Atticus manages to squeeze some important information from the frightened Mayella during her emotional time on the witness stand. First, Atticus gets Mayella to admit that Bob is not always the perfect father. When Atticus asks if Bob is always good to her, she tells Atticus that
"He does tollable, 'cept when--"
"... Except when he's drinking?" asked Atticus so gently that Mayella nodded. (Chapter 18)
Although Mayella does not give Atticus an audible answer, it is clear that Bob is a different man when he is drinking. Bob has already testified that he saw Tom "ruttin' on my Mayella," and that her face was bruised, but when Atticus asks her if she could "remember him beating you about the face," Mayella responds,
"No, I don't recollect if he hit me. I mean yes I do, he hit me."
"Was your last sentence your answer?"
"Huh? Yes he hit--I just don't remember... it all happened so quick." (Chapter 18)
When Atticus later asks if it was Bob who had beaten her, Mayella does not deny it, choosing to remain silent. Perhaps the most incriminating evidence against Bob comes during Tom's testimony, when he claims that Bob threatened Mayella after catching her with Tom.
"... you goddam whore, I'll kill ya!" (Chapter 19)
As Chapter 18 of Harper Lee's novel To Kill a Mockingbird begins, Mayella Ewell, the grown daughter of the town's most virulently racist and repugnant individual, is called to the witness stand in the trial of Tom Robinson, the African American accused of raping Mayella. In the previous chapter, Bob Ewell, Mayella's father, testified that he heard his daughter screaming and saw Tom run away. From the opening chapters of To Kill a Mockingbird, Lee's young narrator, Scout, has noted that the Ewell family is distinguished by their abysmal hygiene and disdain for education. Bob, the father, is a drunk and a racist, and he is known for the manner in which he raises his children, with Mayella, the oldest, forced to bear the burden of providing what domestic stability exists while her father drinks away what little money they have. When, in Chapter 17, Bob Ewell testifies in the rape trial, he is disrespectful towards the court and, it is assumed and later validated, lying despite being under oath.
When Tom Robinson's defense attorney, Atticus Finch, is presented with the opportunity to cross-examine Mayella, he is able to draw out of the uneducated, ignorant young woman the fact of her father's abusive nature--key to undermining her claim to have been raped by Tom. Atticus knows that it was physically improbable if not impossible for his client to have raped the full-grown and physically formidable Mayella, as Tom, it will be revealed, has a crippled arm. Atticus also strongly suspects that it was Bob Ewell himself who beat and possibly raped his daughter. His task, then, is to draw out of Mayella the truth about her father, despite the fear she holds of Bob's retribution should she fail to stick to her highly improbable story. The first instance of this occurs with the following exchange:
“Do you love your father, Miss Mayella?” was his next question.
“Love him, whatcha mean?”
“I mean, is he good to you, is he easy to get along with?”
“He does tollable, ‘cept when –“
Mayella looked at her father and he sat up straight and waited for her to answer.
“Except when nothin’,” said Mayella. “I said he does tollable.”
Mayella is about to say that her father is abusive when he has been drinking, which is frequently the case, but catches herself, as she will again in the following passage when Atticus asks her straight-out if it was her father who beat her:
“Who beat you up? Tom Robinson or your father?”
While Mayella will continue to deny that her father was the culprit and continue to insist that Tom Robinson raped her, Atticus has made his case. That Tom will be convicted anyway, however, illuminates the extent of the racism permeating the atmosphere in which Lee's story takes place.