Twelve jurors retire to the jury room as a murder trial concludes. The charge is murder in the first degree, and the judge reminds the jurors that they must base their unanimous decision of “guilty” or “not guilty” on whether or not there is “reasonable doubt” in their minds as to the guilt of the accused. The accused is a youth from a poor urban area who is on trial for killing his father with a switch knife. The jurors converse as they settle into the jury room: Seven offers chewing gum and complains of the heat, Five is surprised that the Guard locks the door to the room, and Twelve worries about missing his job in advertising. The jurors discuss Four’s hand-tailored suit, and the Foreman offers a story about his uncle, a tailor, who once served on a murder trial where the accused was acquitted. Years later, the Foreman says, the man was discovered to be guilty, after all. Three complains that the six-day trial could have been finished in two days, and Seven agrees, stating that “that business about the knife” was the phoniest story he ever heard. The youth claimed he lost the switch knife, which he was known to have purchased, on the night of the crime.
The Foreman calls the group to order, and Seven hopes the proceedings will be quick, as he has tickets to a Broadway show that night. Ten says that it probably serves the dead father right for letting his kid run wild as all those “kind of people” do. The group decides to vote immediately to see where they stand. Seven hopes they might already be in accord. They vote by raising their hands. Everyone votes “guilty” except for juror Eight who votes “not guilty.” Three is surprised as this and says that one could tell the boy was a murderer just by looking at him. Eight asks him where one looks to see if a man is a killer. Eight says he voted “not guilty” because there were already eleven votes for “guilty” and it’s not so easy to send a man to his death without discussing the trial first. Eight points out that the boy had a terrible life growing up, and he feels the kid deserves their deliberation. Ten disagrees, saying the kid received a fair trial, and that the jurors don’t owe his kind of untrustworthy people anything. For the first time, Nine, an elderly man, speaks out in protest, saying that no group of people is more or less honest than any other. Eleven closes the window, but Seven wants it open. Eleven, an immigrant from Europe, is quickly bullied by Seven into reopening the window and finding a different seat. Three and Four retrace the boy’s story. The old man who lived on the floor below heard the boy yell, “I’ll kill you,” and then heard a body fall to the floor. He hurried to his door and saw the boy running down the stairs. The boy claimed he was at the movies, but didn’t have a ticket stub and no one there remembered seeing him. The woman across the street saw the stabbing through the windows of a passing elevated train. Eight asks Ten why he believed the old man and the woman’s testimony when he’d already stated that all “those people” were dishonest.
Juror Three brings up his own son from whom he is estranged. He feels that all kids will break one’s heart through disobedience and selfishness. Four and Ten feel the kid’s background is against him, but Five points out that he himself grew up in a slum. He grows angry, feeling that these statements are personal attacks against him.
The jurors discuss the switch knife, the murder weapon, and ask to have it brought in because it is distinctive in appearance. Eight says he feels it is possible that someone else killed the father with a similar weapon to the one the boy purchased. As he claims this is possible, he reveals a second knife he has that is identical to the first. He purchased this knife in a shop near the crime scene. Eight proposes a vote by secret ballot. He says that he is willing to concede his doubt and vote “guilty” if all the other jurors feel that this is how the jury should vote. The other eleven jurors cast their votes. There are ten “guilty” votes and one for “not guilty.”
Three and Seven are furious that someone changed their vote, thereby prolonging the jurors’ deliberations, and demand to know who did it. They immediately accuse Five, but Eleven stands up for him, saying that he thought it was the purpose of the American system to protect those with “unpopular opinions.” Nine offers that he was the one to change his vote. He points to Eight’s courage in standing alone, in asking them to listen and deliberate further, as the reason for his changed ballot.
Two and Four, at the water cooler, wonder about the meaning of “beyond a reasonable doubt.” What evidence do they need to support a “not guilty” vote? Do they need evidence of the boy’s innocence? Three tries to start a game of tic-tac-toe to pass the time and Eight says that this is not a game, and reminds them all that a man’s life is at stake. Eight begins to explain his “feeling” that the testimonies of the old man and the woman don’t seem right. The jurors consider the length of time that it takes for an elevated train to pass and how deafeningly loud such trains are. Eight wonders how the old man could have heard the kid yell, “I’ll kill you!” over the sound to the train. Three wonders why the old man would lie and Nine points out the quietness and poverty of the man. He says the man might have needed attention so badly that he would “make himself believe” something he didn’t know for certain. Nine says that he speaks from experience.
