The evil of court psychologists

I am thinking about writing as essay that explains all the things wrong with the way the family courts use psychologists. There are lots of books and articles that explain what's wrong with the family courts pretty well, but I haven't seen any that explain the evil of using psychologists.

For a court to ask a psychologist how I should raise my kids is about like asking an economist how I should spend my money. The supposed experts may have plenty of academic knowledge, but that knowledge says little about the choices ordinary people make every day.

Court psychologists have become like judge and jury. This article says:

You're only going to get ONE chance to do well on the Parenting Evaluation. Once the parenting evaluation is over, it's over. Evaluators almost NEVER go back and change the final recommendations in the evaluation report. To do so would open up all the previous reports they've done to reinterpretation, as well as all the future reports they're going to do.

If that's true, why do we have lawyers and judges?