Continuity mistake: When Tuffy's son is killed, you see his shoe fly by the camera, with his severed foot still inside. Shortly after, when you see the shoe again, it is empty, and simply covered in blood.
Continuity mistake: When Nisha is talking with Clayton outside his house she leaves in her car and closes the door twice.
Other mistake: After the Joker has become a vampire, you can still see his reflection in metal poles and such while he is chasing Batman in the bloodbank. (00:47:00 - 00:49:00)
Continuity mistake: During the chase after John witnesses a woman get kidnapped, one of the thugs shoots out of the driver's side headlight of his blue van. A couple of shots later, the headlight is back in and it's there for the rest of the chase.