If hatmoza has a reason he can't tell, then it is because he is the lie detector yes? Of course if he admits it then he loses his power. But I think (based on last time) me outing him would also have this effect. This could mean the mafia are throwing out a line and seeing if dtewi was/is the cop and hoping to get lucky.
This is based on a few assumptions on the lie detector role, and the thought that they are in the game. If I am fundamentally wrong about any of that then this line of reasoning is off and should be ignored.