The 79-year-old pioneering black actor could face spending the rest of his life in prison if convicted on three counts of aggravated indecent assault against 44-year-old Andrea Constand at his Philadelphia mansion in January 2004.
The 12-member jury told Judge Steven O'Neill Thursday that they were deadlocked, but the Pennsylvania judge ordered them to continue with no cut-off point to stop trying to reach a unanimous agreement.
Under US law, any application of the term "reasonable doubt" would mean that the jury should acquit the defendant.
The panel also asked to hear excerpts from Cosby's deposition in 2005 in which he says he gave the sedative Quaaludes to a woman in Las Vegas in 1976 before having sex with her, and that he used them with other women.
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The agonizing wait for a verdict saw tensions rise Friday outside the court in Norristown, just outside Philadelphia.
Although the trial concerns only Constand's allegations, 60 women have publicly accused the legendary entertainer of being a serial sexual predator in remarkably similar accusations that span four decades.
The trial marks a steep fall from grace for an entertainer known for his role as a lovable father and obstetrician on hit TV series "The Cosby Show."
The avalanche of allegations have already ended the career and pulverized the reputation of a comedy legend who turns 80 next month.