In "Agenda for Murder" Columbo remarks to O. Finch about Ted Bundy being convicted and executed on the strength of bite-mark evidence. Offhand I can't recall Columbo referring to a "real-life" event like that. Even though that reference seems out of character for the Columbo series, "Agenda" is one of my favorite episodes ever for some reason.
Seems to me that also in "Agenda For Murder" (or was it "Identity Crisis"), there's mention of a country dropping out of the Olympics, which sounded like it was supposed to be a topical reference. But I don't remember whether that was a "real"-life event, or just something that happened in Columbo-World.