What are two examples of logos in To Kill a Mockingbird during Atticus's case?

Coined by Aristotle and used with the art of rhetoric, logos means logic, or the use of factual evidence during a debate or argument. The Tom Robinson case is not based in logical findings; rather, it is based on hearsay without additional witnesses. Thus, Atticus must use as much logic available to build a proper defense for Tom. Most of his arguments use logic based on the prosecution's lack of evidence that is missing, unavailable, or nonexistent. What's missing? Third party witnesses to the crime. What's unavailable? Medical evidence that Mayella was in fact raped. What's nonexistent? Tom's left arm!

First of all, the only person close to being a third party witness to the events of the case is Heck Tate, the sheriff. He happened upon the scene after the fact and was able to see that Mayella was beaten up mostly on the right side of her body. This suggests that the perpetrator is left-handed. Atticus uses logos, or undeniable facts, to prove that Mr. Bob Ewell is left-handed by having him write his name on a piece of paper in front of the court. Scout summarizes as follows:

"Atticus was trying to show, it seemed to me, that Mr. Ewell could have beaten up Mayella. . . If her right eyes was blacked and she was beaten mostly on the right side of the face, it would tend to show that a left-handed person did it" (178).

Next, medical evidence was unavailable and non-existent to prove that the crime had happened as the Ewells were claiming. When Atticus asks the sheriff why he didn't call a doctor for Mayella, he says that he didn't need to because "She was mighty banged up. Something sho' happened, that was obvious" (167). If there had been a doctor called, Atticus would have been able to ask a medical expert if Mayella had actually been raped, or only beat up. Since there was no evidence to draw from, Atticus couldn't show more logos here other than the lack thereof because both the sheriff and Mayella's father didn't handle the situation right.

Finally, Atticus draws a logical conclusion between Bob Ewell's left-handed dominance with Tom's disabled left arm. Once Atticus establishes that Bob could have beaten his daughter and Tom could not, a logical syllogism is created and supported. A syllogism is a logical process of thinking based on an established premise. For example, if Mayella was beaten on her right side, then a left-handed person did it. Bob is left-handed. Tom not only is right-handed, but his left arm and hand have been disabled since he was younger due to a cotton gin accident. Unfortunately, the use of logos wasn't enough to conquer the social traditions of Maycomb county to let Tom Robinson go free.