"They arrive with calcified prejudices and hardened hearts, testosterone positively steaming up the windows."
One room, one day, twelve men. It's the hottest day of the year. The men are charged with deciding the fate of a young teenager who has supposedly killed his father. The jury reaches a verdict: eleven vote guilty, one votes not guilty. It's a hung jury.
Over the course of the day, the dissenter manages to sow seeds of doubt in the minds of the other jurors. The vote is recast over and over. If declared guilty, the accused faces the death penalty. His fate rests in the hands of "twelve angry men".
In 1954, Rose Reginald served on a New York City jury in a manslaughter case, his inspiration for Twelve Angry Men. He explained: "[The] moment I walked into the courtroom...and found myself facing a strange man whose fate was suddenly more or less in my hands, my entire attitude changed." (http://www.encyclopedia.com/article-1G2-3420700025/twelve-angry-men.html)
Reginald wrote a play for television in 1955. Two years later, a film premiered, starring Henry Fonda. A stage play followed, debuting in London in 1964.
Twelve Angry Men movie scene circa 1957 courtesy http://jasoncollin.org/2013/09/01/12-angry-men-1957-movie-review-recommended/.