Authorities are investigating whether there are more victims in a spree that may have lasted 15 years or more.
They're also seeking the public's help in identifying a woman photographed with the alleged murderer -- a woman they believe may be a victim of Michael Gargiulo.
One victim Gargiulo is accused of slaying is fashion student Ashley Ellerin.
As Early Show national correspondent Hattie Kauffman reported Wednesday, Ellerin dated Hollywood stars, including Kutcher.
On Grammys night in 2001, Kutcher came by a bungalow to take Ellerin to a party. He knocked on the door, but there was no answer. So, Kauffman says, he went around to the back where, Kutcher later told police, he saw what looked like red wine stains on the carpet, then left.
Ellerin was found stabbed to death.
In 2005, just 40 miles away, another young woman, Maria Bruno, was killed in a similar manner -- a stabbing so vicious it shocked police.
"I've been a murder cop almost 18 years," says Det. Mark Lillienfeld of the Los Angeles Sheriff's Homicide Bureau, "and it's the most violent murder I ever saw, bar none."
There was, Kauffman points out, a pattern: women stabbed late at night, alone in their homes, with no apparent motive.
Last year, in Santa Monica, Calif., Kauffman continued, a woman was stabbed, but managed to fight back. DNA from blood at the scene led to the arrest of Gargiulo, and tied him to another murder, in Chicago, 15 years ago. Gargiulo was a high school classmate of Tricia Pacaccio.
Detectives connected the dots. Gargiulo lived near Ellerin, and was a neighbor of Bruno.
"He was associated with, or knew, or lived by, or had some contact with all of these women," says Lillienfeld.
Police say they've nabbed a serial killer.
But Gargiulo's former attorney says -- not so fast. "There's nothing physical that in any way substantially links him to any of these crimes," asserts Anthony Salerno. "It's simply a matter of the fact that he lived nearby and knew them."
Lillienfeld begs to differ, telling Kauffman, "In fact, there's an overwhelming amount of evidence, and some of the cases (are) more overwhelming (than) others. All of the cases, I think, are strong cases."
And on The Early Show Wednesday, he explained to co-anchor Harry Smith that there may at least one additional victim.
But investigators have no idea who the woman is.
"We believe the photograph(s) (were) taken in Southern California, probably in 2001 or 2002. ... (They) look like they were taken in a park or some kind of outdoor setting. But ... we have been unable, at this point in time, to identify who this woman is."
Lillienfeld says investigators have no leads. "We've actually shown the photograph to probably 100, 200 people that were associates or friends or relatives of both Mr. Gargiulo and people in his family and his work associates, and we've been unable to identify who this woman is," Lillienfeld told Smith.
"At first," he added, "we thought it was perhaps not something as nefarious as it appears now, but because we're having so much difficulty identifying her, and the fact that she appears physically very, very similar to those he is charged with murdering or attempting to murder, they all kind of have the same look...," police fear she fits the pattern.
He asked anyone knowing who the woman might be to call Los Angeles detectives at (323) 890-5500. "That would ... really help us out," Lillienfeld said. "We're hoping, certainly, that this woman is fine and that the pictures are kind of a fluke. As you can tell or the viewers can tell, looking at them as they progress, she appears more and more uncomfortable with Mr. Gargiulo as the photos are being taken. And it may be something very innocent, and then again, it may not be."