In To Kill A Mockingbird, Tom Robinson is a black man who is on trial for rape. Mayella Ewell has accused Tom of raping her. She is pressured by her father to do so.
One day when Tom was walking by Mayella's house, she asked him for help. He helped her break up a chifferobe or dresser drawer:
Tom Robinson is a mild-mannered, conscientious black man whose kind acts earn him only trouble when Mayella Ewell accuses him of rape. Because he saw she was left alone to maintain the household without any help from her family, he often performed small chores for her.
Mayella made advances toward Tom and her father caught her.
Mayella was beaten by her father for her promiscuous behavior. Then her father tells Mayella to claim that Tom beat and raped her.
Atticus is appointed as Tom's lawyer. The judge realizes that Atticus will do a good job in representing Tom. Atticus is open minded. He is not prejudiced as much of Maycomb is. The judge realizes that Tom needs someone who will be fair and open minded. The judge is making sure Tom gets fair representation and Atticus is the best man for the job:
Atticus is a lawyer and also a member of the state legislature, elected by townspeople who respect his honesty even if they don't always approve of his actions.
No doubt, Atticus is highly respected. He will do his best to make sure Tom Robinson gets a fair trial. He realizes Tom is not guilty. Atticus proves that a left handed man beat Mayella. Tom's left arm is crippled. He could not have beaten Mayella. Bob Ewell, Mayella's father, is left handed. Atticus does a great job in proving Tom's innocence. However, in a town like Maycomb, Atticus' efforts can not save Tom. Because he is black, Tom is found guilty of a crime he didn't do.
Atticus is appointed by the court to defend Tom Robinson, a black man who has been accused of raping a young white woman, Mayella Ewell. Although many of Maycomb's citizens disapprove, Atticus agrees to defend Tom to the best of his ability.
Atticus is defending Tom Robinson because it's the right thing to do and he knows he's telling the truth, Atticus is not prejudicial like others in his town.
The judge appoints Atticus because he's the only one who'd be willing to take his case and failure, to the judge, is inevitable.