James "Whitey" Bulger Update: Prosecutors want proof alleged mobster had immunity deal with feds

Whitey Bulger's long-awaited trial is finally slated to begin.
Whitey Bulger
James "Whitey" Bulger
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(CBS/AP) BOSTON - James "Whitey" Bulger is being asked for proof that in the 1970s federal authorities gave him immunity for his alleged role in 19 slayings. 

Pictures: Guns and Money: Whitey Bulger evidence

Bulger, an 83-year-old alleged former mobster, is expected to go on trial for the killings in June. His defense team has demanded that the judge compel the government to turn over "all correspondence" between prosecutors and investigative agencies, the Boston Herald reports.

Prosecutors do not believe Bulger's claim of immunity, calling it "frivolous" and "absurd," in documents filed Friday. They say Bulger's FBI file does not mention any deal between the defendant and former U.S. Attorney Jeremiah O'Sullivan in the 1970s.

Furthermore, the prosecution claims Bulger has produced no proof he ever met O'Sullivan.

Prosecutors say Bulger's upcoming trial will transform into an "unduly elongated and unmanageable" mess without proof of the alleged immunity deal.

Complete coverage of "Whitey" Bulger on Crimesider