3 assassins is kind of too easy. We should assume 4 assassins and go with the 1 mislynch strategy.
If you're the cop and you got an innocent, contact your innocent and tell him to out himself as your inno, and he can lead a lynch. Guardian protects the inno.
If you're the cop and you got a guilty, out yourself as cop and point at your guilty and the guardian will protect you.