In chapter 30, Scout makes the connection between killing a mockingbird and dragging Boo through a trial for killing Mr. Ewell. She is able to feel compassion for him. She is able to see him as a human being rather than just some perverse neighborhood legend. Then in chapter 31, as she walks Boo home, she pauses at his window. She imagines for a moment what Boo must have seen out that window over the years. He must have been as fascinated by them as they were by him. It is in this moment that she fulfills what Atticus has always told her to do - try to see the worlds as others do.
In chapter 30, Scout asks Atticus: "It's sorta be like shootin' a mockingbird, wouldn't it?" She is referring to the possibility that Boo would be arrested for Mr. Ewell's death. Scout understands that Boo was trying to protect her, and realizes that if people knew and Boo was put on trial, it would be traumatic for this man who has spent his life as a hermit.
In chapter 31, Scout walks Boo home. On his front porch, she turns and she imagines the street and the community as Boo sees it. She understands that Boo loves his community and wants to protect it, and she finally "walks a minute in his shoes", as Atticus always urged her to do.
Well scout kows boo was trying to protect jem and herself so it would be wrong to put boo through trial for killing bob ewell