I've seen all 69 episodes multiple times and for some reason this one is one of the dullest of the group. Ruth and Janie were just......... B O R I N G! I ...just....really... didn't ... care. I liked Columbo's questioning of the light switch.
I like how you say that many killers on Columbo are "marksmen". That's both very funny and true!
Here's the thing that gets me about this episode, Edward is doing the inventory by listing the pieces they have on a tape using a microphone. Why then, does Columbo not hear the first shot when he's listening to the tapes later?