If you are truly innocent, get the very best lawyer you can afford, someone specializing in suing universities and colleges. If your appeal is denied, you can always sue in state or federal court and call witnesses. It may not get you re-admitted, but if you have a libel or slander case, you could get damages. University appeals are notoriously unfair. Contrary to popular belief, universities are not immue from state and federal laws. Sure they can have their own disciplinary procedures, but they cannot deny you due process of law.