Well, as Columbo, himself, said in at least one other episode...even with circumstantial evidence...he thought the jury would convict because of..."means, opportunity, and motive".

Don't forget Columbo was pressuring the younger woman who was already caught in lies because of the phone records.

(I think 2 of the most surprised and expressive reactions Columbo had in the entire series includes the scene here where he finds out that the younger woman is the daughter and in Swan Song, when he finds out Johnny Cash/Tommy brown had been a parachute rigger in the Air Force.)

As for Any Old Port...our stories end with "How's he gonna catch them?"

As soon as you alter the script which was used, you need to compensate with something else. I suppose we could second guess the "legals" until H*e*l*l* freezes over.