Forewarned is forearmed. Call it payback. The film is deceptive on other scores, as well. Major Hays, who turns out to be more than just a retired combat veteran, but an attorney, expresses to his own family how inadequate he feels about defending anyone, let alone one of his best buddies and the man who had once saved his life. Then, it turns out that he's a fierce defense lawyer who never misses a cue to object to a bad prosecutorial question and knows every trick in the strategic legal playbook.
Surprise is an important element of drama.
But surprise manufactured by witholding details of an event or by mischaracterizing a player is like a lie. It's dramatically inadequate. It doesn't work to the benefit of the story because it incurs audience resentment. Then, there's the problem of depicting children as potential killers, even though justified as the product of fundamentalist brainwashing. He would have been better advised to simply avoid this thematic and morally questionable thread because he surely didn't pull it off very well.