Mr. Monk is the Best Man - S8-E13
Randy Disher: I think somebody's trying to scare you.
Captain Stottlemeyer: Yeah, but why? I mean, it doesn't track. If the guy wants a piece of me, if he wants to hurt me, why doesn't he come at me? What's all this cat and mouse crap?
Disher: So who's on your short list?
Stottlemeyer: I've been at this all morning. Most of these guys are either in jail or dead.
Disher: Or both.
Stottlemeyer: No. Nobody is both.
Answer: Notice also that in the opening credits scene when he is touching parking meters her also wipes his hand on his clothes each time he does it.