Metagaming...

[Dead Rikimaru]

Metagaming is like checking the criminal antecedents of a person.
When there is a murder in real life the criminal background of the suspects tells a lot about them.
Of course the fact that someone committed a crime before is not proof that the same person committed the crime in question, but there is always a high probability and that's why it's always verified in real life, with good results.
I see no reason the same shouldn't be done in mafia games.
That said I'd say metagamig makes the game easier and that's why I prefer to play with different people every time.