BOSTON (AP) — James "Whitey" Bulger "deserves no mercy" and should be sentenced to two consecutive life prison terms, plus five years, for a string of murders and extortions, federal prosecutors told a judge in court papers filed Thursday.

"Bulger is one of the most violent and despicable criminals in Boston history. Having now been convicted of 31 felonies … Bulger richly deserves to spend the rest of his life in jail," prosecutors wrote in a sentencing memo.

They also asked the judge to order Bulger to pay restitution to the families of 19 murder victims, even though the jury at his trial convicted him in only 11 of the killings.

Bulger's lawyers, J.W. Carney Jr. and Hank Brennan, have not yet made their sentencing recommendation. They did not immediately return calls seeking comment on prosecutors' request. A two-day sentencing hearing is set to begin Wednesday in U.S. District Court.

Bulger, the 84-year-old former leader of the notorious Winter Hill Gang, was convicted in August after spending more than 16 years on the run. During the two-month trial, prosecutors portrayed him as a ruthless, hands-on crime boss who planned or ordered some of the murders and committed others himself.

In their sentencing memo, prosecutors said Bulger has "no redeeming qualities" and there are "no mitigating factors" to argue for a sentence less than life.

"Whitey Bulger's decades-long crime spree is now over," prosecutors wrote.

"Presiding over a massive criminal enterprise, Bulger extorted dozens of individuals, flooded South Boston with cocaine, shot innocent people, strangled women, murdered his competitors, corrupted FBI agents, and then ran away and hid for 16 years when he was finally indicted," they wrote. "While many of the victims will speak for themselves and their loved ones at the time of sentencing, the actual sentence should speak for itself: life in prison."

Bulger's "horrific crimes and sadistic behavior … demonstrate that he deserves no mercy at the time of sentencing," prosecutors wrote.

During the trial, Bulger's lawyers strongly denied a claim by prosecutors and Bulger's former partner that he was a longtime FBI informant who ratted on the Italian Mafia and other crime groups.

Bulger did not testify. In response to questions from the judge, he called the trial a "sham" and said he decided not to testify because the judge had prohibited him from presenting a defense using his claim that he had received immunity for his crimes decades ago from a now-deceased federal prosecutor.

Join our Newsletter for the latest news right to your inbox