Kaboni Savage should die, a prosecutor said Tuesday, because he wantonly slaughtered children and witnesses, and because he laughed about it and vowed that even prison could not stop him from plotting more deaths.

"The fight don't stop 'til the casket drop" was his mantra, Assistant U.S. Attorney David Troyer told a federal jury.

The drug kingpin should live, Savage's lawyer countered, because his past was shaped by tragedy in a North Philadelphia neighborhood overrun by crime and drugs, and because even a life of solitary confinement in a tiny windowless cell might make a difference.

"Despite that cement box, there could be some good, some light, that comes out," said William Purpura.

Those were the options for jurors as they began weighing the penalty against Savage, convicted last week of 12 murders, including the 2004 North Philadelphia rowhouse firebombing that killed four children and two adult relatives of a witness against him.

The sentencing phase, expected to last at least a week, will unfold with arguments and evidence like a mini-trial, U.S. District Judge R. Barclay Surrick told the panel. But the structure and legal standards are different.

First, the nine women and three men must decide whether Savage's crimes are egregious enough to meet aggravating conditions that make them worthy of the death penalty. Then they must vote on whether he deserves it.

If Savage was troubled by the options, he chose not to show it. As one lawyer pleaded for his death and another described how miserable his life would be in a eight- by 10-foot box, the 38-year-old onetime boxer sat as still as a statue with his head propped on his fist, eyes down on the defense table.

He didn't move as Purpura talked about his father's death, or when he showed jurors the funeral notice that Savage got in prison alerting him that his 9-year-old daughter had been killed by an errant bullet during a 2009 gang shootout.

Savage didn't testify during his three-month trial, and there are no signs that he intends to plead for his life. Still, the odds might be in his favor.

Federal prosecutors in Philadelphia have brought capital cases a half-dozen times in the last two decades, and none has ended with a defendant getting the death penalty.

Troyer said the punishment is reserved only for the most heinous crimes and the worst offenders.

"This is that case," he told jurors. "Kaboni Savage is that offender."

The hearing, he said, will include references to testimony and evidence that jurors heard during the trial. But some information will be new and highlight a key pillar of the government's argument: that Savage would remain a danger to society even if locked away for life.

Savage ordered seven murders from prison, Troyer noted, including the October 2004 firebombing that killed Marcella Coleman and Damir Jenkins, the mother and 15-month-old son of an FBI cooperating witness, Eugene Coleman, as well as four others.

And while he was supposed to be in restrictive federal custody, Savage found a way to make months of undetected personal calls on a line reserved for legal calls as recently as last fall, the prosecutor said. He also told friends how to doctor their letters to make them appear as if they were from his lawyer and thus would not be scrutinized by prison officials.

FBI agent Kevin Lewis, the lead case investigator, told jurors that Savage boasted to a prison guard that he "got a lot of information out on those calls and got a lot done."

Prosecutors also repeated for jurors some of the choicest quotes Savage was heard to say in prison, vowing to use all of his energy to kill his enemies, and their mothers and children. "Prison is not, I submit, a place where all of society is free from Kaboni Savage's wrath," Troyer said.

But the hearing will also shed light on Savage's life outside crime and give jurors "the whole picture of Kaboni Savage," his lawyer said.

Purpura said he will call witnesses to show the Savage family lost its guiding force and livelihood when Savage's father died of lung cancer. At age 13, Savage suddenly became the man of the house, succumbed to the violence and drugs that ringed their Hunting Park neighborhood, and found a mentor in drug trafficker Gerald Thomas.

Jurors will hear from or about Savage's four children and his nephew, a college student whom Savage has encouraged to lead a positive and law-abiding life, Purpura said.

"I've done enough negativity for all of us," Savage wrote the young man.

The lawyer said he will also ask jurors to compare Savage's fate to that of Lamont Lewis, the hit man hired by Savage to carry out the Coleman firebombing and other murders. In return for cooperating with prosecutors, Lewis is facing a prison term of 40 years to life.

After voting on the sentence, jurors will begin an identical hearing for Savage's codefendant, Steven Northington, convicted in two of the murders.

The other two defendants in the case, Robert Merritt Jr. and Savage's younger sister, Kidada, face up to life in prison when they are sentenced on conspiracy charges this year.

Contact John P. Martin at 215-925-2649, at jmartin@phillynews.com or @JPMartinInky on Twitter.