Much depends on many factors, some of which aren't mentioned here. To really know percentage chances of winning I'd need to see discovery. As you know, these are serious allegations. You should contact a criminal defense attorney at once.
-Attorney Scott Aaronson
877-I-CAN-WIN (free consultations)
Legal cases are not like dice games where you can calculate the odds of rolling a particular number. Instead, the chances of winning will depend on many factors, possibly including credibility of the accuser, credibility of the defendant if he testifies, out of court statements by the defendant or witnesses, other evidence for or against the defendant, and legal rulings which allow or forbid certain things during trial.
Normally, a past conviction for a sex offense would not be admissible into evidence, unless the defense opens the door to the evidence by bringing it up as a factor causing the police or complainant to complain against the defendant. Avoiding that would probably be a major goal of the defense.
In some cases testifying is a wise idea for the defendant, in other cases not so wise.
I do not understand how the witness could not want to press charges, but would call the police anyway. If she did not want sex, but did not want to prosecute, why did she just not ask the defendant to leave? If she called the police because the defendant refused to leave, that would be important evidence against the defendant.
You need to consult with an experienced criminal defense attorney. If you have all the discovery (police reports and similar documents) from the case, you can call my office and arrange an appointment for a free consultation. I caution you that it will cost money to hire an attorney to take a case to trial, but that cost might be insignificant next to the costs associated with being convicted of another crime. But, if you have no money, the court will appoint an attorney for you.
Indecent exposure would normally be a misdemeanor, tried in district court. In my experience, the judges of the court in Farmington Hills are fairer than those of many neighboring district courts, which is good if your case is from there. On the other hand, the nearby court in Bloomfield, West Bloomfield and Birmingham, on average, is much less favorable to the accused. Which court and which judge you have will play an important role in the outcome of the case.
Contact me at 248-399-6930 for a free consultation. You and I do not have an attorney-client relationship formed by our communications on this website. Advice given by me on this website is general advice based on partial information. You should not rely on any advice given without first hiring a lawyer in the area where the case is pending, and providing that lawyer with full information.