Juror #8 is a dude who cares about justice and is willing to stand up against a crowd to do what he thinks is right. In the beginning, we're not really sure what his deal is, because he starts kind of softly, saying, "There were eleven votes for guilty. It's not so easy for me to raise my hand and send a boy off to die without talking about it first." So at this early point, it sounds like he just wants to talk for a while before they reach a guilty verdict.
And, in fact, it doesn't take long before the other jurors start pressing #8 to give a Guilty verdict. They assure him that he'll never change their minds about the guilt of the defendant, but he responds by saying, "I don't want to change your mind. I just want to talk for a while. Look, this boy's been kicked around all his life. You know, living in a slum, his mother dead since he was nine. That's not a very good head start. He's a tough, angry kid. You know why slum kids get that way?"
In other words, this guy thinks that the defendant deserves a little sympathy and discussion before the twelve jurors send him off to die. But we sort of already know that he's just biding his time and angling to change some of the jurors' minds.
Not Just Moral, But Smart Too
Let's be real: Juror #8 is probably also the smartest guy in the jury room. When Juror #2 mentions that no one could prove the defendant didn't commit murder, #8 is quick to answer, "Nobody has to prove otherwise. The burden of proof is on the prosecution. The defendant doesn't have to open his mouth. That's in the Constitution. The Fifth Amendment. You've heard of it."
And when Juror #10 says that the jurors shouldn't believe the defendant because he's not white, #8 asks, "How come you believed [the non-white witness]? She's one of 'them,' too, isn't she?"
Despite all of Juror #8's tricky arguments, he never really gets any traction for a Not Guilty verdict until he shows the other men some solid evidence. This sets us up for one of the most dramatic moments in the movie, when #8 pulls a knife exactly like the murder weapon out of his pocket and jams it into the table, saying, "I got it last night in a little junk shop around the corner from the boy's house. It cost two dollars."
On top of everything else we know about him, we know that #8 has a little flair for the dramatic.
So, all right, Juror #8 is dramatic, just, kind, and smart. But none of these things would get him anywhere with the other jurors if he weren't willing to put himself out there and take risks. He takes his biggest risk of all early in the movie when he says, "I want to call for a vote. I want you eleven men to vote by secret ballot. I'll abstain. If there are still eleven votes for guilty, I won't stand alone. We'll take in a guilty verdict right now."
If this vote once again went for a unanimous Guilty verdict, this movie would be over, and there'd be nothing else to talk about. But Juror #8's trust in his fellow man pays off, as Juror #9 gives a Not Guilty verdict and puts us all on the path to setting the defendant free.
Go For the Death Blow
Once Juror #8 has managed to sway a few of the jurors, it's time for him to go on the offensive and attack the jurors whose prejudices prevent them from changing their minds. In one case, he basically calls out Juror #3 for wanting to murder the defendant in cold blood by giving a Guilty verdict. He doesn't mince words: "You want to see this boy die because you personally want it—not because of the facts."
This tactic works because #8 eventually makes #3 so flustered that #3 tries to attack him; he even says he'll kill him. To all of this, #8 calmly answers, "You don't really mean you'll kill me, do you?"—which shows that we shouldn't always believe people when they exaggerate, sure, but it also shows that Juror #8 is able to stand up to pretty much anything if he thinks his principles are being violated.
By the end of the movie, Juror #8 has proven himself to be a true hero for standing by his principles and having the courage and skill to put them to work. He eventually gets the jury to find the defendant Not Guilty, and in the process, he avoids sending an innocent 18 year-old kid to jail. He also helps restore our faith in democracy and human decency, which is pretty darn good for a day's work.