Joyce Van Patten is one of them, Robert Culp is another depending on whether "Columbo Goes to College" is late 90's.

Robert Vaughan might be another one, I never watched all of "Last Salute to the Commodore".

Oh, Clay, I've slipped up, Joyce VP is a third one. Oops!

No, Columbo Goes to College is one of the modern ones.

I am sticking to the sixties and seventies episodes for this.

Could Fred Draper be one? I am terrible at names, but wasn't he the murderer in "Commodore," and also (heh) in "Fade into Murder," but NOT in "A Deadly State of Mind"? Sorry I don't remember years, so these may be outside of your parameters. Neat and intriguing quiz question, though!

From the replies, it looks like I might have forgotten some of the murderers who did play other roles.

hehe Hey, that makes it even more fun - it is a mystery even to you! *grin*

In the 70s version, Patrick O'Neal is the only one who holds the status of having played a guest killer *first* ("Blueprint For Murder") and then when he returned again it was in a "demoted" role ("Make Me A Perfect Murder"). This is in contrast to Robert Vaughn, who was serving the role of red herring when he appeared again.

Ray Milland of course graduated from important supporting role in "Death Lends A Hand" to killer in "The Greenhouse Jungle".

Hm I'd say Patrick Mc Goohan who only plays aa a murderer.

About Joyce van Patten (the murderer in "old fashioned murder", right?), she doesn't play only as a murderer, because in "Negative Reaction", she plays the religious sister who believes Columbo is a beggar.