Candy, there's a difference between an accusation and being charged with the crime itself. For my benefit, is it possible that someone is alleging your client raped someone (possibly even the victim) but he hasn't been charged? The reason I ask is that there has to be evidence to support a charge and as his defense attorney you would have access to that evidence and know how to proceed in the best interest of your client.
On the other hand, if some person is going around accusing him of rape (to his friends possibly) and he's looking for a way to prove he didn't do it, it's strictly his word against hers and that's the end of it unless she brings charges against him.
Have you considered consulting an attorney with some experience in this area?