Barry Bonds leaves the federal courthouse Tuesday. (Marcio Jose Sanchez / AP)

Updated at 1:38 p.m.

Steve Hoskins, a government witness in the perjury trial of home-run king Barry Bonds, testified that Bonds ordered him to research the effects of a steroid in 1999.

Hoskins, a childhood friend who later had a falling-out with Bonds over business matters, testified, according to the Associated Press, that he was more of a go-fer for Bonds, running errands, paying bills and taking equipment to the ballpark for him.

He testified that Bonds asked him to research the steroid Winstrol, asking what it was and what its effects were. Hoskins said that Bonds complained to him that his butt was sore from getting steroid injections.

Filed at 9:41 a.m.

The perjury trial of Barry Bonds resumes today at a federal courthouse in San Francisco with Jeff Novitsky, the lead investigator in the government’s probe of sports doping, returning to the stand.

Novitsky was unflappable Tuesday under questioning by Bonds’ attorney, Allen Ruby, whose cross-examination had only begun.

An earlier witness, Bonds’ former trainer Greg Anderson, refused to testify, was found in contempt of court and ordered by Judge Susan Illston to be held in custody for the duration of the trial. Anderson has already spent more than a year in jail for his refusal to testify; this is the fourth time in five years that he has been jailed for contempt of court.

Handicapping the trial, Mark Purdy, a San Jose Mercury News columnist, writes that the government’s most vital witness may be Stan Conte, the San Francisco Giants’ former trainer. Conte is more credible than two other government witnesses: Kim Bell, Bonds’ former mistress, and Steve Hoskins, a former business partner of Bonds’. Purdy writes:

[Conte] has no business beef with Bonds. He has not posed nude anywhere or profited from writing exposés. He left the Giants to work for the Los Angeles Dodgers in 2006 and has continued to build a reputation for being a standup guy -- as is proved by passages in the Mitchell Report, the official Major League Baseball investigative report on performance-enhancing drugs.

According to the report, during a 2002 road trip by the Giants, an "unidentified player" asked Conte about anabolic steroids. The player said he was thinking about obtaining the drugs from Anderson and wanted Conte's opinion. Conte tried to nuke the player's plan by describing the health hazards of steroids. Subsequently, Conte expressed concerns about Anderson to Giants officials, who essentially did nothing.

Also in the report: In 2003 -- the same year as Bonds' grand jury testimony -- Conte was interviewed by a federal law enforcement official about the Giants' steroid usage. Conte sadly told the official that "the horse had already left the barn."

Hmmmmm. A jury would be inclined to believe a guy like that. If the government has any chance to win the case, Conte's words will be its best weapon. Just a hunch.