For the most part, the adults of Maycomb do not talk with Jem and Scout about the upcoming trial. Instead, the children gain bits and pieces of information from conversations they overhear. Scout tries to grill Reverend Sykes about Tom and his wife, Helen, but Calpurnia cuts off Scout's questions. Scout then asks Cal about Tom's troubles, but she tells Scout that "It's something you'll have to ask Mr. Finch about." The children hear plenty of gossip on the streets of Maycomb, however--both about the Finch family and the rape accusation against Tom.
"They c'n go loose and rape up the countryside for all of 'em who run this county care," was one obscure observation... (Chapter 14)
On their way to the courtroom, the children hear that Atticus has been appointed to defend Tom--their first inclination that Atticus has not voluntarily taken the case.
"... you know the court appointed him to defend this nigger."
"Yeah, but Atticus aims to defend him. That's what I don't like about it." (Chapter 16)
And they witness firsthand the lynch mob trying to take Tom from the jail, though neither Jem nor Scout seem to grasp the seriousness of the situation. Scout hears about the trial from several of her friends, particularly Cousin Francis and Cecil Jacobs, who taunt Scout about Atticus being a "nigger-lover."