Apparently this is the movie that re-wrote the book on documentaries: Errol Morris tackled the case of a man on death row who didn't commit the crime he was accused of, and in the process changed documentaries forever. There isn't a word of voice-over in the entire thing: just talking heads and some basic re-enactments. It's a hell of a lesson in how badly astray justice can go when cops want to catch a cop-killer ... and willingly turn to someone complicit in the crime for "evidence."
At the centre of this is Randall Adams. On a weekend in Dallas his car ran out of gas, and as he's walking with the gas can, a young man (David Harris) offers him a ride. He and the young man hang out for a while, watch a movie. This much all parties agree on, although Harris puts the events later in the day than Adams. Late in the evening, a cop is shot and killed while approaching a car on a routine traffic stop. Randall says he and Harris had parted ways a couple hours before that happened, Harris says it was Randall driving the car. Morris builds up a series of stories that eventually make it very clear that the police department and the judge had made a decision before the trial began and the wrong man was convicted. The witness you would most hope would tell the truth - the dead cop's partner - appears to have been lying because she was supposed to be out of the car ready to defend him (she claims she was) but was actually in the car drinking a malt. So she's lying through her own guilt. The film was clear enough about what actually happened that Adams was eventually released - although no apology was ever heard from the state of Texas.