DEDHAM, Mass. — During brisk but heated opening statements, lawyers argued about whether Dirk Greineder's obsession with pornography and prostitutes led the renowned doctor to murder his wife of 32 years.

"On the surface, he was demanding, no-nonsense, soft-spoken ... but he was a man of secrets, deeply and closely held secrets," said lead prosecutor Richard Grundy of Greineder, 60, who ran up large phone sex bills, frequented Internet pornography sites, and often had trysts with call girls under the alias "Thomas Young."

Defense lawyer Martin Murphy acknowledged his client's infidelity but dismissed it as irrelevant, claiming that authorities grasped onto his moral shortcomings to bolster a weak case.

"This is not a case about whether Dirk Greineder is guilty of infidelity ... This is not a case of whether Dirk Greineder committed adultery," the lawyer said in a measured but forceful tone, standing barely three feet from the jury box. "All of [this] has nothing to do with the murder of May Greineder. [It] has everything to do with the prosecution's desperate search to find a motive to explain why Dirk Greineder killed her."

Greineder kept a poker face during both opening statements, watching each lawyer attentively and slightly slouching into a wooden chair behind the defense table. Occasionally, when his children or family life was mentioned, the doctor turned his head and made eye contact with his daughter Britt, 28, sitting just behind him on a courtroom bench. Although the two other Greineder children, Kristen, 30, and Colin, 25, studiously ignored their father, all three have declared their belief in his innocence.

The prosecution says Dirk Greineder killed Mabel "May" Greineder, 58, so that he could more freely pursue his secret sexual life. Describing the doctor's actions as "an elaborate plan gone awry," Grundy says he invited his wife out for a walk in a serene suburban park on the morning of Oct. 31, 1999, so he could bludgeon her over the head and cut her throat on an isolated wooded path.

But Murphy said the murder was the work of an unknown killer and dismissed the idea that his client hatched a plan to kill his own wife. He claimed that the couple, frequent visitors to the park area, were simply following "the plan that they always have" — to walk their dog and get some exercise.

The lawyer told the jurors that the Greineders split up after Mabel hurt her back descending a ridge on the way to the area where the couple generally played fetch with their dog. The doctor continued on and left his wife behind, Murphy said, and never again saw her alive.

The lawyers gave jurors a preview of the dizzying amount of physical evidence they will see presented during the trial. At the center of case are two sets of gloves — one worn by Mabel Greineder, the other sodden with her blood and discarded by her assailant after the murder.

Grundy told the jury that tests conducted on two gloves recovered from nearby sewer drains showed both the DNA of Greineder and the blood of his wife.

"These gloves will be connected to the defendant in at least six ways," the prosecutor said. He claimed that, in addition to both gloves bearing Greineder's DNA, both were found hidden near places the doctor was seen after the murder, and that the pair was only available in the Boston area at a store named Diehl's where he frequently shopped.

In a search of the Greineder home conducted several days after the murder, police found an identical pair of gloves in the backyard doghouse, the prosecutor added.

But Murphy had his own set of gloves to tell the jury about, those worn by the victim. While the right hand glove was found lying near the crime scene, the other was still on Mabel Greineder's left hand when cops found her body. A stranger's DNA was found on this second glove.

Holding a report from the lab to which the prosecution sent the glove for tests, the lawyer read, "The DNA obtained from this sample also contains types which could not have originated from either Mabel Greineder or Dirk Greineder."

He told the jury that this unknown DNA sample was evidence of an anonymous killer scenario, one which authorities did not thoroughly pursue in their haste to pin the crime on his client. "Who is that stranger?" Murphy asked. "The answer is we don't know. We don't know because police and prosecutors did not conduct a fair and objective search for the truth."

The lawyer repeatedly attacked the authorities' methods of solving and prosecuting the case to call into question the considerable evidence the prosecutor had promised to reveal to jurors.

The prosecutor said that two murder weapons — a small hammer and a pocket knife — were found in a sewer drain with one of the bloody gloves. Both had the victim's blood and Greineder's DNA on them, he claimed.

At the crime scene, numerous items were recovered that Grundy said pointed to a premeditated murder. Three one-gallon ziplock bags and one large garbage bag lay under a branch near the body. The prosecutor said tests matched the smaller bags to a box found at the Greineder home, and theorized that the doctor meant to use them to dispose of the murder evidence cleanly.

In addition, police found a baking pan containing an unopened packet of surgical gloves and a bottle of lighter fluid whose label advertised it as "excellent for removing stains" well buried underneath leaves near the crime scene. The prosecutor hypothesized that Greineder had planted the equipment to help in the murder and cover-up, but then had changed plans at the last moment and never unearthed it.

The prosecutor added that other evidence at the scene pointed to an attack that didn't go according to plan. Drag marks found at the crime scene indicated that the murderer pulled his victim about 10 feet into the woods after killing her. Grundy told jurors that heel marks found along the path where the body was dragged "have the same size as the defendant's heels and have some of the same manufacturer's characteristics."

Although the prosecutor enumerated this wealth of evidence, Murphy cautioned jurors that they would have to wait to evaluate the strength of each piece. "We'll have a chance to hold [the evidence] up to the light, to see whether it makes sense, to see whether it holds up," he promised.

Opening statements concluded around noon, but the prosecution could only put two minor witnesses on the stand before Judge Paul Chernoff cut the day of testimony short when one of the jurors developed a migraine headache.

Jason Harris, a paramedic, and Ken DeMerchant, a fireman, were two of the first people on the scene after authorities were alerted of the attack. Both described the gruesome sight of the body and noted that they saw Greineder talking with other emergency personnel, but neither added much insight into his emotional state at the time.

Judge Chernoff declared that he was "unwilling to dismiss [the] juror," perhaps because he had already removed another member of the panel late Wednesday after the juror discovered that a close friend was on the witness list.

Testimony resumes Friday morning at 9:00 a.m. ET. The trial is being broadcast live on Court TV.