Pacaccio was found stabbed to death in the driveway of her family's north suburban home back in 1993. A man California police call "The Hollywood Ripper" is charged with her murder.
Pacaccio was an 18-year-old Glenbrook South graduate. She was popular, an "A" student. A week before she was to leave to go to school at Purdue, Pacaccio was brutally stabbed to death at the door of her home. There was no evidence of sexual assault, robbery, or motive.
Cook County Sheriff's investigators early on considered 17-year-old Michael Gargiulo -- who lived a block away from Pacaccio in unincorporated Glenview -- as a possible suspect, but they didn't have a case.
Gargiulo moved to California. In 2003, investigators obtained DNA from Gargiulo, and it matched DNA found on Pacaccio's fingernails after the murder. But no charges were filed.
Three years ago, Gargiulo was arrested and charged with two murders in Los Angeles: The 2001 stabbing death of Ashley Ellerin, a one-time girlfriend of actor Ashton Kutcher, the 2005 stabbing death of Maria Bruno, and an attempted murder in Santa Monica in 2008.
Two months ago, the CBS program "48 Hours Mystery" reported on a likely link between Gargiulo and the unsolved slaying of Tricia Pacaccio. After that program aired, two former L.A. friends of Gargiulo came forward to say that he told them years ago that he had murdered a woman in Chicago.
"It was these additional third party admissions, combined with the existing evidence we had gathered in this case, that enabled us to move forward with these charges," said Cook County State's Attorney Anita Alvarez.
Gargiulo is now formally charged with Tricia Pacaccio's murder.
Pacaccio's parents were not available for comment Thursday, but they have long been angry with the state's attorney's office for not pursuing charges based on the DNA match back in 2003.
The state's attorney Thursday said the fingernail DNA link eight years ago was not strong enough to support a murder case.
"The DNA that was recovered in 2003 was a mixture, and it was, according to the experts, something that could not exclude casual contact," Alvarez said
In this month's edition of Chicago Magazine, Bryan Smith tells of the agonies lived by Pacaccio's parents, and their belief that prosecutors dropped the ball years ago.
"They say he should have been charged right then, and that is what they are really furious about," Smith said.
In a statement to Chicago Magazine, Pacaccio's mother said: "My husband and I both feel that what Cook COunty did is, once they found DNA, instead of pursuing [the suspect] Michael [Gargiulo], they made false excuses on why DNA was on her. How pathetic."
Alvarez defended the progress of the investigation Thursday.
"That DNA standing alone based on the evidence that we had was not sufficient to bring charges," said Alvarez.
The former L.A. friends of Gargiulo who have come forward say, although they dismissed his claim as a killer when they first heard it, they saw it quite differently after the detailed television report on the Pacaccio murder.
The state's attorney and the sheriff both said Thursday their departments never gave up on the investigation, though the Pacaccio's have a different take, at least in terms of what county prosecutors did.
Gargiulo will eventually be brought back to Illinois for trial, but the California cases will go first. That process is not supposed to start until 2012. Los Angeles detectives say Gargiulo is a suspect in as many as ten murders, but he has denied any involvement in the California killings or that of Pacaccio.