I'd have to go with the "Press X to not die" thing, but with a twist! I'll leave a Playstation controller next to the victim, find myself a really good vantage point, then proceed to kill everyone who touched the body, but did not press X beforehand with a semi-automatic sniper rifle. I'd also pre-emptively have a Playstation controller next to me, and a piece of paper with "Press X to not die" on it too, in case I get taken down by the police with lethal firepower. I'd also make sure that I got some sort of escape plan after 15 minutes or so, and then I can repeat the process elsewhere. It would be brilliant(ly sickening)! xD
... and if I survive and it goes to court, I'l immidiately plead insane, while shouting and rambling about how there is someone out there controlling my every move, and that he did it. I'm just the personification of the players evil acts! I can't be held responsible since I'm a controllable character in a massive game or something!