File photo shows Kimberly Bell leaving federal court in San...

File photo shows Kimberly Bell leaving federal court in San Francisco. (March 17, 2006) Credit: AP

SAN FRANCISCO -- In testimony both tearful and confrontational, Barry Bonds' former mistress Monday described the advent of his hair loss, acne and other changes to the anatomy that a doping expert previously said could be caused by the use of anabolic steroids.

Kimberly Bell said she was Bonds' girlfriend from 1994 until 2003, when he told her "to disappear.'' She also testified that the former slugger threatened her more than once, insisting, "I thought he would kill me.''

Bell, who said she met Bonds in the parking lot at Candlestick Park after a game during his playing career for the Giants, is a prosecution witness in the case against Bonds. He is accused of four counts of perjury and one of obstructing justice for allegedly lying to a federal grand jury.

In testimony, Bell described Bonds' shrinking body parts and behavior in which he became "aggressive, irritable and impatient'' from 1999 to 2001.

Twice during the long session, Bell began to sob. On other occasions, she was terse with a defense attorney.

Bonds, 46, sat next to his attorneys, occasionally twisting in his chair and taking notes but not showing any emotion.

Bell said that Bonds, after they broke up, refused to pay for a Scottsdale, Ariz., home he had promised her.

When asked by prosecutor Jeff Nedrow if she ever discussed steroids with Bonds, Bell responded that she did around 1999-2000 at her apartment in Mountain View, Calif., about 30 miles south of San Francisco. Bonds had a serious elbow injury, and Bell had asked why it was so severe, and, she testified, "He said it was because of steroids.''

She said he told her that Mark McGwire and other ballplayers were using steroids "to get ahead.'' McGwire in 1998 set the single-season home run record of 70, which Bonds broke with 73 in 2001.

Defense attorney Chris Arguedas tried to poke holes in Bell's testimony by insisting Bell was only trying to make money off her relationship with Bonds, by authoring a book with a ghost writer.

Bell was depicted as a bitter former girlfriend who in trying to promote the book, which never was completed, went on various radio and television programs, including Howard Stern's.

Arguedas also made much of the fact that when Bell signed the lease for the Scottsdale house, where she lived from 2002-04, it was as a "secondary home,'' not a primary home, trying to persuade the jury Bell committed fraud on the documents.

Bell said she first thought of Bonds as the actor Richard Gere in the film "An Officer and a Gentleman,'' but was hurt when he told her in 1998 he was marrying someone else.

Longtime Giants equipment manager Mike Murphy, who conceded he was "very nervous,'' said Bonds originally wore a size 71/4 baseball cap but that his head size increased to 73/8. Murphy also explained, however, that the hat sizes of Giants Hall of Famers Willie Mays and Willie McCovey also increased as they aged, although it occurred after their playing careers ended.

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