Make it so each clue has like parts and pieces that if you get them all, you can figure out the criminal.
Like, if someone runs over someone with a car, there can be broken bones laying around somewhere, and the license plate, then if you bring those 2 to the Police Office, you can put together the clues and get the person. Then you have to get an arrest warrant, THEN you can get them.
Though if a cop visually sees someone shoot someone in the face, then bang.
Just an idea though.