The Question and Answer section for 12 Angry Men is a great resource to ask questions, find answers, and discuss the novel.
This depends what the setting would be. Certainly a different culture might have a different context for the trial. Part of the suspense of the play was the pressure cooker-like atmosphere of the hot and humid room where the Jury was locked into....
That would be twelve men.
The young man was allegedly motivated by an argument with his father earlier in the evening.