Lawyers for Barry Bonds' personal trainer say he'd rather go back to prison for a third time than take part in the grand jury investigation of his childhood friend for tax evasion and perjury.

Fresh off a 15-day jail term for refusing to cooperate in an earlier phase of the probe, Greg Anderson is expected to be called Thursday before a new grand jury investigating the San Francisco Giants slugger. But the trainer is expected to renew his vow of silence.

"He's resigned to do whatever it takes to maintain his integrity," said Paula Canny, an attorney and close friend of Anderson.

Anderson was released from prison last week on the same day prosecutors announced a grand jury investigating Bonds had expired without issuing an indictment. The new grand jury quickly was assembled, and Anderson received what was believed to be the first subpoena — ordering him to appear before the panel on Thursday.

If he again refuses to testify, he'll be hauled in front of a federal judge who will demand to know why he should be excused from testifying to a grand jury, a requirement even the president of the United States has to honor.

Since Anderson's legal arguments remain largely the same, the judge likely will send the trainer back to prison. It would be his third trip to a federal lockup in less than a year; Anderson served three months after pleading guilty to steroid distribution and money laundering stemming from the government's investigation of the Bay Area lab that allegedly supplied Bonds and other elite athletes with performance-enhancing drugs.

Authorities are investigating whether Bonds lied under oath when he told an earlier grand jury he didn't know whether the substances given to him by Anderson were steroids. The probe also reportedly is focused on whether Bonds paid taxes on the sale of hundreds of thousands of dollars worth of sports memorabilia.

Bonds' attorney, Michael Rains, says his client is guilty of nothing more than being famous.

"They're harassing Greg Anderson to get to Barry," Rains said.

Some legal experts see Anderson as the key to proving the perjury allegations, since Bonds reportedly testified the trainer gave him two substances that fit the description of "the cream" and "the clear" — two performance-enhancing drugs linked to the Bay Area Laboratory Co-Operative.

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 when federal agents raided Anderson's house, according to court papers connected to the steroids probe.

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 over the course of the four-year investigation. Chronicle reporters Lance Williams and Mark Fainaru-Wada have written a book based largely on leaked testimony.

"The gross, callous and destructive breaches of grand jury secrecy in this case create ample just cause for Mr. Anderson's refusal to testify," said one of Anderson's attorneys, Mark Geragos.

His 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 in the investigation.

"The government is violating the terms of the plea bargain," Canny said.

Anderson also claims he should not have to testify because he was the target of an illegal wiretap.

The new grand jury ordering Anderson's testimony can stay in session for as long as 18 months. By law, an intransigent Anderson can be locked up for the grand jury's full term, though a judge can free him sooner if convinced Anderson never will talk.