Factual error: The motel's billboard advertised HBO, which did not exist in 1971 when the movie was set.
Factual error: In the final flashback scene, which was no later than 1971 because Nadine was still alive, the Ford van is a distinctive style not introduced until 1975.
Factual error: The movie is set in 1971, but a fire extinguisher with modern pictorial labels can be seen when the detective is dusting for fingerprints in the drugstore.
Factual error: When Bob is looking for a room downtown, he walks past a trash can with a modern plastic cover that was not available in 1971.