To Kill a Mockingbird questions....?

3.) The sheriff knew that it was either Boo Radley or Jem who had killed Bob Ewell. Jem was only a child and didn't need a criminal record at such a young age (I think he was thirteen?). Boo Radley had lived all of his life away from the public, and to credit him with the death of Bob Ewell would have been to throw a spotlight on him that he didn't want, need, or deserve. Some would have been angry with him, others would have praised him, and everyone would talk about him even more than they did when he was a phantom. The sheriff is respecting both Boo's way of life and Jem's childhood when he tells Atticus that "Bob Ewell fell on his knife"