If the accused commits a crime that is similar in 'time, place, and circumstance', to the current indictment, then evidence of that past behaviour can be heard. It's called the Moorov doctrine, following
So if Jack (an employer) is accused of sexually assaulting Jill (his employee) at their office, during working hours; then if Janice gives evidence that she was also a victim under substantially similar circumstances, then Janice's evidence can be used to indirectly corroborate Jill's accusation and lead to Jack's conviction.