Bulger, as evidenced in his letters, now frames his legal predicament in grandiose, literary terms. While his enemies, including his former criminal confederates, might see him as the embodiment of Gypo Nolan, the treacherous protagonist in Liam O’Flaherty’s classic tale of betrayal “The Informer,” Bulger casts himself as Philip Nolan, the altruistic protagonist in “The Man Without a Country,” Edward Everett Hale’s short story. Nolan, a US Army officer, renounces his citizenship during his trial for treason and is sentenced to spend the rest of his life at sea, cut off from others. Bulger sees his isolation in high-security detention as he awaits trial in similarly epic terms, punishment for someone who knows too much about his government’s dark side.

The letters also suggest that Bulger is obsessed with refuting the charges that he strangled Debra Davis in 1981 and Deborah Hussey in 1985 before secretly burying their bodies. It is a point of honor for him; sorting out the truth will come down to his word against that of two former criminal associates.

Sunday, 81, who served time with Bulger in both the Atlanta federal penitentiary and the infamous Alcatraz in the 1950s and 1960s, remains sympathetic to the gangster. He said Bulger admits to some crimes, but says former associates who cut deals with the government while he was on the run have blamed him for other crimes he didn’t commit.

“I think Jimmy figures, okay this is the end and I want the truth out there,” Sunday said during an interview at his home in a Pittsburgh suburb. “I don’t think he wants to leave this world or spend the rest of whatever time he has left in it being falsely accused. . . . He wants his day in court.”

Bulger insists that the FBI didn’t use him, he used the FBI, and that he never helped the agency send anyone to jail. Bulger’s attorney, J.W. Carney Jr., has said Bulger alleges that a former federal prosecutor, Jeremiah O’Sullivan, who is now deceased, promised him lifetime immunity for his crimes — including murder.

Bulger told Sunday he refused to become an informer, despite regular beatings from police officers in his youth. But Bulger’s old court records tell a different story, showing that his first known cooperation with law enforcement was in 1956, when he agreed to identify his bank robbery accomplices so that his then-girlfriend would not face criminal charges for accompanying him on a trip that culminated with a bank robbery in Indiana. That early turn as a snitch was first reported by WBUR, citing documents obtained by two former Globe reporters, Gerard O’Neill and Dick Lehr, who also have a biography of Bulger coming out soon: “Whitey: The Life of America’s Most Notorious Crime Boss.”

The season of Whitey’s courtroom reckoning is also a season of new accounts of his life and misdeeds.

Bulger’s defiant insistence that he wasn’t an informant – directly refuted by sworn testimony, countless judicial findings, and extensive records showing that from 1975 to 1990 he was an informant for the now imprisoned former FBI agent John J. Connolly Jr.— seems to rest on semantics: Bulger claims his information was never used to put anyone in prison, so he can’t be considered an informant.

In his letters, Bulger said he looks forward to clearing his name at his upcoming trial, though he is also coldly realistic about his future: “Chances are I’ll die in this cell,” he wrote.

The letters from jail paint a portrait of Bulger as being deeply in love with Greig and regretting that he had met her a decade after he got out of prison in 1965 after serving nine years for bank robbery. He felt he could have left behind the criminal life he returned to shortly after his release.

“By the time we met it was too late,” he wrote. “I was in too deep, had done too much to even consider an honest way of life.”

Bulger describes his time on the run with Greig, where they posed as a retired couple, as the happiest of his life and like a 16-year honeymoon. “Became a real citizen and became a different person,” he wrote, “experienced emotions, feelings that I’d shut down for years.”