Upon seeing a pre-screening of the film, Jodie Foster thought her performance as Sarah Tobias was so awful that she immediately began preparing for and taking the GRE's for graduate school. She was prepared to leave her film career behind and focus on academia...until she won the Academy Award for her performance.
Kelly McGillis was offered the role of Sarah Tobias, but having survived a violent sexual assault in 1982 by two men who broke into her apartment, she declined the role and instead fought for the part of Kathryn Murphy.
Jodie Foster has since acknowledged that she purposely gave a trite performance in her audition so that Paramount executives would feel that she was a safe choice. Foster had been going through a bit of a dry spell at the time and badly needed a big role in a mainstream movie. It was only after Kelly McGillis - then a hot property due to the enormous success of Top Gun (1986) - signed on that Paramount would even consider letting Foster play Sarah, since the studio didn't believe this film stood a chance if neither of its stars had box-office clout. (Foster and McGillis were rumored to have been girlfriends at the time, and it was at McGillis's insistence that Foster be given a chance to try out.)
In their separate careers several years after the release of The Accused (1988), both leading ladies, Kelly McGillis and Jodie Foster, publicly and proudly acknowledged their homosexuality. McGillis came out in 2009, and Foster in 2013.
The trivia item below may give away important plot points.
In an interview, Jodie Foster explained that the rape scene was meticulously rehearsed beforehand, so there would be no unpleasantly surprises for anyone involved in the actual scene. Even so, one of the male actors had to vomit in disgust during the shooting, and Foster herself has admitted that she does not remember filming the scene, so she must have blacked-out.