Atticus tells Scout that the best way to understand someone is to spend some time inside his or her skin. This is good advice for a lawyer, because in order to get at the truth you have to look at things from others’ perspectives.
You never really understand a person until you consider things from his point of view-…"-until you climb into his skin and walk around in it." (ch 3)
Atticus does this during the trial, first with Bob Ewell and then with Mayella. Atticus understands the Ewells. He tries to explain their weird behavior to Scout.
Atticus said the Ewells had been the disgrace of Maycomb for three generations. None of them had done an honest day's work in his recollection. (ch 3)
Atticus tells Scout that the Ewells are people, but they “live like animals.” This understanding helps him to get Ewell to say what he wants him to say during his cross-examination. He asks him if he heard what the sheriff testified, but it was to trap him into basically confessing that he hit his daughter.
"Oh yeah," said the witness. "I hold with everything Tate said."
"You do?" asked Atticus mildly. "I just want to make sure." (ch 17)
Atticus knew that Ewell would be haughty, and that he was relatively uneducated. He would not be able to see what Atticus was building up to. Atticus used Ewell’s pride against him, and got him to confirm testimony that Mayella was beaten on the right side of her face. He then got Ewell to demonstrate that he was left-handed, basically proving it might have been him. All he needed to do then was show that Robinson did not have use of his left hand.
After the trial, Ewell realizes that Atticus made a fool of him and spits in his face and threatens to kill him. In a drunken rage, he attacks Jem and Scout and might have killed them if Boo Radley had not intervened.
Atticus has a harder time with Mayella, because she is so young and ignorant. He tries to be polite to her, but she thinks he is sassing her. He tries to get her to drop her guard by saying he is an old man with a bad memory, but she looks at him furiously.
Yet he also gets her to go into detail describing her life.
Slowly but surely I began to see the pattern of Atticus's questions: from questions …Atticus was quietly building up before the jury a picture of the Ewells' home life. (ch 18)
Although Atticus does not get Mayella’s cooperation, she answers his questions and tells everyone about her life. This way, Atticus can establish to the jury that she leads a sad, lonely, desperate and difficult life. Again, this supports Tom Robinson’s testimony that he felt sorry for Mayella and tried to help her.
Understanding people’s perspectives is a valuable tool for a lawyer. By putting himself in Bob and Mayella Ewell’s skin, he was able to determine what really happened on the fateful night Tom Robinson was accused, and show the jury he was innocent.