Rather than being held in prison, Li is being kept in the secure psychiatric facility. The review board is responsible for assessing whether Li should remain institutionalized or be given a conditional release, which is unlikely.

Dressed in a dark suit and sneakers, Li was seated in the courtroom in such a way that he did not face the gallery, where a number of members of McLean's family were sitting.

McLean's mother, Carol DeDelley, said after the hearing that her son's killer should never be allowed out of the secure part of the facility.

"I think he should be held for the rest of his life," DeDelley said.

"I struggle to get through a day without crying over the details of my son's death," DeDelley wrote in a victim impact statement. "I don't want to see the visions in my mind, but they are still there. I don't want to be here speaking to the review board. I feel I have to be."

Bruce Martin, the man who drove the bus on the night of the attack, and who only recently returned to regular duties, told the board his only relief is knowing Li is "under lock and key."

"I have some comfort knowing that our citizens, and their children and grandchildren do not have to fear [Li]," Martin wrote in a statement read by his wife.

Li sat slumped over as his doctor answered questions about his treatment.

The review board members heard that Li continues to be medicated with anti-psychotic drugs. He is also now being treated with antidepressants.

Li's risk of suicide has been downgraded to low, the members heard, and Dr. Steven Kremer, Li's psychiatrist, suggested this might have something to do with him taking the antidepressant medication.

Behaviour unpredictable: doctor

Questions were asked about the risk Li poses to the general public.

The board heard that Li has been participating in programming and has not refused treatment that's been offered to him.

Kremer did not suggest that these positive factors support Li's release from custody.

"We can not predict an individual's future behaviour with 100 per cent certainty," he said.

Li still keeps largely to himself, but has had regular contact with his wife, Ana, over the past year, the board heard.

It's not the first time Li has spent time in a mental-health facility.

In 2005, he went to Ontario from Winnipeg in search of employment, according to review board documents.

The documents said he was picked up by police walking on the highway on his way back to Winnipeg and was admitted to William Osler Health Centre in Etobicoke.

It is not known when the review board will issue its decision on whether Li will stay in custody, but members indicated it could be within a few days.

With files from the CBC's James Turner, Sean Kavanagh and The Canadian Press