Bob Sheridan - who is really coming into his own as a blawgger - has written an excellent article on false accusations in child abuse and molestation cases, entitled "Fooling Ourselves: Cargo Cult Law and Medicine."
The first principle is that you must not fool yourself — and you are the easiest person to fool (Feynman, 1985).
ABSTRACT: A fundamental cause of false accusations is the tendency of adults to fool themselves. Adult investigators who are biased towards believing an accusation is true will be unable to conduct an appropriate investigation and therefore will find what supports their prior beliefs.
So many child sex accusations turn out false that I have wondered why presumably intelligent and well-meaning authorities believed them in the first place. False accusation fiascos have included McMartin Preschool, Morgan-Foretich, the Jordan, Minnesota case, and the Cleveland, England affair. In my practice, a six count case (worth 23 years in prison) was dismissed before trial last April after the client spent three months in jail and a 61 count case was dismissed after a hung jury a few years ago; both were false allegation cases.
I encourage you to read the full article.