Known as Jimmy to his dwindling list of friends, Whitey to the rest of the world, he is at the center of a sordid tale of crime and corruption.
His lawyer has already acknowledged his criminal ways, saying he made "millions upon millions upon millions of dollars" from his life of crime, but says Bulger acted under a grant of immunity given by a former federal prosecutor.
At the age of 83, and facing a federal government hungry for a conviction on charges he murdered 19, he would seem to have little to lose at trial, making his expected testimony one of the most highly-anticipated courtroom events in memory.