Quote from Adrian Monk in Mr. Monk and the Genius
Adrian Monk: What did the paramedics say? Lieutenant Disher: Probable heart attack. Adrian Monk: He killed her. He said he would kill her, and he did it. Lieutenant Disher: Okay. Okay, there was no alarm. There was no one in the house, just the housekeeper and the cook. No signs of trauma or suffocation. Adrian Monk: Poison. Lieutenant Disher: No, housekeeper said she hadn't eaten all day, breakfast, lunch. Captain Stottlemeyer: So how did he do it? Adrian Monk: I don't know. I don't know.