In To Kill A Mockingbird, the reader learns a pertinent fact about Tom Robinson's physical condition. Tom Robinson had a crippled left arm. When Tom was a boy, his left arm had become crippled by a cotton gin. There is no way that he could have assaulted Mayella with his left arm. According to Mayella's brusies, which were on the right side of her face, she was attacked or beat by someone with a strong left arm. Tom Robinson could not have been her attacker. The fact that his left arm was crippled proves that Tom Robinson could not have beaten Mayella.
Also, there were bruises around Mayella's neck. This indicates that someone with two good arms and hands tried to choke her. Again, Tom Robinson could not have brusied Mayella's neck. Also, when the reader considers that Tom Robinson was crippled in his left arm, this fact would provide evidence that he could not have raped Mayella. Mayella would have been able to free herself from Tom Robinson because he did not have two strong arms.