What does it mean to be 'accused of sexual assault' for purposes of Federal Rule of Evidence 413, and when can such evidence be admitted in a criminal trial?

Petitioner Arjune Ahmed was convicted of two counts of kidnapping. The district court declined to give him separate trials on the two kidnapping allegations , even though the allegations involved different victims and distinct events . Additionally, the district court admitted over his objection evidence that he had committed a sexual assault for which he was not charged. The court made both important decisions based on its interpretation of Federal Rule of Evidence 413, which provides that “[i] n a criminal case in which a defendant is accused of a sexual assault, the cour t may admit evidence that the defendant committed any other sexual assault. ” This case presents an issue that has split the circuits: W hat does it mean to be “accused of sexual assault” for purposes of Rule 413? Does it mean that the defendant is charg ed with an offense with an element requiring proof of sexual assault? Or is a defendant “accused of sexual assault” whenever a prosecutor informally alleges that he committed a sexual assault, regardless of the elements of the charged offenses?