I either blame it on my brother (because he's usually the one to start it first.) or just take the blame for it (even if it wasn't mine to deal with.)
For me it doesn't matter what happened, if I did it or not, I would always scream "I DID NOT MURDER HIM!!" then calm down and await my punishment XD
improvise baby :D
If it was true, I'd say I did it because I found it necessary to. It might've been selfish, but it seemed good at the time. Most likely I'd later on regret it.
I say I did it cuz I can pull it off.