"With the Barry Bonds trial likely to last several weeks, the 12 jurors who will decide if the home run king is a felon were probably hoping for some entertaining material, and they could do a lot worse than orchidometers.

Orchidometers, as the jury learned Thursday, are devices used to measure a man's testicles. And while there's no evidence an orchidometer was ever used on Bonds, prosecutors have made his testicle size a central feature of their case as they try to prove Bonds misled the BALCO grand jury in 2003.

Bonds' former mistress Kimberly Bell, who once posed for Playboy, was at the courthouse Thursday but won't testify until next week. She is expected to tell jurors that starting in 2000 she observed Bonds suffering from acne, bloating, hair loss and testicular shrinkage - all documented side effects of steroid abuse.

To create a scientific foundation for those observations, the government Thursday called to the witness stand Larry Bowers, the .science director for the U.S. Anti-Doping Agency."