After reading your first post again, I feel I should also point out that you're saying he was engaged to another girl? And he's groping somebody who isn't his fiancee? Never mind that that's cheating, you didn't even want him doing that, so he's doing TWO wrongs there.
The main reason that a lot of sexual assaults and rapes go unreported is because the victims don't want to have the entire thing made public and because they'll have to talk about it over and over again. And I don't blame anybody for hating that, it's terrible. But if you don't say anything, he would've gotten away with this, and who knows what he would have done to someone else, maybe even this other girl.
The worst thing in the world you can do right now is claim you made the whole thing up. For one thing, that makes you look like a total monster, and the guy's reputation will STILL be tarnished whether he's acquitted or not. For another, making false allegations is a crime in itself. If you didn't make it up, why put yourself in jail instead of this guy? If you really, truly believe he doesn't deserve to suffer as much as he will, then ask to speak with the prosecutor about leniency for him.
Edited by mremaknu, 12 January 2011 - 05:46 PM.