Atticus essentially tells the jury that they have a duty to do their job fairly. He reminds them of the facts that his case has uncovered. He lets them know that it is obvious that guilt is reigning in the courtroom, but on the behalf of the plaintiff, and for various reasons. Mayella wanted to put the pain of her social sin behind her. He reminds them that the state hasn't done anything to prove Tom guilty. He points out the truth of Tom's capacity and character to do this. He challenges the court on the issue of race. He cites the Declaration of Independence and demonstrates that the courts are the one place in a society where a man should receive justice. He calls them to do their duty and make sure to make the right call regarding this man's life.
Atticus's closing speech is found at the end of chapter 20 where he begins by saying that there aren't many complicated facts in this case. What the jury must remember, and what Atticus does not take time to retell for them is first, Mayella was beaten on her right side which signifies that the abuser was left-handed. Mr. Ewell is left-handed and Tom Robinson's left hand is crippled and unable to have hurt anyone. Next, there is no medical evidence showing that Mayella was raped by anyone, let alone by Tom. Finally, there are no secondary witnesses to testify for either side to say who is telling the truth. Therefore, Atticus shifts all of the blame to Mayella Ewell and places the word guilty upon her during his closing arguments. Atticus also blames the South's social and racial boundaries for the situation that the Ewells and Tom Robinson find themselves in that day.
Atticus begins his closing arguments by saying that the facts aren't difficult and that the "case is as simple as black and white" (203). He reminds the jury that the prosecution has no evidence but the testimonies of two white people against that of a black man. Atticus attacks Mayella's guilt by saying it is linked to the unwritten social rule that whites and blacks shouldn't mix. When she tried to kiss a black man, and got caught, she had to save her face the only way she knew how and that is to blame Tom for raping her. Atticus then retells the story of what really happened that night, in spite of the Ewell's testimonies stating otherwise. He then tells the court that there is a misconception that prevails in the South, which is that "all Negro men are not to be trusted around our women, an assumption one associates with minds of their caliber" (204). In an effort to bring the jury over to his side, Atticus reminds them that they all have lied, done something immoral, or looked on a woman with desire, so they shouldn't judge Tom so harshly. Then Atticus ends by claiming that the courts are where we should all find justice, not just whites.