A combination of evidence, statements, and unanswered questions point to the truth of what occurred regarding Mayella Ewell's charge of rape against Tom Robinson.
When Sheriff Tate is on the witness stand, he is asked to describe Mayella's injuries. Mr. Tate says that Mayella "was pretty bruised up" when he arrived, and "she had a black eye comin'." When asked which eye was injured, the sheriff corrects his first response and says, "It was her right eye, Mr. Finch. I remember now, she was bunged up on that side of her face...." After the sheriff makes this statement, it occurs to Atticus to look at Tom Robinson, because he knows that Tom has a useless left arm. He also knows that for Mayella to have an injured right eye, someone would have had to hit her with his left fist. Then, Atticus asks the sheriff a second time which side of Mayella was injured, and again the sheriff states that it was her right side. After this statement, Mr. Tate describes Mayella's other injuries. She was bruised on her arms, and her neck had finger marks on it. When Atticus asks which part of her neck was marked, Sheriff Tate testifies that the marks "were all around." This fact that the marks were "all around" Mayella's neck suggests that two hands were used to choke her neck, a fact that also points to the attacker's possessing two good arms and hands, unlike Tom Robinson.
Atticus makes a note of these facts but waits until he has questioned Bob Ewell and his daughter Mayella. While Bob Ewell is on the witness stand, Atticus asks Ewell to write his name. After he does so, Ewell wonders why Judge Taylor, Mr. Gilmer, and members of the jury watch him intently. "What's so interestin'?" he asks. "You're left-handed, Mr. Ewell," says Judge Taylor. With the establishment of Bob Ewell's being left-handed and Tom Robinson's left arm and hand having been rendered useless years ago, the bruises upon Mayella's right side of her face and all around her neck were probably inflicted by her father after he witnessed her advances toward Tom.
Further, when Mayella is on the witness stand, she claims that Tom Robinson sexually assaulted her, but when she also claims that she was screaming as he did so, Atticus asks her, "Then why didn't the other children hear you? Where were they? At the dump?" To this interrogation, Mayella makes no reply, even when Atticus continues to ask why her screams were not heard by any of the other children. Then, Atticus asks pointedly, "Or didn't you scream until you saw your father in the window? You didn't think to scream until then, did you?" Mayella does not answer these questions, either. Her silence incriminates her, because if what Atticus had asked was false, she would have made denials.