(CNN) -- The longtime companion of notorious fugitive James "Whitey" Bulger agreed to plead guilty to several charges against her related to her infamous 16-year run from authorities with her alleged mobster boyfriend.
Catherine Greig will plead guilty to the charges of conspiracy and two counts of identity theft, according to court documents.
Greig will not have to testify against Bulger at his upcoming trial, CNN affiliate WCVB reported.
"In early 1995, I agreed to join Bulger and travel with Bulger during his flight from law enforcement. From January 1995 through June 22. 2011, I also agreed with others, including Bulger, to harbor and conceal him from law enforcement," Greig said in court documents.
Bulger, 82, has previously pleaded not guilty to all charges against him, including 19 murder charges.
Bulger, who is being held without bail, was the head of a South Boston Irish gang before he fled an impending racketeering indictment in 1995. He evaded law enforcement for 16 years before he and Greig were arrested in June 2011 in Santa Monica.
The couple had, for several years, hid in plain sight in this palm tree-lined, oceanside city near Los Angeles in a three-story building named Princess Eugenia.
Bulger was arrested after he was lured out of his apartment with an FBI ruse: He received a phone call and was told his lock box had been broken into in the basement parking lot area of his apartment building. When Bulger went down to check it out, FBI agents arrested him.
Neighbors said the couple was quiet. A manager of a restaurant near their home recalled how the alleged gangster and his girlfriend liked the privacy of a far corner table and once worked up a $192 bill, plus tip, for a steak and lobster dinner, accompanied by foie gras, vodka highballs and chardonnay.
But before settling into anonymity, Bulger was once one of the FBI's Top 10 most wanted fugitives. His alleged barbarity as an Irish-American mobster in Boston inspired the Jack Nicholson character in Martin Scorsese's 2006 film "The Departed."
Dick Lehr, who wrote a book about Bulger, described him as a cold-blooded killer whose gang went to lengths to avoid detection.
"When they killed someone -- this is pre-DNA -- they pulled the teeth out, cut the fingers off, tried to make it so the victims, if they were discovered from their graves, couldn't be identified. There's just no bottom. It doesn't get much uglier than someone like Whitey Bulger," Lehr said.
The FBI employed many methods to capture Bulger, including offering a $2 million reward. In 2011, the agency began airing a 30-second public service announcement aimed at getting Bulger. The agency bought about 350 ad spots in 14 U.S. cities.
The ad focused on Greig, then 60, and targeted female viewers around the same age. It described her as loving dogs and other animals and frequenting beauty salons. It said she had worked as a dental hygienist, likes to maintain her teeth, and had had multiple plastic surgeries.
Bulger's brother, William Bulger, is a former president of the University of Massachusetts and a state Senate leader. He was forced to step down from his university job after then-Gov. Mitt Romney, now a Republican presidential candidate, accused him of being evasive during congressional testimony about the whereabouts of his brother.
Greig could face a five-year sentence for each count, according to court documents.
For more on this story, go to CNN affiliate WCVB.