On Thursday, the 12-person jury announced that it was unable to reach a unanimous decision after nearly 30 hours of deliberation but were sent back to the negotiating table by the judge.
Prosecutors argued Cosby drugged and sexually assaulted Constand at his home near Philadelphia in 2004.
The judge in the sexual assault case of comedian Bill Cosby has declared a mistrial.
Jurors worked into the night Thursday after Judge Steven O'Neill told them to try and resolve the impasse. As a result of Constraint's accusations, Cosby has pleaded not guilty and continuously denied any wrongdoing.
Since Monday, jurors - consisting of seven men and five women - have been attempting to reach a unanimous decision on whether Cosby is guilty of three acts of aggravated sexual assault against Andrea Constand.
After deliberating for four days and rereading and hearing testimony, the jury has been unable to come to a conclusion.
Celebrity lawyer Gloria Allred, who represents several women who have also accused Cosby of sexual assault, said that jury deadlocks were not unusual and that she was not frustrated by the deadlock.
Cosby is accused of drugging and molesting Andrea Constand in 2004.
After trying to shout down the Cosby accusers they appeared to be gaining the upper hand when a sexual abuse supporters group drowned them out.
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Constand's lawyer, Dolores Troiani, said only that the "jury is apparently working very hard". He says he believed a chat with the family from Plymouth Meeting would brighten Cosby's spirits.
In court Thursday, O'Neill read to jurors the Allen Charge, also known as the "dynamite charge", which is a set of instructions that asks jurors to re-examine their own views and opinions. They wanted to know what is "reasonable doubt".
"Hey!" to Cosby as he enters the courthouse every morning, to the woman shouting "We've already won!" while driving a U-Haul truck with an anti-sexual assault message, there's plenty for the myriad of news organizations covering the trial to see.
As the rhythmic drumming continued, Victoria Valentino, a former Playboy bunny from the 1960s who says Cosby assaulted her decades ago, danced to the music on the courthouse steps. All the defense has to do is create a reasonable doubt in the jury's mind that Cosby is maybe not a serial rapist.
As the jurors left for the day, O'Neill heaped praise on them, thanking them for their dedication and the sacrifice they've made being 300 miles (480 kilometers) from home in the Pittsburgh area. Constand's case was the exception.
Theyre conflicted about the inconsistencies in Ms. Constands testimony, spokesman Andrew Wyatt said. In it, Cosby admitted to giving her pills; he said they were Benadryl to help her relax.
Cosby faces up to 10 years in prison on each of the three counts, but they could be merged for sentencing purposes.
She became incapacitated and felt "frozen" and told him so, Constand testified. Some of them looked defeated as the judge sent them back to the jury room.