(Reuters) - A judge ruled on Friday that a second woman who said comedian Bill Cosby sexually assaulted her would be allowed to testify at his upcoming trial in Pennsylvania on charges he sexually assaulted a former employee of Temple University.

About 50 women have accused Cosby, 79, of sexual assault. But the accusation from 2004 by Andrea Constand, the former university employee, is the only one to result in a criminal prosecution.

Cosby has denied any wrongdoing, but the accusations have shattered his image as an icon of family-friendly entertainment.

Constand worked with the women’s basketball team at Temple University, where Cosby, a university alumnus, befriended her. She says Cosby drugged her and sexually assaulted her when she visited him at his home in Pennsylvania. Cosby says the encounter was consensual.

Montgomery County prosecutors had asked in December to have up to 13 other women who have accused Cosby speak at the trial as “evidence of prior bad acts,” arguing it showed a pattern of behavior. Cosby’s defense lawyers fought the request, calling it a “bandwagon” of uncorroborated accounts.

Judge Steven O’Neill of the county’s Court of Common Pleas ruled that only the woman identified as Prior Alleged Victim Six should testify.

She worked as an assistant for one of Cosby’s agents in the 1990s and said she became friends with him, according to prosecutors. She said Cosby invited her to lunch in 1996 to discuss her career, but instead forced her to swallow a pill before sexually assaulting her while she drifted in and out of consciousness.

Evidence of “prior bad acts” is typically disallowed to avoid unfairly prejudicing jurors. But prosecutors can be permitted to introduce such evidence if it shows a clear pattern of behavior.

“This ruling is important as the jury will now be allowed to assess evidence that is relevant to establishing a common plan, scheme and design of sexual abuse and an absence of mistake by the defendant,” Kevin Steele, the county’s district attorney, said in a statement.

Andrew Wyatt, Cosby’s publicist, declined to comment on the ruling.

The court will hold a hearing on Monday on Cosby’s attempt to change the venue of the trial.