How justice is one of the themes in Mockingbird?

Justice is a major theme in the novel, one that Scout and Jem learn about and come to understand because of their father's work.... work that he refuses to back down from. Over the course of the novel, Jem and Scout are exposed to true "injustice", as they see Tom Robinson convicted of a crime he didn't commit purely because he is a black man and his accuser is white. There is no justice in a world where the evidence is so powerfully in favor of the defendant, that race is clearly the single defining factor in the jury's verdict. Atticus fights against racism and injustice, relentlessly pursuing justice for Tom, even though he is overwhelmingly unsupported by the people of Maycomb. When Atticus loses the trial, he tries to make his children understand that although he lost.... that even though justice hadn't been served, his work was not in vain. In representing and working for Tom, Atticus' actions did help move along the cause of ending racism as evidenced by the jury's lengthy deliberation period. Usually, such a trial would be decided immediately.