Gaffes

When Jennifer is moving in and opens the toilet for the first time, the water is dark brown. When she drops her cell phone in it the toilet water is significantly cleaner.

When the rapes are finally over and Jennifer manages to get up, she is filthy and covered in leaves. Later, after she has walked away and is staggering through the woods towards the bridge, she is practically clean.

When Jennifer is trying to get the wine out of her sweater, she scrubs it furiously, but when the scene switches and she is visible through the lens of the voyeur's video camera, her arms are barely moving.

When Storch confronts Stanley with the tape delivered to his house, he holds it with the bottom of the tape facing Stanley; in the next shot the bottom is facing toward Storch.

When the girl gets to the cabin in the opening scene, she opens a bottle of red wine. In the very next scene she is drinking white wine. And in the scene after that the wine is red again.

Louisiana has parishes instead of counties, so there's no county sheriff.

When Earl and the Sheriff go quail hunting, Earl is carrying a hunting rifle that is not used for quail hunting.

Sheriff Storch's police car does not have a partition between the front and rear seats, allowing Jennifer to assault him from the back seat. This is the exact thing partitions in police vehicles are there to prevent.

67 minutes into the movie, a dart board is shown on the sheriff's living room wall near the ceiling. Unless there as decoration, the board is over two feet higher then regulation.

There is no powder that can make water as acidic as it was made when Jennifer puts it in the water.

(at around 1h 30 mins) During Johnny's torture scene, his real teeth are visible above the fake ones.

While Jennifer is torturing Stanley and zooms the camera and says "Smile pretty for the camera," someone is visible behind Stanley behind the trees.

When Storch goes home and talks to his wife, a transmitter is clearly visible under her shirt when she turns her back to him.

When Jennifer is freaked out by sounds in front of her cabin, she goes outside to look. When she comes back in, she locks the cabin door and starts walking towards the stairs/living room. The faint reflection of camera/crew can be seen in window in the background.

The toilet water should be clear when Jennifer goes to check it after the tap water runs dirty. It should only be dirty after a flush, which she specifically states she cannot do.

Storch returns the cabin keys to Earl, implying that the cabin has been locked and secured; a few scenes later, Matthew is seen inside the supposedly-locked cabin.