Savage's "guiding philosophy" was clear, Gallagher said: Punish not just betrayers, but their mothers and children, too.
"Kids count to me," Savage told a cellmate on one of dozens of jailhouse recordings secretly compiled by the FBI and played during the three-month trial. "I'm killing what they love."
Gallagher's presentation launched what could be three days or more of closing arguments in the case against Savage.
Authorities have called Savage one of the most ruthless drug kingpins in city history, and say the firebombing was an unrivaled example of witness retaliation. If convicted, he and two codefendants could face the death penalty. The third codefendant, Savage's sister, Kidada, faces life in prison, having allegedly helped plan the bombing.
Savage's court-appointed lawyers are expected to urge jurors not to be swayed by his jailhouse rantings or the testimony of the government's star witness, who confessed to 11 murders and testified under a deal to spare him from the death penalty.
But Monday belonged to prosecutors. During a summation that lasted nearly six hours - and will resume Tuesday - Gallagher outlined Savage's role overseeing a vast and violent network that the lawyer said flooded North Philadelphia corners with drugs and relied on beatings, shootings, and killings to silence competitors or others who threatened the operation.
"They created a climate of fear, and in that climate, the defendants were able to thrive," Gallagher told the jurors.
Savage chose not to testify, but jurors have heard hours of his voice. Gallagher replayed portions of his testimony from a 2005 drug-trafficking trial and snippets from the jailhouse conversations in which Savage crows about "rats" and killing them.
The killings he is accused of carrying out or ordering include the execution-style shootings of five drug dealers, men who Savage allegedly believed posed a threat to his business or his freedom. Yet another killing was the 1998 shooting of Kenneth Lassiter near Eighth and Butler Streets after Lassiter accidentally bumped into Savage's car while both were trying to park.
Gallagher said the accident amounted to "less than a fender bender," but asserted that Savage had a deeper motive for killing Lassiter, a man he had never met. At the time, the drug trade on the block was controlled by Tybius Flowers, one of Savage's competitors. The shooting would draw police and hurt Flowers' business.
"Nothing heats up a drug corner like a murder," Gallagher said.
Later, Savage had Flowers killed, too, the prosecutor said.
But the centerpiece of the case is the firebombing that killed the mother, son, and four other relatives of Eugene "Twin" Coleman, a top lieutenant to Savage, after Coleman agreed to cooperate in the FBI investigation against Savage.
Gallagher told jurors that the fate of the Coleman family had been sealed before Coleman became a government witness. He said Savage and three of his associates had long before made "a pact" to kill the mother of anyone who cooperated against them.
One of the men at that meeting was Lamont Lewis, who later became the government's star witness. Lewis told jurors that he and another defendant, Robert Merritt Jr., doused the Coleman house with gasoline that 2004 night and lit the blaze while the family slept.
The home, instead of a safe place, became "a tomb for the Coleman family," Gallagher said.
U.S. District Judge R. Barclay Surrick told jurors they might begin deliberations later this week.
Contact John P. Martin at 215-925-2649, at firstname.lastname@example.org or @JPMartinInky on Twitter.