SAN FRANCISCO (AP) — Barry Bonds' trial was a lot like high school chemistry and biology class Thursday.
After former Bonds business partner Steve Hoskins finished a cross-examination in which he admitted his previous statements included inconsistencies and inaccuracies, Larry Bowers of the U.S. Anti-Doping Agency took the witness stand for more than four hours of mind-numbing testimony on the whats, whys and hows of steroids, human growth hormone and changes they cause to the body.
Bonds is charged with lying when he told a grand jury in 2003 that he didn't knowingly use performance-enhancing drugs. The jury of eight women and four men was treated to an Advanced Placement class in Androgen receptors and Acromegaly, a condition in which there is too much HGH in the body.
Prosecutors allege Bonds' feet, hands and head grew due to use of HGH, and Bowers testified as an expert witness about scientific studies alleging HGH abuse causes soft tissue swelling. Defense lawyer Allen Ruby tried to make the science sound like mumbo-jumbo.
"If someone abuses human growth hormone, how much does their head grow?" Ruby said. "Does it grow twice as big?"
Many of the times Ruby asked a pointed question, Bowers answered that there were too many variables to give a single answer.
"You know the difference between theories and proof?" Ruby asked sarcastically.
Bonds, in a dark suit, light pink shirt and dark pink tie, read through a binder book at his defense table. Jurors attentively followed, but they didn't take as many notes as they did during the testimony of Hoskins on Wednesday and Thursday morning.
The trial hasn't exactly been must-see drama in the Bay Area, where Bonds set major league season (73) and career (762) records for home runs during a career than ended in 2007.
When Bowers began his afternoon testimony, just 27 of the approximately 100 seats in the court room were occupied, and eight of those were in the Bonds family row. Having experienced the uncomfortable wood bench earlier in the week, three people in that row brought pillows with them.
Only three witnesses testified during the trial's first week, and there is no session on Fridays. When the trial resumes Monday, the government intends to call IRS Special Agent Mike Wilson, Bonds' former girlfriend Kimberly Bell, former Giants head athletic trainer Stan Conte and former Bonds personal shopper Kathy Hoskins.
Bowers, USADA's chief science officer, described how the organization helped unmask the designer steroid dubbed "the clear," which turned out to be Tetrahydrogestrinone (THG). Bonds admitted taking "the clear," but told the grand jury that personal trainer Greg Anderson — who is in prison for refusing to testify — informed him it was "flaxseed oil."
Bowers also testified about side effects of steroids use, such an acne breakout and "bloating." Looking ahead to Bell's expected testimony, Assistant U.S. Attorney Jeffrey D. Nedrow asked Bowers what effect steroid abuse could have on testicles.
"They would shrink," Bowers said.
Ruby confronted Bowers with the claim that any of the theories he espoused were "just speculation."
Out of the presence of the jury, U.S. District Judge Susan Illston denied Ruby's motion to exclude evidence on Acromegaly. Ruby claimed there was insufficient scientific evidence to allow the evidence.
Hoskins, his answers halting at times when he was confronted with inconsistencies, testified Wednesday that he suspected Bonds was using steroids from 1999-03, the year he was fired as Bonds' business partner. Hoskins also testified that Bonds' shoe and hat size grew — he had been in charge of ordering Bonds' spikes and keeping his uniforms in order.
During cross-examination Thursday, Hoskins admitted that he paid about $10,000 in legal fees for Bell, which she repaid after she sold her house. He also couldn't recall precisely the allegations his sister made against Bonds that he passed on to federal investigators.
At one point under questioning from Ruby, Hoskins appeared to get confused over which of Bonds' Bentleys they were talking about.
"He had so many cars, I don't remember," Hoskins said.

(Photo: AP Photo/Paul Sakuma)