What evidence indicates that Tom Robinson is guilty or innocent in Harper Lee's To Kill a Mockingbird?

As
the other answer has observed, the overwhelming majority of the evidence proves that Tom Robison
is innocent of the rape and beating of Mayella. Literally no circumstantial evidence pointing to
the possibility of Tom's guilt exists. In fact, much suggests that Bob Ewell is the one beating
and even sexually abusing Mayella.

The only thing that makes Tom guilty in
the eyes of the court is his race. They assume black men are all no good, little better than
animals. It was a common fear among white southerners that black men sought to prey upon white
women, so the very accusation of a black man hitting on a white woman, let alone sexually
assaulting her, could put a black man in danger of being lynched or imprisoned. All the evidence
in the world could not penetrate this prejudice.