There is little doubt at any time during the novel that Atticus does not plan to defend Tom Robinson as fervently as possible. He tells his brother, Jack, that he "hoped to get through life without a case of this kind," but Judge Taylor's request made it virtually impossible for Atticus to turn it down. He also tells Jack that he plans to "jar the jury a bit" even though he knows there is no chance that a white jury will take the word of a black man over a white man. However, Atticus doesn't believe he can face his children if he doesn't defend Tom. "You know what's going to happen as well as I do," he continues.
The townspeople also know Atticus means business. "Yeah, but Atticus aims to defend him," one man tells another on the day of the trial. After the trial, Miss Maudie tells Jem that Atticus is "the only man in these parts who can keep a jury out so long in a case like this." Atticus knew a win was out of the question, but his true hope rested with a successful appeal. Tom's death prevented that possibility from happening.