In Twelve Angry Men, for what reasons do all but one of the jurors believe the young man is guilty?
They mainly believe that the young man is guilty for circumstantial and stereotypical reasons. The young man had a history of fighting. That night, the suspect had a big fight with his father where, when he left, he was heard shouting that he'd kill him. The lady across the train said she saw him do it, and the neighbor down the hall said he saw him running away after the murder. He had recently bought a knife that looked like the one used to kill his father, and he no longer could produce it. The suspect had no verifiable proof that he was at the movie theaters, as claimed. Essentially, he was a victim of bad-timing -- he was a troubled kid, with a troubled past, and couldn't prove that he didn't commit the crime, so most assumed that he did.