What misunderstanding do Atticus and Heck Tate have? What decision does Heck Tate finally make and why? ch 30

Atticus thinks that Jem must have done it since Scout named Jem as her protector in her story. However, the sheriff insists continually that Mr. Ewell fell onto his knife and killed himself, which irritates Atticus, who wants Jem to be treated as fairly as anyone else and not have exceptions made. After much arguing, finally the sheriff yells out that he's not trying to protect Jem (he is trying to protect Boo). The sheriff urges Atticus, this once, to accept the situation even if it's not perfect according to law: Mr. Ewell was responsible for Tom's death, and the sheriff urges Atticus to "let the dead bury the dead." He says that it would be a sin to drag shy Boo Radley out into the limelight, and declares officially that Mr. Ewell fell on his own knife.