When they were adults and free to leave.
If they had been 12 I would be a little more inclined to think there might be something to their tale of woe.
But this was a murder for money pure and simple.
Starting to remember that trial now, they were older HS kids or recent grads at the time, physically capable young men, access to lux cars and $$$$, elite schools, etc., when they murdered their parents.
Agreed, big diff between a 11 or 12 year old fighting back and a 17-20 year old with a shotgun.