SAN FRANCISCO -- Barry Bonds' former girlfriend said he told her about his use of steroids around 1999 and also testified he underwent several physical and personality changes linked to the drugs starting at that time.  Kimberly Bell, the government's star witness in Bonds' trial on charges of perjury and obstruction of justice, said baseball's all-time home run leader became increasingly aggressive, lost his hair, developed acne and suffered from impotence.  Those are among the common side effects of steroid abuse.  Her testimony, sometimes delivered through tears, was the most dramatic development Monday as the trial began its second week.  Prosecutors are trying to prove Bonds lied when he told a grand jury in December 2003 that he had never knowingly used steroids.  Bell, who said her relationship with Bonds lasted from 1994-2003, testified that he demanded to know her whereabouts at all times and threatened her with bodily harm.  "He was just increasingly aggressive, irritable, agitated, very impatient, almost violent,'' Bell said.  Asked by prosecutor Jeff Nedrow what Bonds would tell her, she replied, "That he would cut my head off and leave me in a ditch.''  She testified that Bonds made those threats more than once, and also said, "That he would cut off my breast implants because he paid for them."  Bell said Bonds first acknowledged his use of steroids to her when she asked about a big lump in his injured elbow between 1999 and 2000.  "He said it was because of steroids, because somehow it caused the muscle and the tendons to grow faster than the joint could handle and it sort of blew out,'' Bell said.  Soon after that, Bell said, she noticed his physical changes.  "It's clear his overall body grew dramatically. Hair was falling out quickly and he ended up shaving his head. Changes in him sexually with his testicles and things like that. … The shape, size of his testicles, smaller and a different shape. And he had trouble keeping an erection. He tried different things to solve the problem. He had never experienced that before.''  Bell also said she saw Bonds and his former trainer, Greg Anderson, go into a room together and lock the door several times during spring training. She did not ask them what they were doing.  The government charges that Anderson, who pleaded guilty to distributing steroids in 2005, provided and administered the drugs to Bonds.  During cross-examination, defense attorney Cristina Arguedas questioned Bell about going on several radio shows and telling her story to the news media repeatedly.  Defense attorney Cristina Arguedas' cross-examination, which took up most of the court day, focused on the financial benefits Bell derived or attempted to extract from her relationship with Bonds.  In most of the morning session and part of the afternoon, Arguedas presented Bell as motivated to sell a book she was collaborating on with author Aphrodite Jones about her relationship with Bonds. Bell held firm to her contention that it was Jones, with whom she clashed until they ended their partnership, who was pushing to get publicity for the project.  Arguedas also projected Bell as becoming a resentful "road girlfriend'' after Bonds married the former Liz Watson in January 1998, but still willing to enjoy his largess.  Besides giving her between $60,000-80,000 for the down payment on a house in Scottsdale, Ariz., Bell said Bonds paid for her dental work and bought her cars.  Earlier in the proceedings, longtime Giants equipment manager Mike Murphy testified that Bonds' hat size changed from 7 ¼ to 7 3/8 around 2002, the year after he set the single-season home run record with 73.  Cranial growth past maturity has been linked with use of human growth hormone.  Murphy also testified that the hat size of two other Giants greats, Willie Mays and Willie McCovey, had also changed, but after they had gained weight while in retirement.  See photos of: Barry Bonds
Barry Bonds trial: Ex-girlfriend talks of aggression, steroids, impotence - Daily Pitch: MLB News, Standings, Schedules & More - USATODAY.com