McNamee put himself in Clemens' crosshairs when he signed a proffer agreement with federal prosecutors, stipulating that he could not be charged with steroid distribution as long as everything he told the prosecutors was truthful. He also was asked to cooperate with the baseball-commissioned steroids investigation led by former Sen. George Mitchell, which made public McNamee's claims that he injected Clemens with steroids and growth hormone in 1998, 2000 and 2001.
Congress decided to hold its hearing after Clemens publicly challenged the veracity of the Mitchell report.
Clemens filed a defamation lawsuit against McNamee last January. McNamee's attorneys have since argued to have the suit thrown out; and last month, they filed a defamation suit on McNamee's behalf against Clemens.
Clemens is the latest professional athlete to come under federal scrutiny for statements made about alleged use of steroids or performance-enhancing drugs. Last year, the FBI opened an investigation into whether Houston Astros shortstop Miguel Tejada lied in 2005 when, during a congressional follow-up on testimony given by Rafael Palmeiro, he told House committee staff that he never took steroids or HGH.
Barry Bonds, a seven-time MVP, was indicted last year on perjury and obstruction of justice charges stemming from his 2003 grand jury testimony in which he denied knowingly taking illegal performance-enhancing drugs. Bonds is scheduled for trial this March in San Francisco.
If an indictment is returned against Clemens, it could set the stage for high-profile perjury trials for a generation's top hitter and pitcher.
A retired FBI agent said that perjury cases involving high-profile defendants are becoming more common, telling ESPN.com, "It used to be we didn't mess with these kinds of cases. Everybody lied to us. Then, they got Martha Stewart on lying, and it became the flavor of the month."
The FBI began investigating Clemens last February, two weeks after the pitching icon and McNamee offered starkly conflicting testimony before a House committee hearing. Attorney General Michael Mukasey was initially asked to investigate Clemens by leadership of the House Oversight and Government Reform Committee. Lawmakers did not ask for a similar investigation of McNamee.
With his Hall of Fame candidacy potentially hanging in the balance, Clemens told the House committee, "I have never taken steroids or HGH. No matter what we discuss here today, I am never going to have my name restored."
Without looking at McNamee, who was seated next to him, Clemens told committee members, "I have strong disagreements with what this man says about me."
Just minutes earlier, McNamee told committee members, "When I told Sen. Mitchell that I injected Roger Clemens with performance-enhancing drugs, I told the truth. I told the truth about steroids and human growth hormone. I injected those drugs into the body of Roger Clemens at his direction. Unfortunately, Roger has denied this and has led a full-court attack on my credibility."