Of course you can tell when someone is vanilla MaD. There are many scenarios where people unknowingly show what degree of importance their role has. However, I'm not going to explain this...it's a fairly obvious thought process.
This thread needs more life though. I really suspect one of the inactive players who bandwagoned on me to be the Killer Captain. The Killer Captain knows, that even if his teammates die, and he survives, it's all good, since he's the Killer Captain, and with his killing ability, he's strong as hell, as long as he's alive. This doesn't rule you out MaD, but yeah, I was just testing to see your reactions earlier. They probably weren't very favourable to clearing you, but still, I don't think you'd be this active if you were the killer captain. You'd probably be wayyyy more cautious.
I'm also going to predict that the Killer Captain tries to kill someone I suspect and put the blame on me since I'm a captain too. Because, if my major suspicion is right, that's the way this person has played in previous games.