I believe the Lt. speaks Italian in "Murder Under Glass."

And I just heard him speak Italian in "Identity Crisis."

That was a treat to hear - all of the TV versions of 'Identity Crisis' had that Italian exchange edited out.

This has come up before, and my take on "Strange Bedfellows" is that Columbo pointedly refuses to speak in Italian to the mobster, just to snub the mafioso's attempt to use Italian to buddy-up to him.

We know (and I personally don't think the writer forgot) that Columbo does speak fluent Italian. It seems to me that Peter Falk conveys this in the way he looks Fortelli in the eye while claiming he doesn't speak the language. His expression seems to say, "You of course know that I do speak Italian -- but only with my friends! I am a cop, you are a criminal -- and I do not consider you my paisan. Don't try that 'we are fellow Italians' stuff on me."