At the Pew Forum, professor Robert Tuttle is interviewed about the intricacies of the law in the area of parents who refuse medical treatment. Here, he lays out the basic consideration of religious exemptions.
When an exemption clearly and specifically protects the practice of faith healing, parents have been successful in using the exemption to defend against criminal charges, even in cases in which the child has died.
But in states that have an unclear exemption that may or may not apply directly to the conduct in question, parents have been less successful in claiming that their belief in faith healing protects them from criminal charges. Nevertheless, parents still have prevailed in some of these cases because courts generally interpret legal uncertainty in favor of the criminal defendant.