Hello!
At first I wanted to make a list here with a good bunch of old point&click adventure games with detectives or private investigators (Sherlock Holmes, Tex Murphy and Discworld Noir games first things getting in my mind) that I'd love to recommend, but I imagine it's better to make this short an offer a concise idea:
A few years back I was able to play one of the Frogwares' Sherlock Holmes iterations: Crimes & Punishments, and one of the aspects in gameplay that I found very interesting was the case resolution mechanic.
I was able to find a video:
Looks like very doable: the player must connect the correct nodes (if he/she was able to discover the clues while investigating on site), and try to achieve a conclusion.The game story then diverges in case of your conclusions.
I hope this gives you ideas at least!
Good luck!
P.S.: Again, there is like A LOT of detective games if you look in the point&click adventure genre.