Atticus uses a simile when he says, "This case is as simple as black and white"—he makes a comparison between two unlike things using the word as. This statement is also ironic, because Atticus uses the common expression "simple as black and white," which means that the case is not a difficult one to understand since there are no complicated facts. But in the reality of Maycomb's society, there is an issue that complicates the case, because Atticus's statement also implies that the verdict comes down to racial issues, as a black citizen has been accused, and a white citizen has brought charges.

There is no ambiguity in the legal case. Atticus has proven that Tom could not have caused the bruises on Mayella, because they were made by a man's left hand, and Tom's left hand is withered and useless. On the other hand, this case is not truly as "simple as black and white." The irony is that the case is complicated by being about a black man and a white woman, for a black man is accused of raping and beating a white woman in the Jim Crow South. And, at that time the word of a white person is taken over the word of a black person. In this respect, the irony of Atticus's statement is that the case being "as simple as black and white" means that it really is not so simple for the jury. For Atticus asks a jury of twelve white men to set a precedent and vote according to their conscience and reason, not their culture.