A lawyer in Canada, whose client was convicted of murder after stabbing a friend who sexually assaulted him, has appealed that sexuality was wrongly made a major factor in the case.

On Friday Brent Olthuis told an appeal panel of three judges that the conviction of his client, Cory Bird, wrongly ignored the sexual assault that he claims prompted the murder.

The judge who convicted Bird claimed that since he was bisexual he would not have killed his male assaulter out of passion, since he would find sexual contact with men “normal”.

Bird was convicted of second-degree murder after he admitted to stabbing Albert Mitchell 73 times.

He had met Mitchell while hitchhiking, and stayed at Mitchell’s house in British Columbia for a week in 2008. On the last night of his stay Bird said he woke up to find Mitchell, who he had no previous sexual relationship with, sexually assaulting him.

He said he then became “frenzied” and went to the kitchen, where he found a knife and repeatedly stabbed Mitchell.

At his conviction Justice Richard Blair dismissed the claim that Bird was enraged by Mitchell’s sexual advances.

The judge claimed that Bird, a bisexual man, would not have lost control in that situation, as he had previously had sexual contact with men.

The conviction stated: “[Bird] says that he is bisexual and, as such, appears to accept sexual contact with other males as a normal manifestation of his sexual makeup.”

Mr Olthuis now says the judge unfairly dismissed the sexual assault element of the case by ignoring that, unlike Bird’s previous relations with men, it was non-consensual.

He told the appeal panel: “The justice erred in thinking consensual same-sex relationships in the past had any effect on this uninvited advance.”

Bird changed his story several times after his arrest, claiming Mitchell had threatened him with a knife when he woke up, and that he had killed him as part of a gang initiation.

He was sentenced to life in prison in 2011.