What is the relationship between the trial of Tom Robinson and the Boo Radley subplot in the novel?

In To Kill a Mockingbird, both Tom Robinson and Boo Radley are misunderstood characters that are not guilty of the "crimes" they are accused of committing. In the case of Tom, he feels sorry for Mayella Ewell and stops to assist her with her work. She and her father accuse him of raping her. Her father has to create a way to explain the bruises he gives to her, and when he finds her with a black man, he sees the perfect opportunity. Tom can be considered a "mockingbird." Early in the novel in Chapter 10, Atticus says, "it's a sin to kill a mockingbird." Tom is found guilty because Maycomb County jurors side with a white man over a black man.
Boo Radley, also a "mockingbird," is another character that is unjustly punished primarily for being misunderstood. Boo is confined to stay inside his house first by his father, then by his brother. He is the topic of many neighborhood superstitions and tales. For example, Miss Stephanie Crawford believes he was outside her window once looking in on her. The children are scared of being too close to the Radley property but by the end of the story, they begin to recognize that Boo's intentions are kind. In Chapter 3, Atticus explains to Scout that "You never really understand a person until you consider things from his point of view." Scout matures throughout the novel and begins to consider her father's words, especially in the case of Boo.
Near the end of the novel, the two stories merge when Bob Ewell attempts to kill Scout and Jem. Bob is angry because Atticus makes it clear that he is the one that injures his own daughter. Boo Radley intervenes and kills Bob Ewell in the process. The sheriff and Atticus agree that it would be wrong to drag Boo into the spotlight, so they decide to stick with the story that Bob fell on his own knife. Scout agrees and says, "it'd be sort of like shootin' a mockingbird."