Filed at 11:54 a.m.; updated at 3:04 p.m.

The second week of Barry Bonds’ perjury trial began with Bonds’ former mistress and the San Francisco Giants’ former equipment manager testifying today as the trial enters an “ew” phase in a federal courthouse in San Francisco.

Last week, jurors heard experts’ graphic testimony about the physical changes that steroid use brings. This morning, Kimberly Bell, who had a nearly nine-year relationship with Bonds, testified about changes in his physique and demeanor.

She testified that, at one point, he had “a big lump ... [that] looked awful” in his elbow. Bonds told her that steroid use caused the muscle and tendons to outgrow the joint. “It blew out,” she said. She also said that Bonds talked about the widespread use of steroids among baseball players. “He mentioned that other players do it and that’s how they got ahead, that’s how they achieved,” Bell said.

Bell testified to changes in Bonds’ physical condition, saying that his sexual performance declined and that his testicles shrank. He developed acne on his back and grew (and shaved) chest hair, according to Bell.

“He was increasingly aggressive, irritable, agitated and very impatient,” she said. He began verbally abusing her, Bell testified, in 1999 and threatened “to cut my head off and leave me in a ditch.” She also testified that he threatened to “cut out my breast implants because he paid for them.”

On cross-examination, Cristina Arguedas pressed Bell on her assertion that she’d made a few media appearances, asking, “More than 20?” Arguedas then questioned Bell about whether she’d ever cried during any of her appearances and Bell said that she had gotten a “little emotional” at times.

Earlier in the day, Mike Murphy, a Giants’ employee for over 30 years, described changes in Bonds’ physique during the years in which he allegedly used performance-enhancing drugs. Murphy testified that Bonds wore a size 7 1/4 cap in 1993; by 2002, he wore a 7 3/8.