Third of four appearances by Patrick McGoohan as a murderer in the Columbo series. The other episodes are: By Dawn's Early Light (1974) (as Col. Rumford), Identity Crisis (1975) (as Intelligence agent Nelson Brenner), and Ashes to Ashes (1998) (as funeral company owner Eric Prince). Moreover, McGoohan directed this episode.
Columbo figures out that Paul Mackey used to smoke cigars. One of the clues Columbo says he noticed was Mackey's "behavior". This is likely a reference to compulsive snacking, which is something that an entirely different character does throughout the episode. This is probably a result of some script rewrites.