Dale Kingston in Suitable For Framing for the win. I think one of the things that makes this episode stand out is that Dale is caught red-handed and humiliated in front of his aunt Edna whom he tried to frame for the murder. Dale's reaction is priceless. I also really enjoyed Candidate For Crime. All Nelson Hayward can do is stand there with that "I'm finished" expression upon his face while Columbo exposes him. Harold's tantrum reaction in Playback, realizing that his security system was his undoing (I guess it really did work after all).
That has got to one of the best!. And Ross Martin played such an arrogent and hateful character. It was a great joy to see him reduced to a stuttering buffoon at the end.
This was another double burder where thexsecond murder goes unprosocuted [at least on camera]