When Tricia Pacaccio was stabbed to death on her Glenview doorstep after an evening out with friends in August of 1993, it left the community devastated. She was 18 years old.

Seventeen years later, a lead suspect in the case— Michael Gargiulo— has not been prosecuted, 48 Hours Mystery correspondent Maureen Maher told Patch.

“Illinois detectives had several suspects early on, but little did they know their biggest break in the case would emerge after nearly 15 years and two other murders—one victim linked to Ashton Kutcher,” 48 Hours Mystery reported.

The story in a nutshell: Three women brutally stabbed, one alleged serial killer and a local family looking for answers.

Tonight, 48 Hours Mystery will air “The Boy Next Door,” a look at the connections between the Pacaccio murder and the murders of two young women in California.

The Pacaccio family has very rarely talked to the press outside of an initial “Inside Edition” interview following the murder, Maher said. Because the case was still under investigation, police asked the family not to share their story publically. Now, they’re looking for answers from the Cook County State's Attorney's office.

“[They want to know] the reason Cook County has not—and will not— prosecute the Pacaccio case, despite the DNA match,” Maher said, referring to the DNA evidence connecting Gargiulo to the Pacaccio crime scene.

When Tricia's brother Doug spoke to the "Early Show" May 13, he expressed the family's frustration.

"We've had the hardest time figuring out why this is happening the way it's happening," Pacaccio said. "They have DNA at the scene. ... So, why they haven't pursued this, to me, being on the inside, it seems somewhat political.

They would maybe have to admit that some mistakes were made and reconcile those mistakes, and at times I think, when political careers are involved, it's easier to ignore something that isn't close to them than to actually do the right thing and pursue it."

As authorities in California and Illinois have worked to piece together the three cases, evidence was found to link all the crimes to Gargiulo, 48 Hours reported in a recent release.

Even so, DNA evidence remains minimal leaving the victims’ families and friends to ask if Gargiulo will be convicted of murder, Maher said.

“…It certainly was frightening to hear that at least three different police departments believe Gargiulo may have been involved with or committed another 10 to 14 murders across this country and three to five in Mexico,” Maher said. “Tricia’s parents have been waiting a long, long time for answers—and some action. At a minimum, they deserve that."

Tune in tonight at 9 p.m. as CBS News’ 48 Hours Mystery investigates. Click here for a sneak peek. During the broadcast correspondent Maureen Maher and producers Doug Longhini and Josh Gelman will be available on Facebook to answer questions and respond to comments.