Factual error: When Amy tries to escape from Mort in her car, there is a shot showing her feet trying to hit the right pedals to get the car moving. Her car is a SAAB 9-3, but the shot from the footwell of the car is not a SAAB.
Factual error: When Amy tries to escape from Mort in her car ,a SAAB 9-3, she starts the car with the gear in neutral (the car has manual gearbox). The ignition key of a SAAB can only be inserted with the gear in reverse.
Factual error: At the climax, Mort stabs Amy in the lower leg. She stands up and leaves a prominent bloody footprint on a stray piece of paper on the ground. Problem is, there's no way the bottom of her shoe could be covered in blood to leave the footprint. She's been bleeding for less than five seconds, and there's no pool of blood for her shoe to pick up and make the footprint with.
Factual error: At the end when the cornfield is revealed, it is in full shade, surrounded by fully mature trees. For corn to grow well and produce, it has to he planted in open fields with full sun exposure.