DURHAM, N.C. — He testified in the O.J. Simpson, Jon Benet Ramsey and Michael Skakel murder trials, and on Monday, renowned forensic scientist Henry Lee played professor to a rapt jury in Michael Peterson's wife-slay trial, telling them that 10,000 pieces of blood spatter can't be wrong.

"You have to look at the totality, you cannot just look at one isolated pattern," said Lee, contradicting a prosecution expert who said three "cast-off" blood spots suggest Kathleen Peterson was bludgeoned to death at the bottom of a set of stairs. "Things are not always simple and easy."

Novelist Michael Peterson has much to gain if Lee helps convince the jury in his Durham, N.C., trial that his wife's death was anything but simple.  The first witness called by his lawyers was a forensic neuropathologist who testified that Kathleen probably fell not once, but twice, in the steep stairwell, hitting her head on the stairs multiple times each fall.

Prosecutors say the simplest explanation for seven lacerations they count on the back of the victim's head is that Peterson, who could spend life in jail if convicted of first-degree murder, beat her to death.

The bloody stairway at the Peterson home

Lee augmented the neuropathologist's scenario with a his own vision of Kathleen Peterson writhing in agony before she died, diluting some of the blood evidence with urine, and coughing up blood to coat the lower portion of the stairwell wall.

The expert's testimony was highly anticipated, and jurors warmed up immediately to the affable witness, responding almost in unison to his chipper "hello" Monday morning as he took the witness stand.

But it was Lee's time off the stand, which he spent demonstrating principles and techniques of forensics for the jury, that appeared to build a rapport with them.  Lee, a professor at the University of New Haven, began with an impromptu version of Forensics 101. 

Enlisting the aid of defense lawyer David Rudolf, Lee squirted red ink from an eye-dropper onto white posterboard from a variety of angles and heights, demonstrating how many different types of blood spatter can be formed.

To show how spatter diameter changes with impact speed, Lee dropped ink from the eye dropper at three different hights.  To demonstrate impact spatter, he slammed his ink-soaked fist onto one board.  And to simulate cast-off spatter, he flicked the eye dropper at the board (hitting Rudolf in the process).

Forensic expert Henry Lee demonstrates blood spatter.

Lee maintains that much of the blood in the stairwell was aspirated, or coughed up by Kathleen Peterson. To demonstrate that pattern, he traded red ink for watered down ketchup, coughing up a spray of spatter that coated nearly the entire board.

If the jury wants to believe Kathleen Peterson really died from a fall, Lee's coughing example could explain the sheer volume of blood at the bottom of the stairwell.  And his cast-off demonstration could help jurors discount three groups of spatters found 9 feet up on a header above the stairwell floor. 

After cleaning a dollop of condiment from his upper lip, Lee attacked the claims of a key prosecution witness, North Carolina Bureau of Investigation agent Peter "Duane" Deaver.

Deaver performed a number of experiments to replicate the blood spatter that would be created by the state's theory.  Lee ridiculed Deaver's "so-called experiments," calling them "child's play" and picking them apart one by one.

On cross-examination, prosecutor James Hardin Jr. got Lee to admit that the conclusions that could be drawn from the blood spatter evidence were highly limited.  Lee had little to say about the lacerations, which remain one of the most damning pieces of evidence facing Peterson in this 12-week trial.

Hardin also asked Lee why he hadn't tested the supposed aspiration blood spatter for saliva.  "That's not my job.  If they do their job properly," said Lee testily, referring to the local officials, "I do not have to come here." 

Whether they believe his explanation of the spatter, there should be little question in jurors' minds of Lee's import to the field of forensic science. 

Lee, who said he'd visited more than a thousand death scenes and "more than hundreds" of beating death scenes, said Monday that he was slated to testify at the upcoming Texas murder trial of real-estate millionaire Robert Durst, former basketball star Jayson Williams' manslaughter trial, and "the other Peterson case," Scott Peterson's upcoming trial for the murder of his wife Laci.

After a half hour spent laying out Lee's credentials Rudolf approached his star witness and asked him to identify a 1-inch stack of papers fastened with a black alligator clip. 

"This is a copy of my resume, but it's a couple of years old," Lee deadpanned. "I did not have time to update it."

Lee, whose fingers, when he left the stand, still had the red tint of his ink, will continue under cross-examination Tuesday morning at 9:30 a.m. ET.

Peterson's trial is being broadcast by Court TV.