Clues are a gameplay feature in L.A. Noire. They can be used as evidence and be used to push the boundaries with a Person of Interest. An example is using the reciept for a live hog to interrogate Frank Morgan while trying to find Adrian Black. Some clues consist of Weapons, Papers, and more.
There are useless clues and helpful clues. Useless clues consist of bottles, shears, litter and figurines.