All throughout the trial, as Jem watches, listens, and pieces together the evidence (or lack thereof) that his father brings to the jury's attention, he has hope. Jem says things like "He's just gone over the evidence . . . and we're gonna win, Scout. I don't see how we can't" (202). Jem believes in his father, he understands the case, and he knows that the prosecution has not provided any substantial evidence to prove that Tom Robinson raped Mayella Ewell. Jem is only eleven or twelve at this point and if he can understand the facts and determine that Tom is innocent, then it should be sure that twelve intelligent adult men could come to the same conclusion—right? Unfortunately, Jem's heart and hope are shattered as the word "Guilty" rings through the courtroom after the jury's long deliberation. As Jem's hope in humanity crashes to the floor, so does his childhood innocence. It is at this point that Jem gains a major life experience. Scout describes it as follows:
"It was Jem's turn to cry. His face was streaked with angry tears as we made our way through the cheerful crowd. 'It ain't right,' he muttered, all the way to the corner of the square where we found Atticus waiting. . . . 'It ain't right, Atticus,' said Jem. 'No son, it's not right'" (212).
In the Warner Books edition of To Kill a Mockingbird, this passage is found on page 212 as noted above. However, it is also the opening paragraph of chapter 22 and may be more easily found that way in a different edition.
In Chapter 22 of "To Kill A Mockingbird," Scout narrates,
"It was Jem's turn to cry. His face was streaked with angry tears as we made our way through the cheerful crowd. "Itt anin't right," he muttered, all the way to the corner of the square where we found atticus was standing under the street light looking as though nothing had happened: his vest was glistened, he was his impassive self again. It ain't right, Atticus," said Jem. "No son, it's not right."
This is where Jem has lost his innocence. When Tom Robinson was convicted and sentenced to death, unfairly, Jem's eyes are opened and he is angry. In my edition this is on page 224.