With an image of a real scene, I suppose it would be a defense against a child porn charge to prove that the participants were not minors. But there could be no

With an image of a real scene, I suppose it would be a defense against a child porn charge to prove that the participants were not minors. But there could be no such defense if the porn is generated. It becomes a matter for judges and juries to decide if a given picture of a person is over or under a particular age. I wonder if it would be a defense to prove that the prompt did not designate an illegal age. It may be a useful liability hedge to provably include the prompt in generated content, like as a watermark. But since existing generation isn't repeatable, and the prompt can't reliably generate the same image, is that even possible?