Should they insist that prosecutors seek the death penalty against a man charged with raping and murdering their 17-year-old daughter? Or do they settle for life in prison in exchange for his plea of guilty to the murders of their child and a 14-year-old girl whose killing would have otherwise gone unresolved?

John Albert Gardner III pleaded guilty Friday to raping and murdering both Chelsea and Amber Dubois in a plea agreement that called for life in prison and he would reveal details about how they vanished and died. He also waived his rights to appeal.

Chelsea's parents said they agreed to the deal because they wanted to spare their son the strife of continuing litigation as well as provide Amber's grieving family a measure of peace.

"The Dubois family has been through unthinkable hell the past 14 months," Brent King said at the news conference, reading a joint statement with his wife, Kelly. "We couldn't imagine the confession to Amber's murder never seeing the light of day, leaving an eternal question mark."

Prosecutors said they were confident they could win a conviction against Gardner in Chelsea's death but conceded Friday that they didn't have enough evidence in Amber's killing.

After Gardner, a 31-year-old registered sex offender, was arrested in Chelsea's death in late February, he was named a suspect in the death of Amber, who vanished while walking to school on Feb. 13, 2009.

Gardner led authorities to Amber's bones on condition that prosecutors couldn't use that information against him. They would have to build a case on their own.

At the news conference after Friday's hearing, San Diego County District Attorney Bonnie Dumanis said investigators tried to connect Gardner to Amber's death independently of his confession but were unable to.

"Accepting this plea has been an extremely difficult decision," she told reporters. "We have the evidence to pursue a murder charge against the defendant for Chelsea's murder but not for Amber's murder."

Even if prosecutors rejected the deal, the King family would have had to endure decades of appeals if he was convicted and sentenced to die, Dumanis said.

Maurice Dubois, Amber's father, also appeared at the news conference with Amber's mother and the Kings and thanked law enforcement in a brief statement. He said he was surprised by "this turn of events in the case," which he learned about Thursday.