Oddly, it is Scout who is more discerning of the truth when the jury deliberates for many hours. As Scout struggles to stay awake, an "impression" creeps into her. She says,
"The feeling grew until the atmosphere in the courtroom was exactly the same as a cold February morning, when the mockingbirds were still, and the carpenters had stopped hammering on Miss Maudie's new house, and every wood door in the neighborhood was shut as tight as the doors of the Radley Place."
Scout gets a feeling of ominousness, sensing that something bad is happening. Her suspicions are confirmed when the jury comes back in, and not one of its members looks directly at Tom Robinson. As "a lawyer's child," Scout knows that "a jury never looks at a defendant it has convicted." Despite the evidence, the jurors have found Tom Robinson guilty.
Jem, on the other hand, has been ecstatic since the lawyers finished their closing arguments. In his mind, the evidence is so clear, that he cannot fathom how Tom Robinson can be found anything but innocent. He at first thinks the jury deliberations should be over in just a few minutes, because as far as he is concerned, there is nothing to debate, but even when the deliberations drag on for hours, his optimism is not tempered. When Scout asks him, "Ain't it a long time?", he answers "happily...'Sure is, Scout.'" When she points out that he had intimated that it should "just take five minutes," he responds with unshakable faith in a positive outcome, "there are things you don't understand" (Chapter 21).