The longtime girlfriend of former Boston mob boss James "Whitey" Bulger is expected to plead guilty on Wednesday to contempt of court charges for refusing to testify whether anyone helped the couple during their 16 years on the run.

Catherine Greig, 64, pleaded guilty in 2012 to charges of identity fraud and harboring a fugitive during her long years in hiding with Bulger, who fled Boston in 1994 after a corrupt FBI agent warned him that arrest was imminent.

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She was sentenced to serve eight years in federal prison for those crimes and could face additional prison time for contempt. Federal law sets no maximum sentence for that charge.

Bulger, 86, was found guilty in 2013 of murdering or ordering the killings of 11 people while he ruled Boston's underworld as the notorious leader of the "Winter Hill" crime gang in the 1970s and 80s.

His run atop the FBI's "Ten Most Wanted List" ended in 2011 when agents arrested the pair at their California apartment building.

Bulger's 2013 trial highlighted his dealings with the FBI's Boston office, where fellow Irish-American agents turned a blind eye to Bulger's crimes in exchange for information they could use against the Italian-American mafia, then a top FBI target.

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The film "Black Mass," released last year and starring Johnny Depp as Bulger, told the story of the gangster's rise to power and ultimate flight from the city. Bulger's relationship with an earlier girlfriend is depicted in the film, but Greig did not appear as a character.

Greig's twin sister, Margaret McCusker, has criticized the contempt prosecution, contending she was serving a long enough sentence.