The announcement of a "hung jury", as it's known, leaves the possibility that O'Neill will declare a mistrial.
The judge's decision was echoed by Gloria Allred, Constand's lawyer, who snapped at Wyatt for pushing for mistrial.
Prosecutors say Cosby drugged and sexually assaulted Constand, a former Temple University employee, at his Pennsylvania home in January 2004.
In court, the judge then read a new charge to the jury and told them to go back and continue their deliberations.
Cosby denies the allegations; he declined to testify in his own defense at trial. In that case, prosecutors would get four months to decide whether they want to retry the TV star or drop the charges.
The judge did not set a deadline for how much longer the group should deliberate on the three counts of aggravated indecent assault, a charge that carries up to 10 years in prison.
The jury deliberations have stretched across four days.
Tensions ran high on the Montgomery County Courthouse steps Thursday afternoon after news of the deadlocked jurors broke.
In it, he claimed Constand showed no ill effects from the 1½ Benadryl pills he gave her to help her relax and that she never objected to his behavior during the encounter. During the statement, Cosby admitted to giving his accuser, Andrea Constand, blue pills before they engaged in what he described as "heavy petting".
Theyre conflicted about the inconsistencies in Ms. Constands testimony, spokesman Andrew Wyatt said. Allison held the woman's hand as she tried to persuade her to change her mind and told the woman she would have had the same opinion if she had never been alone in a room with Cosby.
Count one is the matter of consent: did Andrea Constand say "yes" to engaging in sexual contact with Cosby? Prosecutors would have the option of seeking a retrial if the jury can not reach a verdict. Jurors could say that Cosby is guilty of one, two or three of these counts.
Thursday morning, the jury of seven men and five women from Allegheny County arrived at the courthouse about 9 a.m. and went straight into deliberations.In addition, the six alternate jurors are still in Norristown, but they are not involved in deliberations.
On Thursday afternoon, Bernard confronted a man outside the courthouse who Philadelphia Inquirer reporter Laura McCrystal identifies as a Cosby supporter.
Bill Cosby acknowledged fans in a freakish fashion on Tuesday night by shouting out in the voice of his classic Fat Albert character while leaving a Pennsylvania courthouse.
"We had worked so hard, sacrificed so much and prayed so much and didn't sleep enough and didn't eat enough".
"It's not over until it's over, and it's not over yet", she said.
- US Warns Syria Preparing Another Chemical Attack, Threatens Retaliation
- US says Myanmar no longer among worst on human trafficking
- It was heartbreaking to leave Ant-Man: Edgar Wright
- Minimum wage killing Seattle jobs, according to UW study
- Key Takeaways from CBO Score of the Senate's ACA Replacement Plan
- Another leadership test for Pelosi, who's weathered many
- Opposition's Presidential Candidate Meira Kumar To File Nomination On Wednesday
- Jeremy Corbyn gets rock star welcome at Glastonbury Festival
- Freed US student `brutalised´ by North Korea captors - father
- Russell Westbrook named NBA's MVP after record-setting season