A man who beheaded a fellow passenger on a Greyhound bus in Canada in 2008 has been granted his freedom.

Will Baker, formerly known as Vince Li, claimed he "heard the voice of God telling him to kill the man or 'die immediately'", when he attacked Tim McClean.

Baker sat next to McLean on the bus after the 22-year-old smiled at him and asked how he was doing.

Shortly afterwards he repeatedly stabbed McLean as other passengers fled the bus. Baker continued stabbing and mutilating the body before he was arrested and severed McLean's head, displaying it to some of the passengers outside the bus, witnesses said.

Baker was diagnosed with schizophrenia and found not criminally responsible for the attack. He was initially kept in a secure wing of a psychiatric hospital but was given more freedom every year.

Baker has been living on his own in a Winnipeg apartment since November, but was still subject to monitoring to ensure he took his medication.

Manitoba's Criminal Code Review Board announced on Friday that he has now been given an absolute discharge, meaning he is longer subject to monitoring.

In a written decision, the review board said it "is of the opinion that the weight of evidence does not substantiate that Mr Baker poses a significant threat to the safety of the public."

Mr McClean's mother, Carol de Delley, who has been outspoken against granting Baker freedom, said in a Facebook post that she had "no words" for the decision.

Baker's doctor, Jeffrey Waldman, told the review board earlier this week that he is confident Baker will remain on his medication and will continue to work with his treatment team if released. Waldman testified that Baker knows it's the medication that keeps his illness at bay.

Waldman said Baker plans to visit his native China if released but would live in Winnipeg for the next two to three years and plans on establishing a career in the city.