"The government didn't choose them, Bulger chose them," Wyshak said.
"The only thing worse than making a deal with (former hit man) John Martorano would have been not making a deal with John Martorano." Wyshak said the government "held its nose and made the deal."
It took prosecutors 90 minutes to detail the 19 murders Bulger is accused of, showing photos of each of the victims and the crime scenes.
Bulger is not charged with delivering the fatal blow in all of the murders, but is charged with participating as part of a racketeering conspiracy. Wyshak called Bulger "the leader of a very wide-ranging, broad organization," who is culpable for his co-conspirator's crimes.
But Wyshak made clear Bulger was the alleged triggerman in some cases, recalling testimony from Bulger's partner, Steve "The Rifleman" Flemmi, about the murder of John McIntyre, whose remains were exhumed from a shallow makeshift grave in 2000.
McIntyre had begun cooperating with the government on the shipment of weapons to the Irish Republican Army and 36 tons of marijuana imported into Boston Harbor.
"It's Arthur Barrett all over again, held at gunpoint, chained to the kitchen chair, interrogated," Wyshak said.
Flemmi said he was holding McIntyre's body while Bulger was trying to strangle him with a rope, but the rope was too thick.
After that didn't work, McIntyre practically begged for a bullet after Bulger asked him "would you like one in the head," according to Flemmi.
Wyshak got choked up at some points, trying to make Bulger appear utterly heartless.
In talking about the murder of Paul McGonagle, Wyshak recalls that Bulger's former cohorts testified that whenever they passed the Neponset River, where McGonagle's remains were exhumed in 2000, Bulger said, "'Drink up, Paulie.' That's the level of humanity that this defendant is operating at. ... And every time he goes by there its 'Drink up, Paulie.'"
Bulger was a fugitive for more than 16 years, after a crooked FBI agent told him in December 1994 he was about to be indicted on federal racketeering charges. The FBI track him down and arrested him 2011 in Santa Monica, California, where he had been living with his girlfriend under an alias.
During the trial, jurors heard dramatic testimony from convicted gangsters, bookies, extortion victims, a disgraced FBI supervisor, ex-drug-dealers, retired FBI agents and relatives of people Bulger is accused of killing.
Prosecutors called 63 witnesses. The defense called 10. Martorano testified for both sides, making a total of 72 witnesses over 35 days.
Bulger never took the stand despite repeated hints from his lawyers throughout trial he would testify. In fact, Bulger seemed to want to testify. Questioned by Judge Denise Casper, Bulger called his decision a "choice made involuntarily."
He claimed he had been given immunity for his crimes by the former head of New England's Organized-Crime Strike Force, Jeremiah O'Sullivan, now deceased.
"The evidence is overwhelming," Wyshak said as he concluded his closing argument.
He called Bulger "the leader of one of the most ruthless criminal organizations ever in Boston," one that "wreaked havoc on this city for decades."
"In his capacity as the leader, he is legally responsible for it all, as either a principle an aider and abettor or conspirator."
'Bulger: I didn't get a fair trial'
Bulger, who lost his temper several times during the trial, appeared angry, shaking his finger at the judge and claiming he was "choked off from making an adequate defense."
"I didn't get a fair trial. This is a sham. Do what ya's want with me," Bulger said.
Families of the victims have been in court every day of the trial. The wife of one of the victims shouted "You're a coward!"
Patricia Donahue's husband, a truck driver, was killed in the crossfire of a slaying Bulger allegedly committed. She later explained Bulger had a chance to take the stand and tell the truth.
Flemmi testified as one of the government's star witnesses, and he said that he saw Bulger strangle the two women. The defense team, however, presented evidence that Flemmi had the greater motive to kill the women -- his girlfriend and his stepdaughter.