Just an idea: 1 cop claim D1, kill your report to check your sanity, whisper everyone a random password and tell those password to your cop partner tomorrow your partner can proves himself by outing passwords. And without getting hooked. Of course maf job is to find the other cop, hook him and kill the claiming cop.
also mafia, I spec'd some games and never seen cop giving passwords, if cop didn't give passwords feel free to cc cop and prevent having a clear to lead in D2.