Mr. Monk Goes to Mexico - S2-E2
Factual error: Monk states that one of the reasons he suspected Dr. Maduro was because the doctor stated the amount of fluid in the victim's lungs in pints, which meant the doctor had worked in the US. But even in the US, the medical profession uses the metric system.
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.