DEDHAM, Mass. (Court TV) — Thomas Young had not seen Dirk Greineder, his Yale University roommate, for 30 years when he got a telephone call in March 2000 from a Massachusetts State Police homicide detective.

Trooper Sgt. Martin Foley, who was investigating the murder of Greineder's wife, Mabel "May" Greineder, was reluctant to say much over the phone but suggested Young check out several stories on the Web sites of two Boston newspapers.

When the retired lawyer went online, he learned that his old friend, who became a renowned Boston area allergist, allegedly assumed the name "Thomas Young" in pursuit of his interest in online pornography, phone sex and trysts with women from escort services.

"I was distressed when I heard about it," the real Thomas Young, 60, told Court TV after testifying Tuesday afternoon at Kirk Greineder's murder trial.

Prosecutor Richard Grundy called Young and several other witnesses to the stand after the lunch break as he began trying to prove to the jury that Greineder killed his wife of 31 years to accommodate his secret lifestyle.

Mohan Jitlal, an American Express records custodian, testified that Greineder opened a credit account in his name in July 1998 and also authorized a "Thomas Young" to use the corporate card. The credit card was used by Greineder to pay for a hotel room in New Jersey a week before his wife was killed; the card was also used to pay for phone sex calls in Young's name about the same time.

The real Thomas Young testified that other than an occasional Christmas card, he had not seen or heard from Greineder since about 1970. Both men attended Yale from 1958 to 1962 and lived in the same suite with other students in their sophomore year at the prestigious Connecticut school.

Young went on to law school. Greineder became a doctor.

Outside the courthouse, Young recalled Greineder as a conscientious student and champion swimmer who was well-liked at Yale.

"I liked the guy. I had great admiration for him," Young said. "He was very studious. He was very disciplined and had a self-deprecating sense of humor that I found charming."

Greineder's lawyer, Martin Murphy, did not ask Young any questions. During his opening statement to the jury on May 24, Murphy said all the evidence about his client's double life is irrelevant to the question of how bludgeoned Mabel Greineder with a hammer and slashed her throat with a knife.

"All of [this] has nothing to do with the murder of May Greineder," Murphy said at the time. {It] has everything to do with the prosecution's desperate search to find a motive to explain why Dirk Greineder killed her ... He didn't do it."

Young, who noticed, along with courtroom observers, that Greineder did not look at him as he testified, declined comment when asked whether he felt it is fair for the prosecution to bring up the defendant's private sexual desires.

Testimony concluded at 3 p.m. Tuesday and will resume at 8:45 a.m. Judge Paul Chernoff indicated outside the presence of the jury that he will hold a hearing at 7:45 a.m. Wednesday before ruling on whether the identity of two witnesses yet to testify will be shielded in any way.

The prosecution's motion to shield the witnesses was sealed. It is believed that they are both women Greineder allegedly contacted for sex using the Thomas Young alias.

The trial is being broadcast by Court TV.