The jury is deciding whether Rasheed Scrugs, 35, would get life in prison or the death sentence for killing Officer John Pawlowski.
On Friday afternoon they told the judge they could not come to an agreement.
The judge has allowed the jury to go home for the weekend and return to deliberations on Monday.
The judge says some of the jurors seem to be unclear on the law.
Scrugs pleaded guilty to first degree murder as his trial was about to start in October.
The court was stunned as Scrugs went on to apologize for the killing.
Closing arguments in the sentencing hearing were held on Tuesday.
The killing of Officer Pawlowski happened in February, 2009 at Broad and Olney.
Prosecutors said Scrugs threatened a cab driver, then threatened to shoot police who arrived if the cabbie alerted authorities.
When officers did arrive, police say Scrugs shot the 25-year-old Pawlowski in the chest after being ordered to take his hands out of his pockets.
Scrugs was also wounded in the resulting shootout and arrested at the scene.