This question has already been answered.
The exculpatory evidence in Tom's trial is indirect or circumstantial evidence.
Heck Tate testifies that the perpetrator used the left hand. Tom has an injured left arm. Bob Ewell writes with his left hand.
The accusatory evidence in Tom's trial is direct evidence. Mayella is a witness to her assault.
he does not prove it at all to the reader. The jury is however convinced of his guild because of their prejudice. The reader can be unbiased.