Mobster James 'Whitey' Bulger will spend the rest of his life behind bars, after his appeal to the U.S. Supreme Court was rejected.

The Irish American gangster had made a last-ditch bid to the highest court in the U.S. to overturn his 2013 conviction for participating in  11 murders, while running a sprawling Boston-based criminal empire from the 1970s to the 1990s.

His lawyers maintained that the 87-year-old was denied a fair trial because the judge prevented him from testifying that a now-dead former U.S. prosecutor game him immunity for his crimes in exchange for protection.

But on Monday the U.S. Supreme Court declined to hear his appeal, meaning the former gang leader will spend the rest of his life in jail. Bulger is serving a life sentence without the possibility of parole at a federal penitentiary in Florida.

In March this year he was also unsuccessful in an appeal to the federal appeals court, which upheld his convictions on 31 of 32 criminal counts he faced in his racketeering trial, including 11 murders, extortion and drug offenses.

Black Mass, a book on Bulger's rise to power and eventual flight, was turned into a 2015 movie starring Johnny Depp as the mobster.