They had been deliberating for roughly two hours Thursday - about 30 hours overall - when they reported after 11 a.m. that they were deadlocked and could not reach a unanimous decision on any of the three counts that have been filed against Cosby.
Judge Steve O'Neill sent the jury back. Judge Steven O'Neill gave them instructions to try again, issuing a "dynamite charge" or "Allen charge", meant to motivate an uncertain jury to reach a decision.
Bill Cosby (R) arrives on the fourth day of jury deliberations of his sexual assault trial at the Montgomery County Courthouse on June 15, 2017 in Norristown, Pennsylvania.
Constand was the prosecution's key witness, telling jurors that Cosby gave her three unidentified pills before taking advantage when she was disoriented to sexually assault her.
Andrea Constand, who has accused Cosby of drugging and sexually assaulting her in 2004 at his Pennsylvania townhouse, tweeted a slow-motion video of herself shooting a ideal basket in what appeared to be the hallway of the courthouse where the jurors are deliberating.
Cosby's lawyers maintain Constand was a willing sexual partner.
Cosby, the 79-year-old entertainer once beloved for his brand of family-friendly comedy, is accused of drugging and sexually assaulting Constand, then 31, at his home near Philadelphia in 2004.
Cosby, of Cheltenham, has been on trial for nine days and charged with three counts of aggravated indecent assault.
If the former comedian is convicted, Cosby could face a maximum of thirty years in prison.
On Thursday, the jury entered into its fourth day of deliberations - and announced that it can not arrive at a unanimous decision despite extended deliberations.More news: Juventus join contest for Gunners defender Hector Bellerin
Referring to the "emotional and physical toll" of the trial on Cosby, Wyatt said the judge should declare a mistrial since the jury has already exceeded Montgomery County record for deliberations.
If a mistrial is declared, prosecutors must decide if there is enough evidence to seek a new trial or decide to drop the charges.
O'Neill's instruction to the group to keep working was delivered as part of what is known in Pennsylvania as "Spencer Charge" - a last admonition to the jury that it is important to reach whatever verdict it can in a given case.
At around the same time, Attorney Gloria Allred who is defending some of the alleged victims said she is not losing hope.
The trial comes after repeated efforts by Cosby's lawyers to have the charges thrown out.
The sequestered jurors have appeared increasingly exhausted and upset after deliberating late into the night the past three days.
As court proceeding came to a close Thursday, the jury forewoman said the members could not reach "a unanimous consensus on any" charges against Cosby. Their assertions span five decades and several had similarities: the accusers said the alleged assaults occurred in conjunction with Cosby's giving them pills.
The case has helped demolish Cosby's nice-guy image, cultivated during his eight-year run as Dr. Cliff Huxtable on the top-rated "The Cosby Show" in the 1980s and '90s. His lawyer has said they were lovers sharing a consensual sexual encounter.
Ms Constand and her mother were in court for the announcement from the jurors.
Constand won a national title with the University of Arizona and played in a pro league in Europe before landing a job with Temple University women's basketball team.