(CNN) -- A former CIA officer already serving a 23-year sentence for spying for the Russians may be facing even more time in prison.
Harold James "Jim" Nicholson is expected to change his plea to guilty at a federal court hearing in Portland, Oregon, Monday, according to court filings.
Nicholson pleaded guilty in 1997 to spying for Russia and is the highest-ranking CIA officer ever to be sentenced for espionage. While serving his prison sentence in Oregon, prosecutors allege, Nicholson, now 59, restarted his career as a double agent and enlisted his son Nathan in his efforts to collect money owed to him by the Russian spy services and to sell more secrets.
Both father and son were charged in January, 2009, with acting as agents of a foreign government, money laundering and conspiracy to commit money laundering.
According to the indictment, Jim Nicholson passed his son notes in prison and instructed him how to reinitiate contact with his old spymasters.
Nathan Nicholson made trips to California, Mexico, Peru and Cyprus, where he met with Russian government representatives who gave him payments totaling over $35,000 in cash, according to the indictment.
At his father's request, Nathan Nicholson allegedly shared the money with his sister and grandparents. Nathan Nicholson had complained to his father that he and his sister were short of money to pay for college, prosecutors said. Jim Nicholson told his son that his alleged spying activities "were 'risky' but not 'illegal,'" the indictment said.
An attorney for Jim Nicholson did not return CNNšs calls Friday.
According to court testimony, Nathan Nicholson, who is a former U.S. Army paratrooper, initially told authorities that he had traveled overseas to visit "a battle buddy." FBI agents informed Nicholson that lying to them was a federal crime and offered him a "mulligan," or a chance to change his story, according to the agent's testimony. At that point, FBI Special Agent John Cooney testified, Nicholson became more "forthcoming" about his meetings with Russians.
Nathan Nicholson pleaded guilty to his role in the intrigue last year but has not been sentenced. He was expected to have testified against his father at trial.
Prosecutors claimed some of the intelligence Nicholson was selling to the Russians was information on how he was captured. But Nicholsonšs defense team countered the Russians were already provided that information by Robert Hanssen, the FBI Special Agent convicted in 2001 of also spying for the Russians. Nicholsonšs defense team were seeking access to government debriefings of Hanssen following his arrest.
In court filings, the elder Nicholson appeared ready to fight the new charges and threatened to use his knowledge of the inner workings of U.S. intelligence against the government.
"At my trial I will possibly have to give some insight in my defense that could make things get a bit hot in D.C.," Nicholson wrote to his daughter in a September, 2010, letter that is part of the court record. "Some organizations may get burned," he wrote. "I donšt understand why they would want to bring that upon themselves just to exact petty vengeance on me."
Monday was supposed to have been the first day of Nicholson's trial. Instead he is expected to plead guilty and could face an additional 20 years in prison.