Sheriff Heck Tate's evidence contradicts later testimony given by the Ewells.
When the solicitor Mr. Gilmer questions Sheriff Tate, he asks basic questions about what has happened. Sheriff Tate testifies that as he was leaving his office, he was accosted by an "excited" Bob Ewell who wanted him to hurry to his house because "some n****r'd raped his girl." When he arrived, the sheriff testifies, he found Mayella "pretty well beat up," and he lifted her to her feet. After Mayella washed her face, the sheriff asked her who had hurt her, and she told him that it was Tom Robinson. She also told Sheriff Tate that Robinson "took advantage" of her. Mr. Gilmer says a mere "thank you," and he sits down.
As Atticus begins his cross-examination, he asks the sheriff if he called a doctor. Mr. Tate says, "No sir," and Atticus asks, "Why not?" Atticus repeats his question twice for effect. Then, Atticus asks for specific details about Mayella's injuries. Sheriff Tate describes the bruises that were on Mayella; he adds that the girl had a black eye.
"Wait a minute, Sheriff,"said Atticus. "Was it her left facing you or her left looking the same way you were?"
Mr. Tate said, "Oh yes, that'd make it her right. It was her right eye, Mr. Finch. I remember now, she was bunged up on that side of her face...."
At this point, Sheriff Tate realizes why Atticus asks him about which side of Mayella's face is blackened. He turns to look at Tom Robinson, who raises his head.
"Sheriff, please repeat what you said."
"It was her right eye, I said."
Atticus corrects him, saying "No." He walks over to the court stenographer and has Tate's exact words repeated: "Mr. Finch, I remember now she was bunged up on that side of her face." Atticus then asks Tate to specify again which side of Mayella's face that was. So, the sheriff reiterates, "The right side, Mr. Finch." The sheriff also adds that Mayella's throat and arms were severely bruised, as well.
By questioning Sheriff Tate in such a detailed manner, Atticus illustrates the impossibility of Tom Robinson's having been able to inflict the injuries on Mayella Ewell. That Mayella's right eye is blackened suggests that her attacker was left-handed, and Tom's left arm and hand are completely useless. Also, the throat bruises on each side of Mayella's neck appear to have been made by someone who had the use of both hands.