Mr. Monk and the Panic Room - S3-E2
Factual error: Disher hands Stottlemeyer a pistol and tells him that he just unloaded it, but Stottlemeyer just takes his word for it instead of double-checking it. You NEVER, under any circumstance, take anyone's word that a gun is unloaded; you always check it yourself. As a police officer, Stottlemeyer would know that.
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.