Continuity mistake: When Dormer and Finch meet up after the interrogation, Dormer slams Fince against a metal support beam and the position of his hands of Finch change from being pressed against Finch's left cheek to being pressed against his neck/shoulder area as the camera angle changes. Happens about 3 times during scene.
Continuity mistake: When Robin Williams is being questioned by the police for the first time, one of the cops is talking to him. Very soon afterward the cop leaves the room and is walking away. We see the cop in the distance in another room, yet we hear the cop talking to Robin Williams again as Al Pacino shuts the door. Almost immediately, the camera angle changes to the cop as he finishes talking. He is standing in front of Robin Williams again.