I agree with gman, I didn't want to say this in a straightforward matter.
But you're the innocent guy here, and friends....well let's just say everyone who is doing the same degree as you in the same timeframe is your competitor, so knocking 1 person out of here means you're better off.
Still though, you're losing 11 marks mate, that's real hefty, and too costly for just a friend. If your buddy has a shred of honour and decency (as a friend) left in him, he should have the guts to walk up to the lecturer and confess.