There was a rare turn of events at the Montreal courthouse Tuesday when a judge offered immunity to a convicted murderer in exchange for the whereabouts of the victim's body.

Marchat Marseille, 20, was convicted of shooting David Mutunzi Nyagahene, 17, in an apartment in Montreal North in 2007.

A jury convicted Marseille on the weekend even though the boy's body was never recovered.

The judge said the conviction will stand, but he told Marseille that if he reveals where the body is buried, any evidence connected to the revelation will remain sealed.

Veteran lawyers say they've never seen or heard of such an offer.

"It's totally unusual," said defence lawyer Normand Boudrault.

It wasn't immediately known whether Marseille would accept the offer.

Nyagahene's mother said she found the offer acceptable.

"No one can keep a secret like that forever," said Liliane Muwamba. "If only we could lay a flower in his memory."

Possibilities

Immunity could help Marseille if his conviction is overturned on appeal and a judge orders a new trial.

Any evidence connected with the discovery of the body could not be used against him in a future proceeding.

Marseille, a known street-gang member, shot Nyagahene in cold blood at a party to prove his worth to the gang.

Partygoers agreed to help police solve the case, and investigators found DNA in Marseille's apartment as well as in his car.