JURORS at Bill Cosby’s sexual assault retrial have finished their first day of deliberations without reaching a verdict.

The jury outside Philadelphia worked more than 10 hours before calling it a night late Wednesday, local time (11.45am AEDT).

Judge Steven O’Neill told them, “Your mind is done. You’re exhausted.”

Cosby is charged with drugging and molesting a woman at his home in 2004. He says it was consensual.

Before going back to their hotel, the panel of seven men and five women had Cosby’s old deposition testimony read back to them.

The 80-year-old comedian gave a deposition more than a decade ago as part of chief accuser Andrea Constand’s civil suit against him. He testified that he gave quaaludes to women he wanted to have sex with back in the 1970s. He also testified about his encounter with Constand.

It is the first big trial of the #MeToo era, weighing charges that he drugged and molested a woman at his suburban Philadelphia home 14 years ago.

During deliberations, the jury asked a series of questions, including one that goes to the heart of the case against the former TV icon: “What is the legal definition of consent?”

The question came around 1pm local time, less than two hours after the jury began deliberating.

Judge O’Neill told the jurors he could not answer the question.

“The jury will decide what consent means to them,” he said.

Deliberations got underway this morning after a marathon day of closing arguments on Tuesday that portrayed the comedian both as a calculating predator who is finally being brought to justice and the victim of a multimillion-dollar frame-up by a “pathological liar.”

Cosby gave a quick fist pump and sashayed toward well-wishers chanting, “We love Bill!” as he arrived at the courthouse.

The prosecution and defense gave jurors lots to think about after a two-week trial pitting Cosby, the 80-year-old comedian once revered as “America’s Dad,” against Andrea Constand, a former Temple University sports administrator who testified that he knocked her out with three pills he called “your friends” and molested her at his suburban Philadelphia mansion in January 2004.

“The time for the defendant to escape justice is over. It’s finally time for the defendant to dine on the banquet of his own consequences,” prosecutor Stewart Ryan told the jury.

Cosby’s lawyers argued that the charges were based on “flimsy, silly, ridiculous evidence.” This time, prosecutors had five other women testify that Cosby drugged and violated them. One accuser asked him through tears, “You remember, don’t you, Mr Cosby?”

Cosby’s lawyers, who contend the encounter was consensual, countered by calling to the stand a woman who said Ms Constand spoke of framing a prominent person so that she could sue and extract a big settlement.

Cosby’s more streamlined first trial ended in a hung jury last year after deliberations over six days.

Only one additional accuser testified that time.

Nor were jurors told the amount of Cosby’s 2006 civil settlement with Ms Constand: nearly $US3.4 million ($A4.5 million), which defence lawyer Tom Mesereau on Tuesday called “one of the biggest highway robberies of all time.”

“I have never seen or heard of a retrial that was as different as this was from the first trial,” said lawyer Dennis McAndrews, who has been following the retrial and is not associated with either side. “The prosecution now had multiple victims and the defense had the issue of money, which were powerful weapons for both sides.”

Cosby faces three counts of aggravated indecent assault, each carrying up to 10 years in prison.

His wife of 54 years, Camille, looked on from the gallery as his lawyers pleaded with the jury to clear him, the first time she has attended the trial.

She also sat in for the defence’s closing argument at his first trial.

Camille Cosby, 74, had stayed away as the prosecution built its case that her husband maintained a sordid double life, plying women with drugs and preying on them sexually. Before the jury came in, she put her arm around Cosby, who is legally blind.

They smiled and chatted, and he gave her a peck on the cheek.

When it was the prosecution’s turn to argue, she left the courtroom, and Ms Constand entered.

“You’re dealing with a pathological liar, members of the jury,” said Mr Mesereau, who won an acquittal in Michael Jackson’s 2005 child molestation case. “You are.”

Prosecutor Kristen Feden called Cosby the true con artist - wresting that label from Cosby’s lawyers, who had applied it to Ms Constand throughout the trial.

“Yes, you did hear about a con,” Ms Feden said, her voice rising as she moved toward Cosby and pointed at him. “The perpetrator of that con is this man, sitting right here.”

She warned that the man trusted for his role as genial, sweater-wearing Dr. Cliff Huxtable on The Cosby Show is “nothing like the image that he played on TV.”

The defence highlighted more than a dozen inconsistencies in what Ms Constand has said over the years and painstakingly reviewed phone and travel records, saying they prove the alleged assault couldn’t have happened when she says it did.

They also argued that he was charged after the 12-year statute of limitations for prosecuting him had run out.