We get a shot of the front of a courthouse before the shot cuts inside to show a bunch of people milling around. A dude with glasses walks through the hallways and passes a group of people celebrating a court victory. Said dude enters a courtroom, where someone is being tried for first-degree murder.
The judge explains to the twelve male jurors their responsibilities in voting on the fate of a man accused of murder. Overall, the judge seems pretty bored with the whole process, as if he's seen so many people sent to Death Row that he doesn't even care anymore.
We get a look at a young non-white man, who looks worried about what the jurors are going to decide. Then the title of the movie and the opening credits flash up while the jurors enter the decision room.
Some of the men joke about the weather, while one of them cuts up paper in case they want to vote by written ballots. In one corner, one of the jurors says that if he were in charge, he'd slap down all the tough kids in America before they ever had a chance to make trouble. In his mind, kids go bad because they haven't had enough discipline.
The 12 men seem eager to get going with their decision as they take their seats. Some of them seem to think they'll decide pretty quickly, because it's obvious the kid is guilty.
The foreman (Juror #1) reminds the men that if they vote guilty, they'll be sending the boy to the electric chair.
The jurors take a preliminary vote and find that 11 are voting "Guilty" and only one is voting "Not Guilty." So, obviously, all eyes turn to that guy, Juror #8, who happens to be played by the great Henry Fonda.
The guys want the one naysayer to change his vote to guilty, but he doesn't want to send a boy to his death without talking about it first.
Juror #8 talks about what a miserable life the accused kid has had. Apparently, the kid's father was really abusive, and it sounds like the kid stabbed him when he'd finally had enough of the abuse. Juror #8 thinks that the men owe the kid a few words, but Juror #10 thinks they don't owe the kid a thing.
As Juror #10 keeps talking, it becomes clear that he's pretty racist and just assumes that non-whites can't be trusted in general. Juror #9 (the old man) tries to tell him he's ignorant, but he gets talked back into his seat by the other jurors.
Finally, the men decide to go around the table and have each juror explain his reasons for why he voted guilty. Juror #2 goes first and says he thought it was obvious, because no one could prove the kid didn't do it. But Juror #9 reminds him that the burden of proof is on the prosecution and not the defendant.
Juror #3 pipes up and says that the facts clearly point to the kid being guilty. He was seen fleeing the scene just before his dad was found with a knife in his chest by police. The kid also claimed he was at the movies all night but couldn't name which movies he'd gone to. Finally, a female witness claims that she saw the killing take place.
When Juror #10 starts going on about the woman's story, Juror #8 (Fonda) asks him why he believes the woman's story, since she's non-white, too, and the guy has already said he doesn't trust non-whites.
Juror #5 passes on giving his reasons for his guilty verdict. Juror #6 says that for him, the motive for the murder is the most important thing for him. He thinks that the testimony about the argument that the boy had with his father is compelling evidence. But Juror #8 thinks this means nothing.
Juror #6 says the kid has such a long track record of antisocial behavior that it's easy to believe he committed murder. But Juror #8 insists that this still isn't a strong enough reason for sending someone to the chair.