Vanessa's ponytail reappears several times after being cut off.
The grandma's mobile home at the end of the movie is a late 1950s model. The movie shows the interior of a 1980s mobile home during the fight scene.
During the fight with Bob at the grandmother's house, Bob's hairnet falls off, but then appears back on his head in subsequent shots.
When Vanessa is attacking Bob in the caravan, she knocks down a plant and some other items, then she strangles Bob. However, when the detective goes to look at Bob's body, the plant has vanished from the floor, and the mess made around Bob is different.
When Bob and Vanessa are fighting in the trailer Bob fires off 19 shots. Bob appears to be wielding a .45 semi-automatic pistol with a standard magazine, which means it could hold 9 bullets (8 in the magazine and 1 in the chamber). Even an extended magazine (which would have been visible protruding from the bottom of the gun handle) would only hold 14 bullets maximum.
It is said that Vanessa is diagnosed with Antisocial Personality Disorder, but in the Diagnostic and Statistical Manual of Mental Disorders, this diagnosis cannot be given to anyone under 18 years of age. Instead, a juvenile is diagnosed with Conduct Disorder.
The address that Vanessa shows Bob has a 94132 zip code for Stockton. The zip code 94132 is really for San Francisco.
When Bob and his wife are interviewed on the TV, his neck injury halo is not screwed into his skull.
Vanessa's strangled grandmother's tongue moves when the detectives enter the trailer and the camera focuses on a close up of the "dead" body.
Obvious stunt double when Vanessa beats up Bob in the caravan at the end of the film. Her hair is different.
The late 1950s model trailer that the Grandma lives in is only ten feet wide. In the interior shots the rooms are as large as a roomy site-built house. An impossibility in only ten feet of width.
In the opening scene, Vanessa can hardly read the simple sentence "The cat drinks milk", but she seems to have no trouble reading the menu in the "Hi-Way Cafe".
Vanessa strangles Bob with his leather necklace. The problem is that he has had a tracheotomy. That procedure places a breathing hole low in the neck and Bob is seen exhaling cigarette smoke out of it from the restaurant scene. There's no way that her actions could result in asphyxiation.
When the officer goes back to the scene of the crime, he doesn't put on any latex gloves to avoid finger prints on the evidence.
When Vanessa shoots Bob, after he escapes from the vehicle, the first bullet misses (hits the ground). Then two shots hit him, but if you notice the right side of his blazer, a third shot hits him but there's no sound.
When Vanessa enters the Hi-Way Café, as the glass door closes behind her, the reflection of a boom operator holding up a long boom pole is visible.
During the daylight shots of Vanessa and Bob in his car, shadows of camera equipment appear on the car's hood.
Vanessa is surprised when she sees the car door has no inside door handle. However, earlier in the film, she and Bob stopped to eat at a restaurant. She should have noticed the missing door handle then.
After Vanessa shoots Bob four or five times in the woods, he somehow walks into a hospital ER room.