The jury picked for the death-penalty case must now decide if the slaying was premeditated or whether 21-year-old John Lewis panicked when he saw Officer Chuck Cassidy enter the store.
Cassidy, 54, is remembered as a warm, devoted community servant who was raising three children with his high school sweetheart and made daily rounds at small businesses on his beat in North Philadelphia.
He and Lewis, both armed, walked some of the same streets and entered the same stores, one to protect and the other to terrorize, prosecutors said Thursday.
"So it's not all that surprising that the lives of these two men would cross," Assistant District Attorney Jennifer Selber said in opening statements.
Lewis, now 23, nervously misstated his name before uttering the word "guilty" to a dozen robbery, weapons and assault charges, and finally to the murder charge. The Cassidy family and the phalanx of police officers around them seemed to wonder what they had heard. But the pained sobs of Lewis' family members confirmed the plea.
Lawyers had spent four days last week picking jurors willing to consider the death penalty. The jury must now decide whether Lewis committed first- or second-degree murder, the latter being an unplanned death that occurs during a crime.
Cassidy's death was one of a string of police slayings that have rocked Philadelphia since mid-2006, with at least seven officers killed on duty.
Faced with devastating security tapes from the robberies and Lewis' confession to news crews after his Nov. 6, 2007 capture in Miami, defense lawyer Michael Coard conceded his client's guilt. Police also found his gun - and Cassidy's service weapon - stashed at a cousin's house.
"A hero died at the hands of John Lewis," Coard said.
Still, he said the rage and sadness inherent in the case does not alone merit a first-degree verdict.
"That can't carry the day," he said. "Was it a calculated, premeditated plan to kill a police officer, or a panicky reaction during a robbery?"
Selber found premeditation in the two steps that Lewis took toward Cassidy, who had crouched down and was shot in the head from above. She called the murder "inevitable" given Lewis' increasingly brazen six-week crime spree.
The boyish-looking thief who had nervously waved a gun in the initial Sept. 18 robbery was by Oct. 25 hopping the counter at a busy pizza parlor and pistol-whipping employees.
"He was moving along a path. He was flirting with murder," Selber said.
Eerily, Cassidy had pursued Lewis after the Sept. 18 robbery, which occurred at the same Dunkin' Donuts store where he would be shot Halloween morning. With help from a witness, Cassidy recovered a sweatshirt the robber had tossed aside. After his death, DNA tests would link the shirt to his killer.
Although a gag order prevents lawyers from discussing the case, Lewis could presumably still face the death penalty if convicted of first-degree murder. The son of a correction officer, he said Thursday that he quit school in 11th grade and has been treated in prison for mental-health issues. The robberies netted him a few hundred dollars apiece.
"He robbed a wife of her husband, he robbed three children of their father, and indeed robbed an entire city of a great man," Selber said.