When Tom Robinson is arrested, accused of raping Mayella Ewell, Judge Taylor specifically asks Atticus to represent Tom, instead of passing the case along to the inexperienced public defender, as normal court procedure would dictate. This speaks well of Judge Taylor; he knows that Atticus, because of his character and experience, will give Tom the best defense possible in court. Atticus cannot refuse, even though he understands the difficult job he has been given and can foresee how Tom's case will affect the primarily racist Maycomb community. He also understands that his taking Tom's case will affect his children's lives, although he cannot possibly foresee that Mayella's father will one day attempt to kill them. Such human depravity is beyond his imagination. Atticus defends Tom with all his strength and ability because he feels a moral responsibility to do so.
The majority of the white citizens of Maycomb accept that Tom has a defense attorney, although they can't understand why Atticus would take on his case. We can infer that black defendants do not generally receive a vigorous defense in court, based upon the town's reaction to Atticus' subsequent efforts on Tom's behalf. When Atticus presents a strong case for the defense and destroys Mayella's and her father's testimony at trial, the mood in Maycomb turns even uglier. Atticus, however, continues to do his best for Tom Robinson. After Tom is convicted, Atticus immediately makes plans to appeal his conviction, something he is not obligated by law to do. Atticus, however, is obligated by conscience and his belief in Tom's innocence.