Brandon P. Smith, 31, is accused of fatally stabbing Christensen, allegedly to keep her from testifying.
On Wednesday, Ashton pleaded guilty to one count of aggravated murder for Jerden's death, attempted aggravated murder for wounding Fiske during the 2010 apartment shooting, and possession of a controlled substance, Filter told The Tribune.
The aggravated murder charge relating to Christensen's death was dismissed, Filter said, because prosecutors believe Smith was responsible for her death.
"[Ashton] has taken responsibility for the actions that he did," Filter said. "Christensen's family agreed to the plea agreement. We feel like we're going to focus on the person who is culpable for Jerrica's death... We agree that Paul Ashton's culpability for the death of Jerrica was as an accomplice... and that he did not directly cause her death."
No clear motive has been revealed for the two slayings, but Jerden had been staying with her boyfriend at Ashton's apartment and she was moving out when violence erupted, according to Ashton's former attorney Aric Cramer.
Filter said that as part of plea agreement that spared Ashton the possibility of facing the death penalty, he will recommend to the judge that Ashton be sentenced to life without the possibility of parole when he is sentenced at Aug. 11.
Ashton is also set to be sentenced that same day in federal court for the Oct. 21, 2010 murder of Bradley Eitner, 43.
Ashton admitted in May in U.S. District Court to kidnapping Eitner and aiding in his murder. According to court documents, Eitner had passed out at Ashton's apartment that evening and Ashton, with the help of another individual, carried Eitner to his truck outside the residence. On the way out the door, Ashton banged Eitner's head against the door frame "at least once," according to a court document.
Ashton placed Eitner in the truck bed and slammed the tailgate against the man's head "at least once." After driving around for a while, the unidentified man with Ashton urged him to take Eitner to a hospital or the local homeless shelter. Ashton apparently became enraged and said, "I'm going to smash his head with a rock and beat his head with a shovel."
He stopped the truck, got out, retrieved a rock and struck Eitner in the head with it.
Ashton then dropped the other man off at his own home and picked up another individual, who is identified in court documents as Ashton's "accomplice."
The two drove to a secluded location in the Arizona desert and helped Eitner, who was still alive at that point, out of the truck.
"My accomplice then shot Mr. Eitner twice with a rifle, and at least one shot hit Mr. Eitner in the head," Ashton said in a plea statement. The accomplice pushed Eitner off an embankment, where he became wedged in a rock crevice.
Eitner's body was discovered on March 11, 2011. An autopsy determined he died as a result of blunt force head trauma and a single gunshot wound.
Ashton entered guilty pleas to kidnapping resulting in a death and aiding in the use of a firearm during a violent crime.
Federal prosecutors will recommend that Ashton get life in prison for the kidnapping charge and 10 years for the firearm charge, both the mandatory-minimum sentences allowed by law, and that the penalties run consecutively. Filter said they will ask that Ashton be allowed to serve his sentence for Jerden's murder in federal prison.
A five-day preliminary hearing for Smith, who is charged with aggravated murder and aggravated assault, is set to begin on Oct. 7.