1. This assumes that judges (priests) are honest and neutral to the case, and doesn't believe in the intervention of God themselves.<p>2. This assumes people innocent in this case won't be afraid God won't help them because of theirs other sins (and who is not a sinner?).<p>3. I don't think people were that much religious then. I mean - sexually medieval people wasn't more puritanical than we are, why should we assume they were believing in God thah strong (to put hand in the fire etc).<p>4. How do we know ordeals worked? It's obvious that priests were describing their work in superlatives. And they were the most literate class then.
"The only defendants who would have been willing to go through with the ordeal were therefore the innocent ones."<p>This only works if the guilty would in fact face lesser punishments than the ordeal, including the social penalties for having been found guilty. Considering how brutal medieval punishments were, this seems unlikely.