Another few evidences of the courtroom drama occur from Scout's vantage point.
First, Scout, Jem and Dill are separated from their father and his business and joined with the black folk up in the balcony. The separation between black and white creates an added drama for us in the 21st century that Lee hadn't planned on. To see Atticus' kids with the black folk made quite a statement, especially when Mr. Underwood pointed it out.
Second, Scout sees something that she views as dramatically symbolic. She had never see her father strip. He always wore his clothes tight and completely. In this trial, it is so hot (both literally and figuratively) she sees her father losen his tie, take off his jacket, and unbutton his vest. These are great symbols of the exhaustive work he is going to in order to get Tom Robinson off.
Part of the drama that builds during the Tom Robinson trial comes from the superb characterizations that Lee draws of Mayella and Bob Ewell. Both had only been mentioned briefly prior to the trial, but Bob and Mayella become powerful characters once they are exposed on the witness stand. Atticus is able to bring out the dark sides of their natures, and Mayella's emotionally charged appearance is one of the highlights of the novel.
Atticus' own character is shown in yet another light: We get to see his lawyering and oratorical skills in action--dissecting the evidence and bringing out new possibilities that refute the accusations against Tom. Atticus' brilliant closing statement is another high mark of TKAM.