There are several techniques that Harper Lee uses in this chapter in order to make her point - the importance of not bringing Boo Radley into the limelight. More specifically, Heck Tate persuades Atticus that it is important to protect Boo.
First, Heck Tate uses an emphatic question and repetition to force the question of what Atticus believes happened. Here is what the text says: “Mr. Finch, do you think Jem killed Bob Ewell? Do you think that?” Heck does this to make sure that Atticus does not believe that Jem is responsible.
Second, Heck masterfully leads the conversation initially without saying much. In other words, Heck implies as much as he says. Atticus picks up on this. Here is what Atticus says:
“Heck, you haven’t said it, but I know what you’re thinking. Thank you for it.
Heck uses his investigative skills to make his point stronger. He seeks to reconstruct the scene. He says:
“He’d flung Jem down, he stumbled over a root under that tree and—look, I can show you.”
Heck also uses a quote from the New Testament to bring in a religious tone. He quotes Jesus' words, "let the dead bury the dead." He says:
There’s a black boy dead for no reason, and the man responsible for it’s dead. Let the dead bury the dead this time, Mr. Finch. Let the dead bury the dead.”