One of the great, subtle scenes in the novel is when Dill, once he realizes how unjust this trial is going to be for Tom Robinson, has to leave the courtroom because he feels physically ill. Through this character, a young child, Harper Lee can make the point that this is how all people should feel about what is happening to Robinson. It is clear that there is no way that he could have committed the crime against Mayella, and it is clear that this town is not ready to deliver a verdict that implies that the white person is lying and the black person is telling the truth. Lee's themes about prejudice are all ultimately portrayed through the children. In this case, it is Dill who learns the hard lesson about prejudice and injustice, but he doesn't just accept it as an unhappy circumstance of life. He is affected and seeks to understand what it all means. He won't live his life thinking injustice happens and that is all there is to it.