I knew before this film that the justice system in the U.S. is far from perfect. and having watched it only reinforced that in my mind. As far as I know, everything that is said in the film is from a transcript of some kind. They are actual words, not inventions of a filmmaker with an agenda. While the filmmaker probably does have an agenda, that doesn't make the ideas and content of the film any less valid.
For me, this film could stand as the entire argument against the death penalty. Punishments are supposed to be about justice. Justice is not a system where six innocent people can be sentenced to die because of purposeful deceit or accidental human error. In reality there have been many more people exonerated from death row, but that doesn't make the argument any stronger. It should only take one death of an innocent to convince any rational person that this punishment is not morally sound.
