Some potential witnesses who attended the parties where the alleged sexual assaults occurred are refusing to talk with his defense team, the lawyer said. He would not say how many witnesses.

The motions will be filed under seal, Nemann said.

Lawyers for both defendants have said their clients are not guilty of the charges.

"We deny the accusations completely. We deny the lack of consent. We deny that there was sexual activity. We deny that there was a rape. And we steadfastly maintain that," Nemann told CNN.