MONTREAL - A Montreal firefighter was convicted of manslaughter Thursday after his sex partner died in a choking game during a sadomasochistic tryst in his basement.

Patrick Deschatelets, 45, was also found guilty of criminal negligence in the 2008 death of a woman whose identity is covered by a publication ban.

She died during a marathon sexual encounter in February 2008 after she was asphyxiated by a metal collar that Deschatelets had put around her neck.

The collar was suspended from the ceiling by a chain in Deschatelets's home in St-Bruno-de-Montarville, QC, south of Montreal.

He left the woman alone and went to buy pasta at the grocery store. When he returned, she was unconscious, hanging from the chain. She died a few hours later in hospital.

During the police interrogation, Deschatelets said his partner "consented 100%" to the choking game. The S and M maneuver was part of a 48-hour-long submission ritual that the defendant's lawyer said was a "usual" practice for the pair, who had been dating for a few months.

A letter, written by the victim and recounting her final hours, was found on Deschatelets's computer.

During closing arguments, defence lawyer Jean-Paul Perron told court that Deschatelets was not responsible for the woman's death.

The lawyer suggested the woman had choked herself in an attempt at sexual stimulation.

Crown prosecutor Marie-Claude Morin said that while sex games are not illegal, Deschatelets should not have left the woman alone. Morin added that the victim was hanging by the head, which is a vulnerable area of the body.