My question involves criminal law for the state of: Texas

If a statutory rape charge were filed against an 18 year old male, the girl being 15 years old, what would happen? What process would take place after the charges are filed? Does there have to be evidence if it goes to court? The girl is a bit more than 3 years in age difference, so Romeo and Juliet laws wouldn't work, at least I don't think they would. What exactly can the male use as defense? If the parents press charges, do they need evidence? How can it be proved that intercourse took place if there are no witnesses in any form? I'd like all of the information I can get.