DURHAM, N.C. — Tiny specks of blood on the inside of novelist Michael Peterson's shorts suggest he was near the stairwell when his wife either fell or was beaten, based on the testimony of a blood stain analyst Thursday.

The testimony, which jurors in Peterson's murder trial will hear Monday, is potentially damaging for the defense because Peterson, 59, claimed he was outside alone smoking a cigarette when his wife of nearly five years apparently slipped or passed out, struck her head and bled to death.

North Carolina State Bureau of Investigation Agent Peter "Duane" Deaver offered his conclusions outside the presence of jurors so Judge Orlando Hudson Jr. could decide whether the science is sound. Hudson later agreed to allow the testimony, making the hearing merely a lengthy exercise from which the defense can get a preview of Deaver's findings.

Among other things, Deaver concluded:

• That Kathleen Peterson was assaulted in the stairwell by someone outside the stairwell wielding a blunt object. Deaver cited a "cast off" stain on a wall 9 feet above the floor outside the stairwell to support that finding;
  
  
• That the victim was struck at least three times and that her head may have struck the stairs when she fell more than once; 
  
  
• Michael Peterson had to be standing, crouching or sitting near a blood source — either his bleeding wife or a pool of her blood — when a great force was applied to the blood source. He concluded this by the location and size of eight tiny drops of blood found inside Peterson's shorts, on the right rear leg. When a small amount of force is applied, large drops, or spatter, is created. A large amount of force breaks blood up into small specks, he explained;
  
  
• There is evidence that someone smeared blood in a failed effort to clean it up;
  
  
• Marks in blood on two of the steps appeared to have been made by something like a fireplace poker. Police never found a poker in the house but believe Peterson or someone helping him got rid of one Kathleen Peterson's sister gave her as a gift about 15 years ago.

Defense lawyer David Rudolf cross-examined Deaver about his conclusions Friday morning and then argued unsuccessfully that they were flawed and should not come into evidence.

But Deaver's testimony during the hearing provided much fodder for the eventual cross-examination before the jury. The defense has already played a videotape of a test Deaver conducted using bloody mops and wigs to mock his methods and conclusions.

One conclusion that the defense will have to explain is Deaver's opinion that spatter patterns on the walls in the stairwell could have only been created when Kathleen Peterson's head was struck "in space" and not from hitting the floor or walls.

"I came up with points of impact which were in space. That means they were not on a surface," Deaver said.

The defense is expected to call its own experts later in the trial to say that the blood stain patterns are consistent with Kathleen Peterson falling, striking her head, lying prone, getting up, slipping in her own blood, and then striking her head again.

The trial is now in its eighth week and is being broadcast by Court TV.