If you're accused of sexual assault, it's within your rights to defend yourself from the moment of accusation. It's not fair for a person to accuse you of assault if you didn't assault them, and even though the statistics might be weighed against you, the court can't have a bias.
One thing that might help in your case is the statute of limitations law. Once the time period for filing a case ends, the alleged victim can no longer pursue a criminal trial. In most situations, the limit is two years, although that can vary and should be something you talk to your attorney about.
Another thing to recognize is that not all cases end up in court. You may be able to settle the case out of court, especially if your attorney can convince the prosecution that there isn't enough evidence to pursue the claim. It falls on the victim to prove that you committed a crime, so if there's any chance that the prosecution won't win in court, it's more likely that the attorney will try to settle with you early. Of course, if you can prove you didn't commit a crime, you could have the entire case dismissed.
In criminal court, there is a higher standard of proof, which means the victim needs to prove beyond a reasonable doubt that you committed a crime. Even if you go to trial, if you can put doubt in the minds of the jurors, you can potentially walk away without a sentence. Your attorney can help give you a good idea of what to expect after reviewing your case.
Source: Teen Vogue, "5 Things Every Young Woman Should Know About Sexual Assault Laws," Polly Mosendz, accessed Dec. 23, 2016