just in case the mafia has thought of this idea i will say what i have seen as possibility's that they could do.
1. claim to be x night cop and claim one of their member is town cause there can be cops who have same night
2. claim to be x night cop and town being lynched is town to give yourself credit
3. claim to be x night cop and claim random town is town to give yourself credit
and here is best way to counter it (if able) real cop investigates the claimer during the time they can
and good luck to all doctors cause that is just wild guessing with 2 thing against you being choosing town and being the kill for the night