DURHAM, N.C. — An agent with the State Bureau of Investigation was under fire on the witness stand by defense attorneys in day 30 of the Mike Peterson trial, claiming that his bloodstain analysis suggests that Kathleen Peterson was beaten to death in the stairwell.

Defense attorney David Rudolf started hammering away at SBI agent Peter Duane Deaver's testimony from the start of Tuesday's court session. For most of the day, Rudolf grilled the blood spatter expert about his seven experiments to re-create Kathleen Peterson's death.

During his experiments, Deaver used a styrofoam head with a blood-soaked sponge attached to it. He concluded that Kathleen Peterson was definitely beaten to death.

"How did you determine how much blood to use?" Rudolf asked.

"Basically, we wanted the sponge to have enough blood on it to be a source of blood, so there was no specific determination," Deaver said.

Deaver also tested Mike Peterson's clothes to try and determine how they got blood on them. Rudolf jumped in to suggest that Deaver's experiments were unscientific and unreliable.

"You understand good science involves not just confirming your own theory, but about disproving an alternative theory. You understand that, don't you?" Rudolf said.

"I do," Deaver said.

"And you didn't do that with the shorts, did you?" Rudolf asked.

"No, I did not," Deaver said.

Rudolf also questioned Deaver's theory, pointing out that a blowpoke, the weapon prosecutors claim Mike Peterson used to kill his wife, was 3.5 feet long and the stairwell was too narrow to use just a weapon.

Rudolf alluded to Dr. Henry Lee, the blood spatter expert for the defense. Lee, who is known for his work on the O.J. Simpson case, said his report shows the blood stains are inconsistent with a beating.

Deaver is expected to return to the stand Wednesday morning.