Deliberate mistake: Though the film takes place over the course of several weeks, at night there is always a full moon.
Deliberate mistake: A branding iron loses its bright orange glow relatively fast when it's out of the fire. When the police enters the room it is still very bright orange even though it has been on the floor for some time.
Deliberate mistake: When Janine smashes the mirror she takes it directly off the wall and raises it above her head, and the reflective side would be facing behind her. The camera immediately cuts to a front view as she's throwing it down and the reflective side is in front. This was probably done for dramatic effect so that the reflective side would hit the ground first.
Deliberate mistake: John is shown repeatedly studying Lucinda's numbers and even copies them to a whiteboard, and yet when Diana notices the backwards EE at the end, he's surprised and obviously acts as though he hadn't noticed them before, straining credulity, since he had just as obviously obsessed over the numbers and couldn't have missed the letters beforehand. (01:08:40)