The case will not disappear after a few years. If your friend does not appear he will continue to have a warrant hanging over his head in Arizona indefinitely. It is not clear from your question, but this DUI may have been charged as a felony DUI, since there was a suspended license involved. If this is a felony DUI, then he could be arrested on the warrant in Indiana (or any other state) and extradited back to Arizona. The misdemeanor DUI sentencing enhancements are not retroactive so, if this is a misdemeanor, he would be looking at the penalties under the old law. There have not been any recent substantial changes to the felony DUI statutes. DUI