DEDHAM, Mass. — Mabel "May" Greineder's underwear and bra were slashed when police discovered her dead body in a quiet suburban park, a police lab scientist who tested the clothing testified Thursday.

Dirk Greineder, who is being tried for first-degree murder in the killing, and the couple's three children all averted their eyes as Gwen Pino held the undergarments aloft on the stand and explained that cuts had been made in the left cup of the victim's black bra and down the front of her red underwear.

The victim, 58, was murdered while on a walk with her husband in the wooded Morse's Pond recreation area on the morning of October 31, 1999. The defense claims that the couple separated during their outing and that an unknown assailant — perhaps the same person who killed and sexually assaulted an elderly woman a year earlier in a park in a nearby town — bludgeoned Greineder over the head and cut her throat. An elderly man was found bludgeoned to death in another nearby town park in August 1999.

The judge has agreed to allow Greineder's defense attorney to pursue a so-called "serial killer" theory and question witnesses in a limited manner about the previous killings.

The prosecution, however, maintains that Greineder killed his wife so he could more freely pursue a secret life marked by an obsession with pornography and secret trysts with call girls. Calling the murder "an elaborate plan gone awry," lead prosecutor Richard Grundy hinted during opening statements that Greineder had tried to make the murder seem like the work of another man.

The bulk of the sixth day of testimony in the trial was proffered by a state police trooper specializing in foot ware analysis who told the jury that footprints consistent with Greineder's shoes were found at the crime scene.

Clearly no stranger to the witness stand, diminutive Sergeant Deborah Rebeiro methodically catalogued the lengthy list of different foot marks she discovered on the wooded park path where the murder occurred. The presentation included numerous photographs of the area that included the victim's body, gruesome sights that the Greineder family also studiously ignored.

Rebeiro told the jury about discovering five prints that matched characteristics from Greineder's shoes. One of those prints, she said, pointed in a direction consistent with someone standing in the position necessary to begin pulling the victim's body into the woods, as drag marks at the scene indicate occurred.

"The heel area of foot mark seven was located with the curved surface of the heel towards the victim," Rebeiro told the jury.

But no more marks were found along the route that the victim was dragged, and Greineder acknowledges twice being around the site of the murder — once when he says he discovered his wife's body and once when returning to the scene with a police officer.

Rebeiro dealt a small blow to the defense's theory of an unknown assailant when she testified that no foot marks were found that could not be matched with either Greineder or emergency personnel who walked through the scene.

Defense attorney Martin Murphy tried to show during cross-examination that few prints were made by anyone on the hardened earth of the park path and that a lack of foot marks did not preclude the presence of others at the scene.

"All you saw is one paw?" he asked her about a solitary dog print found near the body. "Is it fair to say, sergeant, that there aren't many one-pawed dogs?"

The long cross-examination, in which Rebeiro marked each print found on a large poster, didn't hold the attention of the jury very well.

"I'm looking for a breaking point for the jurors' morning recess," Judge Paul Chernoff told Murphy at one point.

"I'm sure they are too," the lawyer replied, eliciting a chorus of laughs from the panel.

Pino's testimony, mainly about blood samples taken from evidence found at or near the murder scene, took up the rest of the day.

But the scientist only analyzed whether each item was marked by human blood and did not test for blood type or DNA characteristics of the samples. Testing of this manner was conducted by a different lab. A representative from that laboratory is expected to take the stand next week.

Pino also told jurors about several items — a cellular phone, Greineder's steering wheel, and a door handle in a police car that he rode within in the aftermath of the killing — where no blood was discovered.

The prosecution claims that a lack of blood on the defendant's hands, in light of blood smears on the rest of his clothing, indicates that he wore gloves when killing his wife and then disposed of them.

Two bloody gloves were found discarded in storm drains in the park.

The trial is being broadcast on Court TV.