Boston mob boss James "Whitey" Bulger has been jailed for two life terms plus five years for his role in gangland crimes, including 11 murders.

The 84-year-old former head of the Boston's infamous Winter Hill Gang remained stoic as a federal judge imposed punishment for what she branded "heinous" crimes.

Bulger was convicted in August in a broad indictment that included murder and racketeering charges dating back to the 1970s and 1980s.

The sentencing ends a sordid chapter in Boston history, marred by allegations of FBI and government corruption that allowed Bulger to continue his reign of terror for decades.

The South Boston gangster fled the city in 1994 and remained a fugitive until his capture in Santa Monica, California, in 2011.

Prior to handing down Bulger's sentence, Judge Denise Casper said the depravity of his crimes was "almost unfathomable", calling them "heinous" and "all about money".

Bulger showed no emotion as the judge spoke.

On Wednesday, the former gang leader mostly stared at the defence table as at least a dozen family members of Bulger's victims confronted him in court. Among them was Sean McGonagle, the son of Bulger victim Paul McGonagle.

He called the mobster "Satan", a "domestic terrorist" and a "sad, lonely and irrelevant old man".

Bulger, who declined to testify during what he called a "sham" trial, also refused the opportunity to address the court on Wednesday.

He branded the trial a sham after the judge denied his request to pursue an immunity defence. Bulger claimed a now-deceased federal prosecutor gave him immunity to commit crimes.