What caused Bob Ewell's death?
Bob Ewell died from a knife wound. The cause of death given by Heck Tate was that Bob Ewell fell on his knife. At first, Atticus thought that Jem had stabbed Bob Ewell. Atticus was prepared for his son to go to trial. Then Mr. Tate informed him that it was Boo Radley who killed Bob Ewell. This was when Mr. Tate decided that they should simply conclude that Bob Ewell fell on his knife. This would protect Boo Radley from going to trial for murder.
This did not sit well with Atticus. He felt that it was dishonest. Scout, however, understood. She agreed with Mr. Tate's decision to not place the blame on Boo Radley. When she thought of Boo, she thought of innocence. She knew he was just trying to save her and Jem's lives. She did not think it was fair for Boo to go to jail for what happened:
"Well, it'd be sort of like shootin' a mockingbird, wouldn't it?" (To Kill a Mockingbird, Chapter 31).