How does Scout's story about her family and community set up how we ultimately judge the actions of the key characters? How does this background set up the trial at the center of the book?

Harper Lee describes Maycomb, Alabama, in detail so that we may ultimately judge the actions of the main characters of the book. One example is Sheriff Heck Tate, who readers come to appreciate as a man who would rather not have to arrest Tom Robinson yet understands that a Southern sheriff in the 1930s cannot disbelieve an accusation by a white (of any status) against any African American and must do his job. Another is Judge John Taylor, who also knows he is presiding over what is in essence a sham trial and who does everything in his power to demonstrate as such. Yet, like the sheriff, Judge Taylor knows that the boundaries of what he can do in 1930s Alabama stretch only so far. Bob and Mayella Ewell play their parts as well—Mayella may lust after Tom, but it is impermissible for her to act upon her desires, so when she does, Tom must be to blame, while her father cannot accept that Mayella could break Southern mores and so must accuse Tom to save the family honor. Finally, there is Atticus himself, railing against the injustice of Tom's arrest and trial, showing everyone that the Ewells are lying and that the only reason Tom is on trial is that he is black in the 1930s South. Readers feel sorry for Atticus at the end, when Tom is inevitably convicted of rape and sentenced to death, because we hoped he'd somehow succeed against the odds, and we know the verdict eats at his soul. In the end, when Bob tries to exact his revenge on Atticus, it's the only conclusion we could expect. Bob represents the last vestiges of the Old South, trying to keep blacks in their place and whites predominant in the world and looking to harm Atticus's family, who represent the New South, which can't and won't be denied.