Chapter 19 ends when Scout takes Dill outside after getting sick while listening to Mr. Gilmer's cross examination of Tom Robinson. So, the tension has already been building inside the courthouse.
Dolphus Raymond helps Dill calm down with some Coca-Cola. Mr. Raymond pretends to be a drunk to give people a reason to hate him, a reason other than the fact that he is in an interracial relationship. Although Scout's and Dill's conversation with Mr. Raymond continues the theme of racism in Maycomb, this interlude actually interrupts the tension created by the trial in court.
The tension resumes when the kids go back into the courtroom to hear the closing arguments. This is the moment of rising suspense and tension because this signals the end of the trial. One of the most rousing points in Atticus' closing speech is near the end when he challenges the jury to be fair.
Gentlemen, a court is no better than each man of you sitting before me on this jury. A court is only as sound as its jury, and a jury is only as sound as the men who make it up. I am confident that you gentlemen will review without passion the evidence you have heard, come to a decision, and restore this defendant to his family. In the name of God, do your duty.
The chapter ends with Atticus' speech and Calpurnia approaching to tell Atticus the children are missing. But the suspense increases with the rising action of the closing arguments of the trial. The trial is one of the, if not the most, significant event in To Kill a Mockingbird. The tension is also augmented by the fact that the jury is challenged to put aside any thoughts of racism. In a sense, the courtroom is a crucible, a testing ground. In that same sense, the jury is also on trial; they are being challenged to think objectively, to go against the social traditions and residual racism of Maycomb.