This thread hurts my head and I'll admit that I really only skimmed most of the posts debating sexual assault. I'm going to try to take a practical approach to this rather than touching the 'core' issue at all. Before I do, while it is a little old,
http://victimsofcrime.org/docs/DNA Resource Center/sol-for-sexual-assault-check-chart---final---copy.pdf?sfvrsn=2 goes over the statute of limitations regarding sexual assault. Very few states have limits below one year. That having been said, my wife (ADA, focused in domestic abuse and sexual assault) has repeatedly cautioned me about your exact scenario. Trying to prosecute something a year after it happens is next to impossible because ultimately it devolves into a he says, she says with year old (alcohol inhibited) eye witness testimony.
Practically speaking, I am NOT saying what is right or wrong. I am simply predicting what will happen based on what I saw happen with disciplinary issues at schools I've been at.
Reporting to the school. The best avenue will be direct interfacing with the dean of students or dean of admissions at the school. I would not do this over e-mail or phone. This is something that should be done in person. Arranged via other methods, but ultimately, the story should be told in person. There is significant rolling of the dice with doing this. For the guy, the chances of anything negative happening is very small. If he was a student when you say this happened, some schools may investigate on their own. Their standard of evidence will likely be lower than criminal courts (certainly not "beyond all reasonable doubt"), but even with that, with this much time passing, it is unlikely that anything negative will happen to the student. For you, it is also a roll of the dice. I do not think that this will help or harm you necessarily, but depending on how you present yourself during this, it may do either. If I had a daughter in your position, I would be inclined to advise her to setup a meeting with the dean of admissions and tell them in person that I was withdrawing my application to their school and explain that I couldn't fathom going to the same school as someone who assaulted me. But, I don't think that anyone can fault others for bringing things up in a different way. However, right or wrong, walking in and demanding action because "he may abuse patients one day" is going to shut down anyone that is listening to you.
Most medical schools follow similar policies to undergrads, if not identical. There is also no reason why one can't pursue criminal charges as well as have the school investigate.