How does Harper Lee use the courtroom scene in To Kill a Mockingbird to develop character, setting and the themes of fear and prejudice?
Several of the pivotal characters in To Kill a Mockingbird receive their strongest development during the Tom Robinson trial. We learn more about Bob and Mayella Ewell during their testimony than anywhere else in the novel. The same is true for Tom Robinson, about whom little is known before the trial.
THE EWELLS. Although Atticus has described the Ewell family as "the disgrace of Maycomb for three generations," little is known about the specific characters until the trial. We find that Bob is short but well-built, compared to a bantom chicken. He is poorly educated, racist, and a man with questionable honesty. Mayella is a frightened, haggard young woman--also poorly educated, friendless and angry (particularly at Atticus). She is her father's daughter in many ways, though deserving of far more sympathy than Bob.
TOM ROBINSON. Several revelations about Tom come to light only after the trial begins. Before the trial, we only know that Tom is a black man accused of raping a white woman. Certain expectations could have been made about Tom with such little background knowledge. But during the trial, Tom's true nature is revealed: He is crippled, soft-spoken and a hard-working family man--a true opposite of his accuser, Bob Ewell.
This is a huge question that will require a more in-depth look at chapters 17-20.
To get you started however, I think everything you've asked for (character, setting and themes of fear and prejudice) can all be summed up in this:
Atticus is defending an innocent black man (Tom Robinson) in a rape trial. Atticus is an excellent lawyer who makes it very clear in the trial that not only is Tom innocent, but it is the victim's father who is guilty. The facts are undeniable - however, despite this, the jury still convicts Tom Robinson of guilt. In this way, Lee portrays Atticus as a noble and integritable character who stands up to the fear of things that are different and racial prejudice of this small southern town to do the right thing.