Theodore Boone by John Grisham

Theodore Boone is thirteen and wants nothing more than to swap homeroom for the courtroom; he lives for big trials. Now the biggest murder case in his city's history is set to begin.
 
In the packed court, a husband awaits trial for his wife's murder. Is he a dangerous criminal or an innocent victim?
 
The case takes a sinister twist when Theo uncovers a surprise witness with his own problems to hide. But Theodore is sworn to secrecy and time is running out. Can Theo find a way to bring the killer to justice...or will a guilty man get away with murder?