I assume from what you've said that your sexfriend got charged with Assault Bodily Injury - Family Violence. All that is necessary to prove this charge is that there was nonconsensual bodily contact, that that contact resulted in bodily injury, which is defined as a physical impairment, visible injury, illness, or complaint of pain, and that the defendant and victim were now or in the past in a romantic, dating or sexual relationship. This charge is also applied to roommates and family members, but I am guessing from your use of the term sexfriend that these are not directly applicable.