Norristown (United States) (AFP) - A Pennsylvania jury was set to deliberate a fourth day Thursday, still deadlocked on whether to convict disgraced megastar Bill Cosby of committing sexual assault more than 13 years ago.

The 79-year-old pioneering black actor could face the rest of his life in prison if convicted on three counts of aggravated indecent assault for allegedly drugging and molesting a woman at his Philadelphia home in January 2004.

The 12-member jury began deliberations on Monday and has worked late on three consecutive nights. They are being sequestered for the duration of what is one of America's biggest celebrity trials in years.

While they have asked the judge questions and requested testimony from Cosby, his accuser and the police to be read back to them, it remains unclear how close they may be to reaching a unanimous decision.

They are set to resume deliberations at 9 am (1300 GMT) on Thursday.

The maximum penalty for each charge is 10 years in jail and a $25,000 fine. But there is no mandatory minimum, meaning that the judge overseeing the case could also allow him to walk free.

The trial marks a steep fall from grace for an entertainer for decades loved by millions as "America's Dad" for his seminal role as a lovable father and obstetrician on hit TV series "The Cosby Show."

In closing statements, the prosecution portrayed the actor as a sexual predator who deliberately drugged 44-year-old Canadian Andrea Constand so she would be unable to resist his advances at his Philadelphia home.

Cosby refused to testify and his lawyers called just one witness, a police detective, before resting their case minutes later on Monday.

Around 60 women have publicly accused the Emmy-winning comedian of being a serial sexual predator in remarkably similar accusations that span four decades, ending his career and pulverizing his reputation.

Constand's is the only criminal case against him as under US law, most of the alleged abuse happened too long ago to prosecute.

If the jury ultimately fails to reach a verdict, the district attorney will be given the option to request a re-trial.

But if Cosby is convicted, even on one count, Montgomery County prosecutors will probably petition for his $1 million bail to be overturned and that he be taken into custody immediately.