A federal judge ordered Barry Bonds' personal trainer to testify Thursday before a grand jury investigating whether the baseball star lied about using steroids.
If Greg Anderson refuses to testify, he will be sent back to prison for contempt of court.
Anderson, 40, has twice served time in less than a year in connection with a Bay Area-based performance-enhancing drug ring linked to some of the top athletes in the world, including Bonds, New York Yankees slugger Jason Giambi and sprinter Tim Montgomery.
Anderson has vowed to remain quiet.
If he continues to do so, he could be held until he either agrees to testify, or the grand jury's term expires in 17 months or Judge William Alsup becomes convinced that the divorced father will never break his vow of silence.
Anderson spent 15 days in prison last month for refusing to testify, but was freed after that grand jury's term expired.
He also served three months in prison and three months of home detention after pleading guilty to steroid distribution and money laundering stemming from the government's investigation of the Bay Area Laboratory Co-Operative (BALCO), which allegedly supplied Bonds and other athletes with performance-enhancing drugs.
Anderson has refused four times to testify before federal grand juries investigating Bonds.
Government lawyers are investigating whether Bonds lied under oath when he told an earlier grand jury he didn't know whether the substances Anderson gave him were steroids.
The grand jury probe also reportedly is focused on whether the San Francisco Giants slugger paid taxes on the sale of hundreds of thousands of dollars worth of sports memorabilia.
The New York Times reported last month that the grand jury is also probing the possible involvement of, the track coach of sprinters Marion Jones and Justin Gatlin. Gatlin, the 100-meter co-world record holder, tested positive earlier this year for elevated levels of testosterone.
Some legal experts see Anderson as the key to proving the perjury allegations, since Bonds reportedly testified that the trainer gave him two substances that fit the description of "the cream" and "the clear," two drugs linked to BALCO. In 2003, Bonds reportedly testified to the grand jury investigating BALCO that he believed the substances were flaxseed oil and arthritis balm, not steroids.
Anderson also could offer insight into the doping calendars bearing Bonds' name that were seized by federal agents from the trainer's house, according to court papers.
But Anderson's lawyers say he shouldn't have to testify because of the numerous leaks of secret grand jury testimony to the San Francisco Chronicle during the course of the four-year investigation. Chronicle reporters Lance Williams and Mark Fainaru-Wada have written a book based largely on testimony leaked by unnamed sources.
A different federal judge has told the reporters they must tell a grand jury who gave them the information. The pair have said they would go to jail rather than reveal their source or sources.
Anderson's lawyers also say the agreement he made with prosecutors to plead guilty last year in the BALCO case stipulated he wouldn't have to cooperate with investigators. Anderson also shouldn't have to testify because he was the target of an illegal wiretap, they argue.