This Rp would take place in some vault, where a murder has occured. Characters would every and each one be potential murderers, and the CS's would contain some sort of characteristic that makes the characters a potential murderer. Then, when enough CS's have been gathered, a PM made vote would be initiated, where the Rp'ers vote for one of the characters(not their own) to be the murderer. The voting result would stay only in the knowledge of the GM and the vote winner, so that only two(or one if the GM's character wins the vote) people know the culprit of the murder, while the others have to find out who it is. The murder details would be tailored to fit the winning characters motives and made so that there are clues that indicate this particular character, but not too strongly. If a draw occurs in the vote, well, I'm still thinking on that.
I was thinking that there'd be only a few actual security characters investigating this murder, an overseer, and the rest are suspects trying to prove their innocence, the murderer included(who can, of course, be a part of the security as well or be the overseer besides being an usual vault dweller). The RP would naturally end when the correct murderer is caught, or if the murderer succeeds in destroying all the clues pointing at his/hers direction and frame another vault dweller to be the murderer.