After the guilty verdict, the children learn that Bob Ewell wants to harm Atticus and has already spit in his face. When they ask him about it, all he does is make the dry and humorous comment:
"I wish Bob Ewell wouldn’t chew tobacco."
Jem, upset about everything that has happened, including the latest wrinkle with Bob Ewell's anger, bursts out that there shouldn't be jury trials, because the verdicts are unfair. Atticus replies that the main problem is that the laws need to change, but states that this is a long, slow process. As he discusses the legal system with the children, Scout becomes indignant when she learns that women are not allowed to serve on Alabama juries. To diffuse her outrage at the injustice of the system, Atticus cracks a joke:
“I guess it’s to protect our frail ladies from sordid cases like Tom’s. Besides,” Atticus grinned, “I doubt if we’d ever get a complete case tried—the ladies’d be interrupting to ask questions.”
Jem and Scout laugh at this, showing they know that Atticus doesn't mean what he says about women interrupting and is only poking fun at social stereotypes.
Atticus realizes the system is unjust, and he knows he is in danger, but he tries to lighten the situation with some jokes.