In To Kill a Mockingbird, what is peculiar about Tom which would lead one to believe he could not have grabbed, beaten, or raped Mayella Ewell?

In Chapter 18, Atticus asks Mayella Ewell to identify the man who allegedly beat and raped her. Mayella indicates that Tom Robinson was the man responsible, and Atticus asks Tom to stand up.When Tom stands up, that entire community and jury can see that Tom has a crippled left arm. Scout says that it is twelve inches shorter than his right arm and hangs dead at his side. She mentions that Tom's hand was...

In Chapter 18, Atticus asks Mayella Ewell to identify the man who allegedly beat and raped her. Mayella indicates that Tom Robinson was the man responsible, and Atticus asks Tom to stand up. When Tom stands up, that entire community and jury can see that Tom has a crippled left arm. Scout says that it is twelve inches shorter than his right arm and hangs dead at his side. She mentions that Tom's hand was small and shriveled. Scout can see that his left arm and hand are of no use to him. Reverand Sykes tells Scout that Tom had his arm caught in Dolphus Raymond's cotton gin as a boy and almost bled to death. He says that Tom's muscles were torn loose from the bone, and his injuries were severe. Tom could not have possibly strangled Mayella around her neck with his crippled left arm, let alone hold her down while he raped her. Mayella's injuries to the right side of her face indicate that a man who lead almost exclusively with his left hand beat her in the face. There is sufficient evidence that suggests her left-handed father, Bob Ewell, was responsible for Mayella's injuries.