Then what IS the way of going about proving it?
You have expertise in this area I take it?
What did they do wrong and what would you have done right?
The way of going about proving what was going on at the compound is to do it LEGALLY, in a constitutionally sound way.
I have had some experience in trying to prove these types of allegations and I know how difficult it is to prove, but failing to follow all the rules only does more damage in the long run to the very people that you are trying to protect, AND the perpetrators get off with nothing more than the hassle of the accusations.
The authorities could have used every legal means of entering that compound and made their presence a common occurrence. They could have used fire inspections, health dept inspections, department of education visits. They could have questioned the innoculation records and things like that, that would have required signatures of the parents. There is so much that the authorities could have done that would at least have deterred any violence against the children, because it would have lessened their isolation.