Just so we're clear, if you suspect me of being Mafia, then I voted nitasu first on the second day, who turned out to be mafia. I doubt that any mafia would vote against his own team.
If you suspect me of being the serial killer, then I have no proof saying that it's not so, but if you lynch me, you'll lose a player that is not on Mafia's side, thus making your chances of winning slimmer. That is, of course, when I turn out to be the lyncher.
I would start looking at the players who haven't said much, like Prizmys or kraby. They could be Mafia trying to lay low, but then again that could be a horrible idea. Come to think about it, they're the only ones who haven't almost said anything. And we know that there's two mafia left...