When Columbo searched (or "looked") in Dr. Kepples office a defense attorney would have a field day with him regarding this. No I'm not a cop obviously but I consider all that an illegal search.. No warning, no warrant, no permission to search the premises. I mean I think it's bogus but then again I'm just throwing it out there for opinions

I guess we can assume that the search would be legal because Columbo really wasn’t searching or even “looking”. He was merely posing as someone who was searching. He didn’t open up any drawers, closets, etc. I don’t know how this would work in real life, but it was reasonable for my suspension of disbelief.

That was also the crime scene, which would give him more latitude than going to the Dr's house for example. He wouldn’t need a warrant to take photos in the building of the crime scene.