What point did Atticus try to get across to the jury during his closing statement in the trial?

Atticus explains that the case is very simple, because there is no medical evidence and very questionable testimony to prove Tom's guilt. Atticus explains that Mayella has, "broken a rigid and time-honored code of our society" by attempting to seduce a black man. He acknowledges her poverty and ignorance, but says, "I cannot pity her: she is white." He explains that Mayella followed her desires even though she was aware of the social taboos against her actions. Having broken one of society's strictest codes, she chose to, "put the evidence of her offense," namely Tom Robinson, away from her by testifying against him. Atticus accuses Mayella of trying to rid herself of the source of her own guilt.

Atticus suggests that Mr. Ewell beat his own daughter, as shown by Mayella's bruising on her right side. Mr. Ewell leads predominately with his left, while Tom can't punch with his left hand at all. Atticus points out that the case comes down to the word of a black man against the word of the white people, and that the Ewells' case depends upon the jury's assumption that "all black men lie." Uncharacteristically, Atticus loosens his tie and removes his jacket, which Scout and Jem are astounded to see, because he never walks about so casually. In his final remarks, Atticus speaks directly to the jury, earnestly reminding them that there are honest and dishonest black people just as there are honest and dishonest white people. He tells the jury that in a court of law, "all men are created equal." A court is, however, no better than the members of its jury, and he urges the jury to do their duty.