Revealing mistake: In the jazz club, the saxophone player's finger movements don't match what he is playing.
Plot hole: *SPOILER* Toward the end of the movie, Ryan Gosling goes to Hopkins' house where Hopkins is tricked into not only confessing again, but giving Gosling the murder weapon, after they are back in court and Gosling is the acting prosecutor. This would be a conflict of interest due to the fact that Gosling is a witness.
Suggested correction: First, the gun that Beachum took from Crowford's house was not the murder weapon. It was Crowford's unfired gun. He only took it out of the fear of his life. Second, Beachum entered Crowford's house with police supervision. If he plays it by the book, Crowford's confession is valid. In that case, supervising officers will stand witness, along with a recording confirming their testimony. Third, Beachum doesn't need the confession anymore. He was amply clear on that matter.
Factual error: The license plate on the blue Ford Taurus is 674-H2T. Format for New Mexico standard issue yellow plates is 123-ABC (three numbers, the Zia sun, followed by three letters).
Continuity mistake: In the opening scene, the car's shadow changes with each shot from very long to very short.
Other mistake: Chris' leg cast was thigh-high. When he got out of bed (and used crutches), his cast was OVER his pants. His pants' leg did not appear to be cut off - it was securely under the cast and never changed despite all the fighting/activity he engaged in. (00:36:22)
Factual error: Although B. B. Rush's wears the rank insignia of a Specialist and he is addressed as Specialist by his interrogator, all the documentation shows his rank as Private First Class.
Factual error: The Mustang used to take Sylvia to her parents at the circus when she escapes is a 1967. The scene is set in 1965.