Case Closed (1996)

Season 14

Episode 26: The Mystery of the Half-Completed Crime

Kogoro is invited by the producer of a detective show to share his stories. While he's there a murder occurs. The victim is one of the two main script writers for the show. The main suspect is a newbie third writer who brought the coffee to the producer and scriptwriters. The victim hated the him and has tried to get him fired from the show multiple times, so the motive is easily established. The only problem is figuring out how he got the victim to pick the poisoned coffee. In the end they realize that the suspect didn't use a trick at all; he didn't care which one of the two scriptwriters drank the poison.