By Jasper Ward and Kanishka Singh

Former University of Southern California campus gynecologist George Tyndall, who was accused of sexually assaulting patients under the guise of treatment or exam, has died, his defense attorney said on Thursday.

Tyndall's lawyer, Leonard Levine, told Reuters on Thursday that a close friend found Tyndall unresponsive after he failed to return that friend's phone calls the day before.

"All he ever wanted was his day in court, which he was confident would end in his complete exoneration," Levine said, reiterating that his client had denied all allegations against him. He also added that the cause of death was likely natural and Tyndall seemed to have died in his sleep.

Tyndall lost his medical license and had been charged with sexually assaulting 21 patients under the guise of gynecological treatment or exams.

A Los Angeles Superior Court judge ruled that prosecutors had presented sufficient evidence for him to stand trial, which was expected to begin next year, the L.A. Times reported in August.

"Now, neither he nor his accusers will get that, and that is very unfortunate for everyone involved," Levine said on Thursday.

(Reporting by Jasper Ward and Kanishka Singh; Editing by Caitlin Webber and Lisa Shumaker)