Goofs

When David finds the dead cat in the closet he turns off the light and closes the closet door. A moment later when Amy opens the closet door the light is on.

When David is in the bar after having his tire changed, the level of the foam in his beer glass changes.

When Amy gets back from jogging, the amount of and position of the sweat on her top changes numerous times from scene to scene.

The two Californian registration stickers on David's Jaguar E-Type's rear license plate at first appear on the bottom corners of the plate (which is in itself a goof) but in later shots appear on the upper corners, as is correct for California license plates.

After the fake hunt, the Sheriff asks David if his rifle is registered. In Mississippi, where the film is set, there is no state licensing or registration requirements for long guns.

After David runs into Jeremy with Amy's car, he was shown standing with his right arm outstretched parallel to the ground with a compound fracture of the upper arm, complete with the upper part of the bone protruding through his skin. A person with this kind of injury would not be able to hold their arm out that way since there would be no structural support from the upper arm; the arm would angle downward from near the point of fracture.

When David shoots the deer, he is standing in the open and the buck is looking straight at him. A deer in the wild would run off and not stand there waiting to be shot.

In one scene, Amy erases the "3" in the date on David's chalkboard and replaces it with a "4." In a later scene with Charlie, you can see that the "4" that Amy wrote earlier is now written in a different style.