1. I know Columbo is „not-so-much-blood” series, but here it is a little too far. Three shots, body was moved, and no blood at all
2. She probably planned that for long time if she had a used bulb prepared :)
3. Maybe this is a stupid remark, but I can't help it: everytime when Hamilton is arriving at Chadwick's residence (in the beginning, while the murder is happening), it reminds me about Frank Drebin, and why? Because of his passenger seat in the moment of arrival. Did you notice its movement? Looks like a part from The Naked Gun for me
4. I like the scene with Columbo on the ladder when the dog comes. He says „easy boy”. Dog is still barking. Then Columbo says „that's right” but the dog is still barking :P and his reaction for „take my luggage”. I mean his face expression :)
5. When Columbo brings the luggage inside, you can clearly see that the background outside behind main door is completely different than it should be. But this is very common thing in most of Columbo episodes
6. One time I will have to count the amount of „people do unexpected and irrational things when they are in shock” which is a basic explenation for Columbo many many times :D
7. For me the best scene from this episode is in the courtroom. When a lady talks to Columbo about Jupiter and Pluto. In those moment I appreciate so much Peter Falk's acting
8. When Columbo and Peter are in drive-in diner, I noticed that Hamilton is quite carefully checking his hamburger and then never eats it. So I guess he was not the fan of Columbo's choice :D
9. After so many viewings, I pay attention for really detailed things sometimes. Now I noticed that when they leave hairdresser the carpet is red, but when we see them leaving this room (and entering reception room) from the other side the carpet changes the colour for something close to grey
10. What a marvellous thing: having a pool table and a bar (!!!) in the clothes store! Is it still like this in US? :) and by the way: the assistent buyer lady is the nude model from Suitable for Framing, right? At least I think so
11. In the end Columbo says „my wife said – you put the cart before the horse, and in this case the horse is before the cart”. Shouldn't has he said: „in this case cart is before the horse”?
12. How is it in US? If the court made the decision that it was an accident, and Columbo proved it was not – can she be tried again?

..."5. When Columbo brings the luggage inside, you can clearly see that the background outside behind main door is completely different than it should be. But this is very common thing in most of Columbo episodes"...

Yes, in earlier episodes I like how in later episodes they use real locations and real houses interiors. One of the few shows that did that. There's even a map showing all the location shots..

https://www.google.com/maps/d/u/0/viewer?mid=1jcy9YcfVzQwjdcn1PkcA9gzHIRAkdLSH&ll=37.6771906516847%2C-112.12997472783742&z=5