McNamee arrived at the U.S. Attorney's office in Washington accompanied by his lawyers, Richard Emery and Earl Ward. Asked by a reporter if he wanted to comment on the way into the building, McNamee shook his head no.
He has told federal agents and baseball investigator George Mitchell he injected Clemens more than a dozen times with steroids and human growth hormone from 1998-01. Clemens repeatedly has denied using illegal performance-enhancing drugs - including under oath.
McNamee was likely in town to prepare for his expected testimony before a grand jury that has been asked to determine whether Clemens should be indicted on charges of lying to Congress. A day earlier, and only a few blocks away, convicted steroids dealer Kirk Radomski appeared at the federal courthouse where that grand jury is seated.
A former New York Mets' clubhouse attendant, Radomski has admitted to selling speed, steroids and HGH to dozens of players from 1995 until Dec. 14, 2005. And it was Radomski who led federal investigators to McNamee.
They figure be among the primary witnesses against Clemens.
McNamee, once close friends with the former baseball star, has turned over to government agents syringes, vials and other items his lawyers said would link Clemens to drug use. Clemens' camp has called it "manufactured" evidence.
McNamee repeated his allegations under oath to congressional investigators and at a public House hearing in February - and Clemens testified in the same settings that he did not use performance-enhancers.
"I have never taken steroids or HGH," the pitcher said under oath.
Two former teammates of Clemens, Andy Pettitte and Chuck Knoblauch, both acknowledged to Congress that McNamee was correct when he said they used performance-enhancers.
Clemens' denials in sworn testimony prompted Congress to ask the Justice Department to look into whether Clemens lied, and the case was brought before a grand jury after an 11-month FBI inquiry.
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