An hour after his wife was murdered in a serene suburban park, Dirk Greineder asked authorities whether he could go home in order to take care of his dog, a state police trooper testified during the renowned Boston-area doctor's trial Tuesday.

Trooper Martin Foley said he denied the surprising request, but accompanied the doctor home later that day in October 1999. When they arrived at the suburban house, the officer recalled, Greineder didn't do anything special for the dog.

"He just put it outside," said Foley, a silver-haired man who chose to remain standing while testifying and kept his arms tightly clasped in front of him.

The 60-year-old Greineder, head of the allergy department and Brigham and Women's Hospital and a teacher at Harvard Medical School, asked to go home after explaining to Foley in considerable detail the circumstances surrounding his wife's killing on the morning of October 31.

Mabel Greineder was bludgeoned and stabbed while out on a walk with her husband. While authorities claim that he killed her in order to more freely live a secret sex life, the doctor maintains that the couple separated on their walk and an unknown assailant attacked her.

That was the story Greineder told Foley, the state trooper, shortly after the attack when police and other emergency personnel arrived on the scene.

"At some point his wife stumbled and had a twinge in her back," Foley testified. "He said May told him to continue on walking the dog so that the dog could go for a swim. They were to meet at the end of the access road on a rock."

In addition to chronicling the sequence of events that led up to the attack, Greineder also described the quiet morning that he says he shared with his wife before going on their walk.

"He woke up around six in the morning. He woke his wife up around seven to have breakfast. He said he prepared fresh fruit and muffins for his wife," Foley testified.

Because the victim's clothes were rumpled as if she had been a victim of a sexual assault, the officer said he also asked Greineder questions about the couple's sex life.

"He said that he and his wife weren't sexually active and hadn't been for a few years. He said that she had a bad back," the officer said.

When Foley searched the Greineder home in the days after the murder, he found evidence of the doctor's clandestine sexual activities.

Prosecutor Richard Grundy handed the officer a cardboard box discovered in the couple's garage and asked him about two items it contained.

"The first is a prescription for Viagra. The second is a twelve-pack of trojan condoms," the officer noted, pulling the evidence out of the box and holding it up for the jury.

Reading the pill bottle, the officer then testified that Greineder had prescribed Viagra for himself. It had been filled on June 12, 1999 with 12 pills, and several were missing when the evidence was seized five months later on November 12.

Another dramatic moment occurred when Grundy asked a series of questions about a newly acquired life insurance policy discovered by police in the Greineder home.

A seemingly endless string of objections from defense lawyer Martin Murphy kept Foley from testifying about the meaning or implications of the policy, and so eventually the documents were just given to the jury to examine themselves.

The life insurance pays $500,000 to the couple's three children, but only if both die, making it an unlikely motivation for the killing.

Testimony resumes Wednesday morning at 9 a.m.

The trial is being broadcast on Court TV.