There are several significant pieces of evidence that the jury purposely ignores during the Tom Robinson trial.
1. The jury completely ignores the fact that there is no medical evidence that proves Mayella Ewell was raped.
2. The prejudiced jury also ignores the fact that Mayella's injuries were located on the right side of her face as well as around her neck, which suggests that her father was her perpetrator. Given the fact that Tom Robinson has a crippled left arm that is completely useless and Bob Ewell is left-handed, one could surmise that Bob was his daughter's attacker.
3. The jury also ignores Mayella's conflicting testimony. During Atticus's cross-examination, Mayella switches her story several times and contradicts herself, which indicates that she is obviously lying.
4. The jury also neglects Mayella and Bob's motivation to lie about Tom Robinson assaulting and raping her. Atticus makes it clear that Mayella broke a time-honored code by tempting a black man, which prompted her father's violent response.
Atticus has seemingly presented enough evidence to contradict the statements made by the "eyewitness" to Mayella's rape--her father, Bob. First, no doctor was ever called to determine if there was actually a sexual assault. (Additionally, no rape kit was available in the 1930s to determine if Tom was Mayella's attacker.) According to Atticus, and with the agreement of Sheriff Tate, Mayella's bruises on her face could only have been caused by a left-handed man. When Atticus requests Bob to sign his name, he signs with his left hand. The bruises around Mayella's neck could only have been caused by a man with two good hands, and Tom's
... left arm was fully twelve inches shorter than his right, and hung dead at his side. It ended in a small shriveled hand. (Chapter 18)
Tom's crippled left arm precluded him from either punching or choking Mayella. The jury also chose to ignore all of Tom's testimony, which included Bob's threat to his daughter:
"... you goddamn whore, I'll kill ya." (Chapter 19)