Non bis in idem

A violinist, Aurélie Chataignier, comes to file a rape complaint. She accuses her conductor, Vincent Lemeur. As the investigators have little evidence to support their investigation, the young woman brings them the filmed confessions of Lemeur, who acknowledges having raped her six months ago. However, the case had already been tried with the same protagonists, for the same reason and Lemeur had been acquitted. Investigators are at an impasse: one cannot be tried twice for the same crime when one has been acquitted. How can justice defend a just cause without having the legal means to do so ?