John Albert Gardner III, 31, will be sentenced in San Diego Friday under a plea agreement that spares him the death penalty but denies him any possibility of parole.
It's likely to be a drama-packed session, since the parents of both teens were slated to address him at directly at the sentencing, reports CBS News Correspondent Ben Tracy.
Gardner's guilty plea last month to killing 14-year-old Amber Dubois and 17-year-old Chelsea King has sparked a far-reaching review of how California deals with sex predators, a campaign that advocates hope to take to Washington and other state capitals.
Calls to stiffen penalties for child sex offenders began almost the moment Gardner was arrested Feb. 28, three days after he attacked Chelsea on an afternoon run in San Diego, strangled her, and buried her in a shallow, lakeside grave.
Gardner served five years of a six-year prison sentence for beating and molesting a 13-year-old girl in San Diego in 2000. He faced a maximum of nearly 11 years in prison, but prosecutors called for six years.
A court-appointed psychiatrist urged the maximum sentence allowed by law. He said in court documents that Gardner was a "continued danger to underage girls" and "an extremely poor candidate" for treatment.
Maurice Dubois, Amber Dubois's father, says in his statement to be read Friday that psychiatrist Dr. Matthew Carroll "was the only one who saw Gardner for what he is, a dangerous predator interested in young girls."
In the statement, Dubois likens his daughter's killer to a mountain lion, whose instincts are to stalk and attack. If the zookeeper frees the lion from captivity, he asks, who is responsible for the killings that come after?
Dubois heaps blame on the criminal justice system.
"It's obvious the legal system failed us here, with all of the missed opportunities that ultimately allowed this monster to stalk our streets and harm our loved ones," Dubois writes in his statement, released Thursday in San Diego Superior Court.
Gardner not only confessed, heto CBS affiliate KFMB in San Diego about his crimes, remarking, "Do you think that I don't have guilt and I don't hate myself for what I did?? I was not in control."
But Amber's mother, Carrie McGonigle, isn't buying it, saying, "He could have gotten help and he could have come forward way sooner. And you know what? Chelsea may still be alive if he would have felt guilty."
The case has put California's parole system under the microscope.
Gardner lived little more than a football field's length from a San Diego preschool for at least 16 months while on parole from 2005 to 2008. That violated a condition of parole that prohibited him from living within a half-mile of a school.
A corrections department official let him stay until his lease expired in 2006 but no one noticed he was still living there until a year later. The parole board could have sent him back to prison but kept him on parole, where he had six other less serious potential violations.
Gov. Arnold Schwarzenegger has ordered a state board to review the parole system.
Brent and Kelly King, Chelsea's parents, are leading a campaign for "Chelsea's Law" to allow life sentences for some convicted child molesters in California and lifetime electronic monitoring of others. The bill, which cleared its first legislative committee last month, would also ban sex offenders from parks.
"I will channel my rage and commit to spending my life to making our society safe from the incurable evil," Brent King said at a memorial service in March. "Known sexual predators are not curable ... If anyone - anyone - believes that this evil is treatable, let them live next door to you and your children, not ours."
Chelsea was a straight-A student who ran on the cross-country team in suburban Poway, played French horn in a youth symphony and was active in her school's peer counseling program.
The discovery of Chelsea's semen-stained clothing during a massive search quickly led authorities to Gardner. Days later, he led investigators to Amber's remains in a remote, mountainous area north of San Diego.
The investigation into Amber's disappearance had gone nowhere since the Future Farmers of America member disappeared walking to school in suburban Escondido in February 2009.
Gardner led authorities to Amber's remains on condition that the information not be used in court. Investigators were unable to independently link him to the crime, and his guilty plea to that murder was a big reason the death penalty was dropped.
Gardner also pleaded guilty to attempting to rape a jogger on Dec. 27, near the spot where he attacked Chelsea.