[Detective] - Knox's Commandments: 7# "the Detective cannot be the one to commit the crime" is one of the rules of mystery. If Conan wants to break the rule, then he has to give up on the ability to use investigative and communicative abilities for the night, where he performed the kill, and the upcomming day.
Conan has the perfect knowledge about crimes, and thus he may be able to erase every track of evidence that leads back to him. Conan's faction kills are undetectable, they remove the target's role from the write up and Conan receives their targets role, while their alignment and wincon are erased from history. Once Conan dies, all janitored roles will reappear fully.