Lots of things cannot be resolved short of trial. If there isn't a question of law, then there is only a question of fact. If the accusation made - if the facts alleged in the complaint, if proven true, are sufficient to support a guilty finding then the case cannot be dismissed on that basis (referred to as a 3G motion). If there is no basis for suppressing any evidence, that evidence would be allowed provided that it is relevant and its probative value exceeds its prejudicial value. So that brings us to a trial. The evidence is nothing more than the accusation from the alleged victim. There are no witnesses or any independent evidence (photographs, video recordings, marks, etc.). The complaining witness gives their testimony, the defense attorney cross examines. The finder of fact, whether it be a judge or a jury, will then weigh the evidence, and the credibility of the witness and apply the law as instructed. Without a sufficient basis to dismiss a case, we are stuck waiting to go to trial on what is typically nonsense.