Robert Redford was originally involved with this film. After writer David Mamet delivered his draft, Redford was uncomfortable with the main character and hired another writer to do another draft, and so on until Redford decided he didn't want to do the film. He was uncomfortable because he did not want to play an alcoholic. Sidney Lumet was offered the project. He read all the drafts and identified the original Mamet version as the one to make. At that point, Paul Newman agreed to star.
Among the people in the courtroom during the dramatic closing speech is a young Bruce Willis.
David Mamet's draft was rejected at first because he refused to put the outcome of the verdict into the script. It was director Sidney Lumet who convinced him to alter his ending.
After the verdict was announced in the film, director Sidney Lumet filmed two versions of the ending. In one version, the final shots we see are of Newman's character walking away from the courtroom in a series of long shots, never seeing what happens after he leaves the courthouse. In the version that was used, we see a sequence after he leaves the courthouse.