I think the moment Columbo really starts to focus on Nora is when he concludes that Jean was the target. The clue about the tire not going flat and the murderer letting out the air and taking the time to put the cap back on is what made Columbo realize that the murderer wanted Jean and Jerry to switch cars. Nora is the prime suspect because she is the only one who knew where Jean was going to be that night, and Nora is also the only one who really knew Jean.

Jerry is an opportunist of course, but I can never help thinking that he really had feelings for Jean as well, mainly because of that look he has and that voice he speaks in at the restaurant, when they're breaking the news to Nora. Mel Ferrer really sells you on the idea that it's a real blow to Jerry.

I really don't like Requiem For A Falling Star like I like other episodes. Columbo always plays his cards close to his chest and probably realized Jean was the target a lot sooner than he voiced the idea. But the reason I don't like Requiem is that, and this is easy to forget, perhaps, once you've seen the episode a few times you are meant to believe, until that moment where Columbo makes his reveal, that this was a mistake.

The problem is that once that reveal is made the lengths they went to fool us start to look a bit messy. I mean, for example, she actually fainted, and then she spent the whole night in hospital because of the fact. Actress or not that's a lot of healthcare professionals she seems to have managed to con.

This is one of those episodes where Columbo does a deep psy-op test on his potential perp right out of the gate. With Nora, his test was the following, and I believe was the moment he was really on to her.

If Nora is innocent, and had just recently learned of the horrific way in which her beloved secretary had died, she is going to behave and react in a certain way to Columbo's questioning. When Columbo rains-down praise on her when he enters her home at the studio, she responds in a way that tips her cards by presenting a demeanor to Columbo that she isn't really all that traumatized. "Never thought you'd meet a legend, right?..", etc.

Then, of course, Columbo doubles-down (verifies) this test by asking her to call his wife for a chat, out of the blue. Weird right?

Well, we all know if Ms. Chandler was actually innocent, how she would have reacted to a random detective's request for her to actually pick up the phone right there and CALL some unknown person for a chat about nothing, in the midst of such awful circumstances. She's snap at Columbo for asking such a crazy thing right there, and tell him to get to work trying to find out what happened to her secretary. But, she actually plays along with Columbo's bizarre request, leading him to believe she may be on the other side of innocent.