Eight questions whether or not the kid would yell, “I’ll kill you!” out of anger or because he plans to literally kill his father. He points out that many of them have said such a thing, with no plans to do so. Five chooses to change his vote to “not guilty” because he thinks there’s a doubt. Five questions whether the old man could have “run” to the door, as he moved slowly in court and used canes. The jurors ask for the diagram of the apartment layout to determine how far the man’s room is from the door. The old man said it took him fifteen seconds to get to the door. Eight recreates the old man’s movements by pacing out a space in the jury room. Juror Two times Juror Eight as he pretends to get up from a bed and move through the space. It takes thirty-nine seconds. The jurors acknowledge that there is quite a discrepancy between this and the old man’s testimony. Three is furious and accuses Eight of acting out of sympathy for the kid. Eight says to Three that he wants the kid to die and that he is not considering the facts. Three lunges at Eight shouting, “Shut up! I’ll kill him!” as he is restrained by two others. Eight says to Three, “you don’t really mean you’ll kill me, do you?”
Four feels that the others are behaving like children and letting their emotions get the better of them. Eleven says that the beauty and power of the American legal system is that it attempts to achieve unbiased decision-making, and that the jurors should not make a legal decision into something personal. The jurors do another round of voting. They are evenly split: six for “guilty” and six for “not guilty.” The jurors wonder whether they should announce themselves as a hung jury so that the boy will be retried with a different set of jurors. But Eight feels that they’ll be able to reach an accord. The jurors vote on whether or not they are a hung jury, but this vote is also split evenly. Two explains that he changed his mind because Eight was calm and confident and Three was angry and insulting. Four points out that these considerations do not change the guilt of the accused.
Four begins to make a series of counter-arguments to Eight’s claims. He demonstrates, by the same timing method, that it would have taken the killer longer than fifteen seconds to ran past the old man’s door. Perhaps the old man was wrong about how long it took him to get to the door, but right about what he saw? Two and Five change their votes back to guilty. Eleven points out how dark it was in the tenement building when the jurors went to visit the scene of the crime. He wonders how anyone running down the stairs could be identifiable. Eleven asks Seven if he really feels no doubt about the case, and then says he must not understand what “reasonable doubt” means. Seven is immediately upset that someone fleeing from another country could come to America and tell him about right and wrong and how things work. Four silences Seven by saying that no one is asking where anyone, or their fathers, came from.
Two raises something that has been bothering him about the case. The stab wound appears to have been made downward from above, as if the attacker was taller than the victim. But the boy was not. Three demonstrates, by holding the knife and stabbing it toward Eight, how a downward wound could be created by a shorter person. Eight points out that the boy was an experienced knife-fighter, who was already in trouble for this activity. Five suddenly realizes that among the knife-fights he has seen in his life in a troubled neighborhood, switch knives are always handled underhanded. An experienced knife-fighter would not disobey this rule in a moment of peril and emotion.
Eight demonstrates that for the assumption of “guilty” to hold, one must suppose the kid was smart enough to avoid making an experienced knife wound, yet dumb enough to murder his father in front of a passing train of witnesses, smart enough to wipe his fingerprints from all the doors and the knife, yet dumb enough to not invent a decent alibi. The impossibility of these contradictions convinces everyone, except Three, Four, and Ten. Ten bursts out that such people are never innocent and that they don’t value human life. As he speaks, several of the other jurors rise and walk to the window, turning their backs on him. Four tells Ten to not speak again. Four says he still will vote “guilty” because of the testimony of the woman across the street. The jurors recount her testimony until they realize that she was wearing bifocals, and would have had to wake up in the middle of the night and look across a blurry area, through a passing train, to see the murder occur. All the jurors, save Three, vote “not guilty.” Three insists he won’t change is mind, and Nine points out that “it takes a great deal of courage to stand alone.” All jurors leave, except Three and Eight. Three picks up the switch knife from the table and points it at Eight. Eight says, “not guilty.” Three turns the knife and presents the handle to Eight. “Not guilty,” he says.
