(I don't think there are any major spoilers below that would ruin the show, but I do reveal some Columbo plot.) Okay, fine, Last Salute to the Commodore is an

(I don't think there are any major spoilers below that would ruin the show, but I do reveal some Columbo plot.) Okay, fine, Last Salute to the Commodore is an exceptional case; it's widely regarded, along with the two later Ed McBain ones, as way out-of-character for the show. Usually when he confronts a character who has something to hide but isn't the murderer, he's over-the-top friendly and apologetic, like with the affair in Columbo Goes to College or the victim's bride in Double Shock. There are probably some better examples. Yeah, the usual formula is that the culprit tries to demonstrate innocence by helping with the investigation until Columbo gets too close, and then abruptly shuts up. I think that mostly speaks to Columbo's style, though; it's realistic that a murderer would do one or the other given how they're being questioned. I'd still maintain that the biggest weakness of the show is that Columbo almost never has the wrong suspect, and sometimes he has the correct suspect far too early (why does he read the palm in Death Lends A Hand?).