What a solid little mystery! I really like your presentation on this one. Detective Vision is a great addition to help prevent pixel hunting. I like the red herrings strewn throughout the mansion, though the game would benefit a lot from a few more characters to be suspicious of. There's also only the one inventory puzzle (use key), before using the Judgement Gun to accuse the murderer, meaning it's an underused mechanic. I like the evidence summaries, though it would be cool to present evidence to characters to see if they respond to it with new clues.
Also thank you for including a run button. It was well appreciated!