Would a so-called consent contract for BDSM , which was voluntarily?
Nope. In addition to what John VanValkenburg says in his answer, theres another component as well: Sexual consent exists only in the moment and can always be revoked. You can sign a contract in front of a camera and have the entire Supreme Court notarize it and the moment you withdraw consent, its null and void. That said, in the US, there has never to my knowledge been a successful rape prosecution against a person who engaged in voluntary BDSM with the victim beforehand. This is a matter of US culture and sex-negativity, not a matter of law. She must have wanted it, she did kinky things with him is this generations she must have wanted it, just look at that dress!