JUROR #8: The old man—"I'm gonna kill you," body hitting the floor a second later—would have had to hear the boy's words with the el [train] roaring past his nose!
This is the point where Juror #8 first brings up the possibility that the elderly witness in the murder trial might be making up parts of his testimony. For example, how could the old man hear the kid yelling upstairs with a massive train passing right outside his open window?
JUROR #6: A guy who talks like that to an old man really oughta get stepped on.
Juror #6 doesn't have much time for anyone who speaks disrespectfully to the elderly. Thank goodness someone feels this way, because Juror #3 definitely needs someone to knock some sense into him if he's going to keep yelling at poor old Juror #9.
JUROR #6: You oughta have more respect, mister. You say stuff like that to him again… I'm gonna lay you out.
In case Juror #3 didn't get his point the first time, Juror #6 tells him that he's going to slug him if he says another disrespectful thing to Juror #9. This is 1957, after all, and many of the people during this time wouldn't be willing to stand idly by and watch their elders get bullied by some pushy jerk.
JUROR #6: You go ahead. You say anything you like. Why do you think the old man might lie?
After taking Juror #3 down a peg, #6 turns back to the elderly #9 and invites him to give his opinion on why the elderly witness in the murder trial might be lying. This is one of the nicer moments in the movie; it reminds us that some people are still decent enough to give respect to old people who've worked hard their whole lives and now need respect for their age and wisdom.
JUROR #9: I mean, to come to court like that. He was a very old man in a torn jacket.
It might sound like Juror #9 is being cruel to the elderly witness who testified against the defendant. But he's actually giving the witness quite a bit of sympathy, saying that it must not be easy to show up at court in ragged clothes.
JUROR #9: And he walked very slowly to the stand. He was dragging his left leg and trying to hide it because he was ashamed.
It's important to note here that the old man dragged one leg while walking to the witness stand. After all, he testified that he ran to his door and saw the defendant running away from his building. But as Juror #8 points out, there's no way the man could cover this distance with a disability like that.
JUROR #9: I think I know this man better than anyone else here.
As he points out, Juror #9 understands the elderly witness better than anyone else because he knows what it's like to be an old man nobody (not even some of the other jurors) listens to.
JUROR #9: This is a quiet, frightened, insignificant old man who… who has been nothing all his life.
As #9 tells us, the poor old man who testified against the defendant might have made up some of his testimony because he just wanted a little attention. It can't be easy to sit alone in your apartment all day just watching the days go by and waiting to die.
JUROR #9: Nobody knows him. Nobody quotes him.
It's clear by this point that the old witness in the murder case has a reason to get up in court and lie about his testimony. He saw the opportunity to be important for one last time in his life and he didn't hesitate to take it.
JUROR #9: Nobody seeks his advice after 75 years. Gentlemen, that's a very sad thing—to mean nothing.
In conclusion, we learn from Juror #9 that it's very sad to be an old man with no family; no one cares about who you are or what you have to say. So is it any wonder that this old man would step up and try to be important for a few minutes by making up some court testimony? After all, what are they going to do to him if they catch him lying—put him in jail for the rest of his life?