"12 Angry Men" is a 1957 film based on a play by Reginald Rose
This film puts an interesting twist on the courtroom drama by setting (almost) all of its story in the deliberation room, where the 12 anonymous jurors decide the fate of the defendant. The defendant, a young man living in the slums, is being accused of murdering his father. If found guilty, he would be sentenced to execution.
An unanimous vote by the jurors is needed to decide a verdict of either guilty or not guilty. They take a preliminary vote, and all but one are prepared to find the defendant guilty. Juror #8 (played by Henry Fonda) is unsure :
We're talking about somebody's life here. We can't decide in five minutes! Supposing we're wrong ...
Aside from the excellently-executed plot -- containing courtroom drama staples such as logical argument and analysis of evidence and testimony -- the great thing about this film is the presentation of the jurors' characters. As the 12 angry men argue over the case, each bring their unique background and experiences to the conflict.
Besides Fonda, the film stars Lee J. Cobb as Juror #3. Sidney Lumet's directorial debut on the big screen garnered him an Academy Award nomination. The film was also nominated for Best Picture and Best Adapted Screenplay.