This episode was just mediocre in my opinion. Although, when Columbo excuses himself from the table and realizes that "these two know each other," he is very, very clever in not letting them know that he suspects something. (Incidentally, Kathleen was played by Peter Falk's wife).

Yes I agree. Its part of one of the newer Columbos, which, while still quite enjoyable, arent as good as the early years. The new ones I enjoyed most was Rest in Peace Mrs Columbo and Columbo Cries Wolf. Incidentally there is goof in A Trace of Murder near the end, when he is showing the cigar butt to Patrick in the small plastic bag near the courtroom, in the seccond shot the bag has mysteriously switched to Columbo's other hand !

I for one think this is a very good episode. Trap set, implied confession at end with Kathleen going to D.A. Good debunking of phony clues for frame-up. Both suspects' goofy reactions to Columbo's idiosyncracies. Fun Columbo interactions and dialogues not only with Clifford's wife and forensic guy before full suspicion, and with colorful Clifford.