DURHAM, N.C. — A neuropathologist called in to consult on Kathleen Peterson's autopsy testified Tuesday that he determined she probably lay bleeding from her head for "several hours" before she died at the bottom of stairs in the home she shared with her husband.

Thomas Bouldin, a professor of pathology at the University of North Carolina School of Medicine, was the 49th witness called by prosecutors during the 38 days jurors have sat listening to evidence against novelist Michael Peterson.

Thomas Bouldin testified he believed Kathleen Peterson was alive for hours after her injury.

Bouldin's testimony bolstered the prosecution's contention that Michael Peterson spent a considerable amount of time trying to make his wife's death appear to be an accidental fall before calling 911 on Dec. 9, 2001. The defense contends that Kathleen Peterson slipped or collapsed in a dimly lit stairwell, struck her head, stood up, slipped in blood, and struck her head again.

The medical testimony was dry and riddled with scientific terminology, but jurors listened intently as Bouldin went through his findings. The jury of eight women and four men gave the same attention to the testimony of Aaron Gleckman, an associate medical examiner for the State of North Carolina.

Gleckman was brought in to consult in April on the autopsy of Elizabeth Ratliff, a 43-year-old neighbor of Peterson when he lived in Germany in 1985. Like Kathleen Peterson, Ratliff was found dead at the bottom of stairs and police initially believed her death an accidental fall.

A U.S. Army pathologist testified previously that he concluded after an autopsy that Ratliff suffered a brain hemorrhage, but Gleckman testified that his review of a second autopsy done this year found no evidence of that.

Gleckman also cast doubt on the initial findings, noting that the Army pathologist, Larry Barnes, noted blood in Ratliff's spinal column without having removed the spinal cord.

"So he was just in error when he wrote that in his report?" prosecutor Jim Hardin Jr. asked.

"Yes, he was in error. You can't see the cervical spinal canal without removing the spinal cord and sectioning it," Gleckman testified.

Then Hardin got to the heart of the matter for jurors.

"Do you have an opinion to the cause of death as it relates to Elizabeth Ratliff?" Hardin asked.

"Miss Ratliff died from blunt trauma to the head ... [It] was from a homicidal assault," Gleckman said.

The testimony could be damaging to Peterson. His lead lawyer, David Rudolf, has argued in motions and through his questions that the German and U.S. military authorities who investigated Ratliff's death in 1985 were in the best position to determine how she died.

Ratliff's body was originally autopsied by the U.S. Army because the school teacher was a civilian employee of the U.S. Department of Defense.

On cross-examination, Rudolf established that Gleckman had just 22 months' experience in the medical examiner's office and that his findings do not coincide with the prestigious Armed Forces Institute of Pathology  (AFIP). The AFIP's chief forensic pathologist reviewed the Army autopsy in 1986 and agreed that Ratliff probably died from a sudden brain hemorrhage.

"Well, that's what they concluded," Gleckman said, disagreeing with the finding.

"Did you find any evidence whatsoever that there was a spontaneous rupture in her brain?" Hardin, the prosecutor, asked.

"No, there's no evidence of that," Gleckman said.

Peterson, who faces life in prison if convicted, was stoic throughout the testimony. He came to court wearing a red carnation Tuesday but his lawyers said they did not know why he chose to wear the flower in his lapel.

Testimony resumes at 9:30 a.m. Wednesday. The trial is being broadcast by Court TV.