When Scout's Uncle Jack joins the family for Christmas in Chapter 9, Atticus reveals to his brother the truth about how he came to defend Tom Robinson. Atticus did not seek out the case; instead, it was thrust upon him by Judge John Taylor, who knew that Tom would get better representation from Atticus than from a public defender. Atticus knows that defending a black man accused of raping a white woman will make enemies in the town and bring trouble to his family, but he feels that he has little choice in the matter.
"... do you think I could face my children otherwise? You know what's going to happen as well as I do, Jack, and I hope and pray I can get Jem and Scout through it without bitterness... I just hope Jem and Scout come to me for their answers instead of listening to the town. I hope they trust me enough..."