The story looks at twelve jurors about to make the biggest decision of their lives. All the evidence seems overwhelming that a Hispanic teenager killed his father after a violent argument. However, one of the basic tenets of the American justice system is "reasonable doubt." If there is any reason to doubt the evidence, then the jury must acquit the defendant, as there is no irrefutable evidence he or she committed the crime. In this case, the boy may have indeed murdered his father. However, so many details are left hanging in the prosecution that doubt exists in one juror's mind, and it begins to infect the others.
First, the film shows the diversity of the American people and culture. While the jury is all white and all male, the diversity of the men indicates the differences between people and their ideals. There are business owners, professionals, salesmen, and retirees on the jury, and like their professions, each one of them brings something different to the table and to the deliberations. Some are fair and open-minded, while others are racist, angry, and unreasonable. Each one has his own idea about the guilt or innocence of the boy, and each one must be convinced by Juror Number 8 to change his vote. Is this fair and reasonable? That is what the film wants the viewer to decide.
Part of the legal process, and part of the problem, at least according to this film, are the participants in the process. The judge has clearly served on the bench a long time, and seems disinterested and bored by the proceedings. The defense attorney seems to resent having to take the case as a public defender, and does not seem to make a good job of defending his client at all. Juror number 8 makes the observation that the attorney seems to have "resented being appointed" to a case with "no money, no glory, not even much chance of winning" (12 Angry Men). Thus, the boy is at the mercy of a system that seems jaded, burned out, and ev...