Happen to us before. One way is, we check CCTV. Another way is, we use her to near the guy again and watch from far if he touch her intentionally. The 2nd way kinda scary but if she wants to proof it she has to be brave. I think the 2nd way is not at all a viable way to do it. As I'm sure the person who has filed this case, has been through enough TRAUMA, and to put her into a situation like that again will be disastrous, if not for her safety, then her mental health.But before u suggest the second option, u need to make sure the victim understand the consequences of 2and option. You should also look into having Sexual Harassment training for the company. Other than that, you may also get a middle person to speak to both parties to find out why this happened. Maybe it was an accident or maybe it was something much more devious. The women should NOT by any circumstance be forced to confront her supervisor - this might make things worse. Either way, talking to both parties would help find out why this happened. And then provide counselling for the person who received the sexual assault (btw its considered assault and not just harassment as there was touching involved), and provide assurance for her safety by either changing her supervisor / terminating him (if proven guilty).