What passages in To Kill a Mockingbird show Scout's loss of innocence?

To lose one's innocence is to understand that the world is not really the good, wonderful place one has always imagined it to be. One who has lost one's innocence instead realizes that there is evil in the world as well as good. Loss of innocence is a central theme throughout Harper Lee's To Kill a Mockingbird, and Scout loses her own innocence in multiple ways.

Scout loses her innocence the more she learns about Tom Robinson's case. One thing she knows early in the story is that Robinson is on trial for rape, yet Scout doesn't know what rape is. When asked, Atticus gives her a mild definition: "[R]ape was carnal knowledge of a female by force and without consent" (Ch. 14). However, she learns more about rape as she observes the trial and through conversations after the trial. During Bob Ewell's testimony in Robinson's trial, Judge Taylor denies a request to clear the courtroom of women and children, and Scout refuses to leave upon Reverend Sykes's request. Jem also refuses to take her home, arguing that she doesn't understand what rape is because she's not yet nine. Even if Scout does not truly learn what rape is during the court case, she certainly learns a great deal about violence. Specifically, she learns that Mayella had been severely bruised and even strangled by some person; this knowledge is enough to help Scout begin to lose her sense of innocence.

As Scout and Jem sit with Reverend Sykes waiting for the jury to return and Jem continues to talk about the case, Scout continues to learn that rape is associated with violence. More specifically, when Reverend Sykes warns Jem not to be so sure the case has been one, Jem asserts they couldn't have possibly have lost the case since it wasn't truly even a rape case. He continues to state his own definition of rape:

[I]t wasn't rape if she let you, but she had to be eighteen--in Alabama, that is--and Mayella was nineteen. Apparently you had to kick and holler, you had to be overpowered and stomped on, preferably knocked stone cold. (Ch. 21)

This definition of rape alone is enough to show Scout that rape is associated with extreme violence, knowledge that helps lead to her loss of innocence.