Blood samples taken from the clothing and backpack of Dirk Greineder match the genetic profile of the Boston allergist's slain wife, a DNA expert testified in the doctor's murder trial Wednesday.

The testimony from the expert, Robin Cotton, director of the Cellmark Diagnostics genetics lab and one of the prosecution's most important witnesses against Dirk Greineder, did not, however, contradict the 60-year-old Greineder's story. The prominent doctor and teacher at Harvard Medical School says he discovered his wife's body, tried to help her and got her blood all over himself in the process.

Employing a dizzying array of charts and figures, the prominent DNA expert, who also testified during the O.J. Simpson trial, confidently explained how her laboratory went about comparing crime scene evidence with samples taken from individuals.

"Could a lot of other people have shared those characteristics (found in a sample), or are these characteristics so uncommon that not a lot of others could have? That's the question we're asking," she told the jury.

On the morning of October 31, 1999, Mabel Greineder, 58, was murdered while on a walk with her husband in a placid park in the affluent suburb of Wellesley.

The prosecution claims that Greineder hatched "an elaborate plan gone awry" to kill his wife in order to more freely pursue a secret life marked by obsession with pornography and trysts with call girls. Greineder says he separated from his wife momentarily on the path that day and returned to find her dead. The defense is arguing that she may have been the victim of a serial killer who had struck before in the region.

At the beginning of the trial, prosecutor Richard Grundy promised the jury that Cotton would give damning testimony against Greineder — that a sample lifted from a bloody glove found with the murder weapons near the crime scene would match the doctor's DNA.

But jurors expecting the prosecutor to make good on his promise will most likely have to wait until tomorrow, as Judge Paul Chernoff adjourned court before the scientist had a chance to discuss samples from the glove or the pocketknife and small hammer allegedly used in the murder.

Massachusetts State Trooper Martin Foley testified in the morning about the cleanliness of Greineder's hands in the aftermath of the killing, a point the prosecution has emphasized.

Grundy claims that the doctor's clean hands, in light of the blood stains which coated the rest of his body, are a dead giveaway — that he wore gloves during the killing and then discarded them.

To further the point, the prosecutor repeatedly asked Foley to tell the jury about Greineder's claim to have touched his wife's neck, slashed by the killer.

"He said he checked the carotid artery," Foley said, lifting his chin and holding his fingers up to his own neck to demonstrate.

Foley said that he found it strange that while Greineder claimed to have checked for a pulse on the neck twice — once upon discovering the body and once upon returning to the scene with authorities — the doctor didn't see the wound on the first occasion.

"He said he ran up to his wife's body (the second time) and checked her carotid artery on the left side and that was the first time that he saw the wound," the officer recalled.

Foley testified that the doctor also told him precisely what he did upon discovering his wife's body — actions the prosecution says would have soiled his hands.

"He told me he tried to pick her up. He said he couldn't pick her up," the trooper testified. "She weighed 120 pounds and he used to be able to left 250 pounds and he couldn't lift her. She was like a dead weight."

The clean hands stood out to Foley in the aftermath of the murder, and on the stand the trooper recalled his initial reaction.

"I asked him if he had washed his hands. He indicated no. Then I asked him if he had gone to the pond to wash his hands and he indicated no," Foley stated.

While the prosecution has harped on Greineder's hands throughout the trial, the defense has brushed aside the import of the evidence, saying that it was impossible to tell whether the doctor's hands were bloody because of police negligence.

"You never asked the defendant to stay (at the police station) so his hands could be tested for the presence of blood," defense attorney Martin Murphy asked incredulously during cross examination.

"No, I didn't," Foley admitted.

The testimony of Cotton resumes tomorrow at 9 a.m.

The trial is being broadcast on Court TV.