Flecks of Mabel Greineder's blood could have landed on Dirk Greineder's clothing after being kicked up from his shoes or from dripping off the victim's bloody hair, a blood stain expert testified for the defense on Friday in the Boston allergist's murder trial.

A type of blood stain known as "satellite" spatter, caused when drops of blood hit a flat surface and kick up smaller droplets, the expert testified, could explain the marks the prosecution says prove Greineder, 60, bludgeoned and stabbed his wife of 32 years to death in a park near their Wellesley, Mass. home on October 31, 1999. Prosecutors have tried to prove that the blood stains on the defendant's clothes came as he repeatedly struck his wife with a hammer.

Testimony from the expert, Stewart James, was the defense's second push in the past two days to refute ample physical evidence the prosecution says ties the doctor to the slaying. Yesterday, defense attorney Martin Murphy took aim at DNA evidence linking Greineder to a knife and pair of gloves used in the murder.

At the close of testimony Friday, Judge Paul Chernoff told the jury that he hopes to have the case in their hands by the end of Monday. Murphy has yet to call two of Greineder's children, Britt, 28, and Colin, 25. His oldest child, Kirsten, 30, testified Monday.

Greineder, who is charged with first-degree murder, says he briefly walked ahead of his wife, 58, during a stroll the morning she was bludgeoned and stabbed to death. His lawyers claim the police failed to consider the possibility of a serial killer, noting that two other people had been killed in nearby Massachusetts parks around the time Greineder's wife was slain.

The prosecution, however, claims Greineder needed his wife out of the way to continue his secret life of porn and prostitution.

Earlier in the week, Greineder told the jury how he reacted when he found his wife lying, slain, on the park path. He testified that he tried three times to pick her up, and could not recall whether her head contacted his shoulder, or any part of her chest contacted his chest. He said he used a "jerking motion" to try to pull her up, but only managed to lift the small-framed woman of average stature six inches off of the ground.

James, the blood stain expert, testified that without knowing exactly how Greineder tried to pick up his wife, it would be fruitless to speculate how the stains on his clothing were created.

James said that experts from the prosecution jumped to conclusions in labeling flecks of blood on Greineder's jacket, shoes, and pants "impact" stains — the kind of marks that are made when a blunt object strikes wet blood and sends small droplets into the air.

In a calm voice, James explained that "molecular cohesive forces" provide the surface tension to keep a droplet of blood together. He said that a phenomenon called "satellite" spatter could break this surface tension and scatter small droplets that resemble those made from impact spatter.

But satellite spatter, he said, could be caused by the regular falling of droplets of blood onto a flat surface or onto themselves.

"If one received a single blow to the head with a blunt object, the possibilities of spatter being produced are very very remote," James testified.

Greineder's blood-spattered sneakers

He pointed out three larger droplets on the tongue and lace of one of Greineder's shoes, a pair of white, Reebox jogging shoes, and noted that these larger stains were caused by drips of blood, not spatter, and could have contributed to satellite spatter.

James cautioned that satellite stains could be misinterpreted as impact spatter.

"Should satellite spatter be ruled out?" asked Murphy. "No," James replied.

James noted that drops could have been kicked up from landing on Greineder's shoes, or even on leaves next to his shoes. He also noted that drops of blood fallen from Mabel Greineder's bloody hair could have caused the marks on Greineder's clothing. The blood stains, James testified, were not necessarily caused by the doctor wielding a two-pound sledgehammer.

"I can't tell you what activities could have taken place in order to create the spatter," said James, when prosecutor Richard Grundy asked on cross-examination whether he could rule out impact spatter from causing the marks on Greineder's pants.

"Would it then be speculation?" asked Grundy.

"Yes," he replied, "and I just refuse to do that."

During cross-examination, Grundy challenged James over passages from the scientist's own forensics manual. He attacked James for writing that "the examination of the crime scene … is the single most important" thing for a forensic scientist to do, yet James had never visited Morse's Pond where Mabel Greineder was murdered.

James responded that the passage Grundy read was only meant to refer to preserved crime scenes, whereas he was asked to consult on this case more than a year after the murder took place.

The prosecutor also wondered how spatter could have made it to the upper parts of Greineder's body.

"I'm not certain … as to just exactly how Mabel Greineder was moved," James said. "It may be possible to have a spatter or two coming off a different portion of her."

Richard Belliveau, a private investigator who photographed areas of Morse's Pond for the defense and collected a variety of items of garbage to show that the area was frequented by people, testified briefly about the EZ loaf pan found in the forest.

If, as expected, Murphy calls Britt Greineder on Monday, the middle child of the family will have to address why she asked her father, "What happened to you and mom today?" in the police station after the killing. Greineder's son, Colin, is also expected to testify.

The trial, which is being broadcast by Court TV, will continue Monday at 8:30 a.m.