Lance Armstrong’s legal journey took another spin this week, as anti-doping authorities said the fallen cycling star finally agreed to spill the beans under oath, while ABC News reported that Armstrong still faces charges of witness tampering and obstruction. Legal experts say if the latter charges are true, Armstrong is in big trouble.

“If he were convicted of obstruction of justice or witness tampering in the federal system, he would face jail time,” said Matthew Cannon, a former supervisory assistant U.S. Attorney for the Central District of Illinois. “But it’s pretty difficult to get that conviction. It is very fact-driven.”

During his seven years, Cannon convicted contractors who were bilking the U.S. government during the Iraq war. “We had a witness tampering conviction, but we had the whole meeting on tape,” said Cannon, who recently joined the Chicago firm of Greenberg Traurig, LLP.

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In February 2012, the U.S. Attorney in Los Angeles dropped a two-year probe against Armstrong, despite grand jury testimony by Armstrong’s former teammates and associates on the U.S. Postal Service cycling team. This week, sources told ABC News that another office of the Department of Justice was moving forward on charges that Armstrong bullied witnesses who were testifying against him. Obstruction of justice is the “frustration of governmental purposes by violence, corruption, destruction of evidence, or deceit,” according to the Congressional Research Service.

Former teammate Tyler Hamilton has said that Armstrong threatened him in an Aspen restaurant in 2011 before he testified about his role in doping. There have also been reports that Armstrong threatened the wives of two former teammates, one via text message. Still, Cannon says the bar is pretty high.

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“One person’s word is not going to be what prosecutors are going to indict somebody on,” Cannon said. “They are probably going to be looking for more than that.”

The feds have a mixed record in pursuing athlete/dopers.

• Pitcher Roger Clemens was acquitted in 2012 after two trials on perjury charges for lying about his use of steroids.
• Slugger Barry Bonds was convicted in 2011 of obstruction, but acquitted on three perjury charges of lying before a grand jury investigating steroids. He got probation.
• Track cyclist Tammy Thomas was convicted of felony perjury and obstruction of justice in 2008. She got probation.
• Olympic sprinter Marion Jones spent six months in jail on a perjury conviction in 2008 after lying about her use of performance-enhancing drugs to a federal grand jury.

Armstrong may face a similar legal path, even though the final outcome is still unclear.

“The bigger danger (for Armstrong) is the risk of perjury,” said Charles Pelkey, a defense attorney and cycling journalist based in Laramie, Wyo.

If Armstrong confesses under oath to the U.S. Anti-Doping Agency in order to reduce his lifetime cycling ban, and that contradicts his earlier statements to the federal government, he could face perjury charges, according to both Pelkey and Cannon.