Warner, 40, and co-defendant Eric Deshann Floyd, 35, were convicted on July 28 for the first-degree murder of police Sgt. Stephen Liczbinski, 39.
While trying to stop the defendants from fleeing a Port Richmond bank that they had just robbed on May 3, 2008, Liczbinski was shot eight times by their accomplice, Howard Cain, 34. Police killed Cain less than an hour later.
Assistant District Attorney Jude Conroy argued during the trial that the defendants' actions demonstrated their shared intent to kill, making them as guilty as Cain.
Conroy opened the trial's penalty phase last week by presenting "aggravating" circumstances, including both defendants' long criminal histories, that he said justified death sentences.
Floyd's attorney, Earl Kauffman, last week presented to the jury "mitigating" circumstances designed to save his client's life.
He called a series of witnesses - including Floyd's mother - to speak about his growing up in a violent, abusive, drug-and-alcohol-soaked home where criminal values were instilled.
Kauffman rested his case yesterday, after Floyd told Judge Renee Cardwell Hughes that he did not want to testify.
Warner's attorney, Gary Server, called forensic social worker Roya Paller, who said Warner was born a month early to an unwed, 17-year-old mother who had little interest in raising him, Paller said. (His mother, Dolores, was in the courtroom daily during the trial.)
Warner was a poor student with learning disabilities and eventually dropped out, Paller said. In his youth, Warner was affected by having been hit and nearly killed by a car, by his mother's drinking, by her boyfriend's drunken violence toward him and her, and by unjustified beatings from his maternal grandmother, said Paller, who interviewed Warner.
Warner got into boxing in response to the abuse from his mother's boyfriend, she said he told her.
But he wasn't much of a boxer.
After a handful of pro matches, Warner was stopped for the last time during the fight shown to the jury.
He was barred from the sport after tests revealed he was no longer fit to fight, Paller said.