First, Judge Steven O'Neill sent them back into deliberations in another attempt to reach a verdict, which must be unanimous. Cosby, 79, has pleaded not guilty to three charges of aggravated indecent assault.
"I am required to read you an instruction. The jury foreman has informed me that you are deadlocked," O'Neill said. "If you are still deadlocked you should report that to me. If you've reached a unanimous decision on some of the charges, please report that back to me."
There is no rule on how many times O'Neill can order jurors back to work under the Spencer Charge.
The jury could come back with a verdict
After further deliberations, jurors could still return a unanimous verdict. There are three possibilities:
-- Guilty on all counts.
-- Not guilty on all counts.
-- Mixed verdict, finding guilty on some charges but not guilty on others.
Jurors can also return a partial verdict, in which they come to a unanimous verdict on some counts yet deadlock on other counts.
The three charges accuse Cosby of assaulting Andrea Constand without her consent, assaulting her when she was unconscious and assaulting her using drugs to substantially impair her ability to consent. If found guilty, he could face up to 10 years in prison for each charge.
The 12-person jury is made up of six white men, four white women, one black man and one black woman. They were bused in from Allegheny County near Pittsburgh and have been sequestered in a hotel for the trial.
Mistrial could be declared
If the jury tries again and is still deadlocked, it would be considered a "hung jury" and opens up the possibility that O'Neill will declare a mistrial.
In that case, Cosby would not be found guilty, nor would he be acquitted. After the declaration of a mistrial, prosecutors may choose to retry the case with a different set of jurors, or they may cut their losses.
Prosecutors say Cosby drugged and sexually assaulted Constand, a former Temple University employee, at his Pennsylvania home in January 2004. The case has little forensic evidence, and legal experts have said it fits the "he said-she said" dynamic that is common to sexual offense cases.
The trial began on June 5, and the jury began deliberating Monday evening. After 31 hours of deliberations, jurors said they were deadlocked.