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With reporters camped on the sidewalk and fans yelling from passing cars, San Francisco Giants slugger Barry Bonds testified Thursday before a federal grand jury looking into possible tax and drug violations by a California sports lab that supplied nutritional supplements to some of the nation’s top athletes

The spectacle of Bonds, widely considered the best player of his generation, appearing under subpoena marked the most dramatic moment in a months-long investigation.

He spent 5 1/2 hours inside the grand jury room, emerging at 4:25 p.m. and offering only brief comments.

Asked how it went, Bonds said: “Fine.” Asked if he was glad it was over, he said: “Yes.”

Bonds’ testimony, while yielding no new public information about the grand jury’s probe, contributed symbolic value.

This drama was set in motion in September when law-enforcement authorities raided a company called Bay Area Laboratory Co-Operative, or BALCO, in Burlingame, Calif.

The grand jury is trying to determine whether BALCO was the source of a new type of “designer steroid”–called tetrahydrogestrinone or THG–that appears to have been created for the purpose of helping cheaters avoid detection. The grand jury is also looking into the company’s finances.

BALCO owner Victor Conte has denied any wrongdoing.

Over the past month, some of BALCO’s best-known clients have been subpoenaed as witnesses to talk about what they purchased from the company. Some have reportedly been granted limited immunity in return for their testimony.

Olympic gold medalists Marion Jones and Tim Montgomery have appeared. So have numerous National Football League players. Bonds, however, was the most anticipated witness in the probe.

Television news trucks set up outside the courthouse Wednesday night. By early Thursday, about 30 reporters and photographers held vigil at the court entrance, the driveway to an underground parking garage and the foyer on the 17th floor where the grand jury meets.

A courthouse official had said Bonds would receive no special treatment, but shortly before 11 a.m. he was allowed to pull into underground parking that had been closed to other subpoenaed witnesses.

Bonds, who holds the record for most home runs in a season with 73, emerged from the elevator on the 17th floor smiling and wearing dark slacks and a gray jacket. Accompanied by a bodyguard and his attorney, Michael Rains, Bonds ignored requests for comment.

His teammate in recent seasons, Benito Santiago, subsequently entered the jury room to testify. Bonds’ mother and wife arrived and waited on a bench in the hallway.

The famed left fielder had come under particular scrutiny because he was a loyal BALCO client before the raids and because Greg Anderson, a personal trainer for Bonds and other athletes, is a target of the investigation.

Bonds has denied using steroids. Last month, Rains said Bonds would tell the grand jury that he grew more muscular late in his career through training and nutritional supplements.

While the media glare focused on Bonds, other developments in the effort to combat the use of banned substances played out quietly elsewhere.

The International Olympic Committee on Thursday authorized the retesting of samples collected during the 2002 Winter Games in Salt Lake City, and widened the scope of testing at next summer’s Athens Olympics.

A day earlier, American track and field officials had voted to recommend a lifetime ban for athletes caught using steroids.

Taken together, these developments prompted some experts to suggest that the anti-doping effort, which for many years has proceeded in fits and starts, is gaining momentum.

“This isn’t about any one individual on any particular day,” said Frank Shorter, the 1972 Olympic marathon gold medalist and longtime anti-doping activist. “A lot is happening and I think there has been a paradigm shift … the clean athlete has been empowered.”