Character mistake: Columbo explains to Hayward (the killer) how the accepted version of events is impossible, because when he was shot Harry Stone was standing in a dark garage and the killer could not have angled the headlights of his car in such a way that he was made visible (in order to be shot). But neither he nor Hayward even consider the possibility that the killer could have been carrying a torch, which would not only have illuminated the scene, it would have dazzled the victim and hidden the shooter.
Character mistake: Art expert Dale Kingston describes Goya as 'the penultimate artist'. "Penultimate" has nothing to do with greatness or artistry, it means second to last, and nowhere during his speech does he indicate that Goya is 'second to last' in anything to do with the discussion. In the context he uses it the word is completely meaningless.
Character mistake: Adrian Carsini, a wine connoisseur and winery manager, pours two glasses of wine, one for himself and one for Lieutenant Columbo. Each man puts his hand around the top of his glass and begins to drink. A true wine connoisseur never touches the top of the glass. He holds the glass by the stem so the warmth of his hand does not affect the taste of the wine.
Character mistake: A valet tells Columbo that automobiles belonging to Sauri embassy personnel are repaired at a service station two blocks away. Later, when Columbo is speaking with Hassan Salah, he says, "I know your cars are taken to a service station three blocks away."