In Chapter Five of Harper Lee's To Kill a Mockingbird, Atticus gets Jem to admit to what he and the other kids have been doing (playing games about the Radleys), by using a "lawyer's trick."
The children have been playing "The Radley game," where they make up stories about Boo and his family, using gossip they have heard, and their imaginations to fill in the gaps. They have even snuck scissors out of the house behind Calpurnia's back to recreate the scissor-stabbing attack that Boo allegedly turned on his father.
When Atticus comes home, the kids are so wrapped up in what they are doing, that they don't even realize his is watching them, but when they see him, they know he is not pleased. Atticus asks them what they are doing and Jem answers, "Nothin'." Atticus presses on and Jem admits that they were trying to pass a note to Boo, to ask him to come out, thinking he might enjoy their company.
In clear terms, Atticus tells the children to leave Boo alone; he has a right to privacy just like everyone else. Further, they are not to play an "asinine game he had seen us playing" or make fun of Boo. Before this, the kids had been suspected of playing a game about the Radleys, but Jem had denied it. Now he says they were not trying to make fun of Boo or laugh at him, admitting to Atticus that they had been playing the game before when Jem had denied it. This is the lawyer's trick Atticus uses because when Jem insists they weren't making fun of Boo, he does admit that they were reenacting everything they knew or didn't know about Boo's private life, out in the open, on the street.
Atticus grinned dryly. 'You just told me,' he said. 'You stop this nonsense right now, every one of you.'
Jem just stares at his father, bewildered at how he had been tricked. It is at this point that he decides that maybe he doesn't really want to be a lawyer when he grows up.