STOCKTON — San Joaquin County has agreed to a $500,000 settlement of a lawsuit filed 5½ years ago by the mother and sisters of a teenage girl who was murdered in 1985 by methamphetamine-fueled serial killers Wesley Shermantine and Loren Herzog in Linden.

The suit alleged that in 2012, the San Joaquin County Sheriff’s Office exhumed the remains of 15-year-old Jo Ann Hobson in a “careless and wrongful” fashion, commingling her bones with those of other victims.

The Board of Supervisors is slated to sign off on the agreement at its regular meeting Tuesday. The settlement is to be paid from the county’s Self-Insurance Trust Fund.

Hobson disappeared in late August 1985. Her mother, Joan Shelley, and sisters Michelle Loftis and Sandra Hoyopatubbi are listed as plaintiffs in the original complaint filed more than five years ago in federal court. Shelley did not respond to a phone message Wednesday.

The lawsuit stemmed from information received in 2012 by the Sheriff’s Office that suggested unaccounted-for bodies had been disposed of in an agricultural well on Flood Road in Linden.

On Feb. 8, 2012, a county-operated excavator with a 17-foot arm was brought in to remove compressed and heavy foreign material from the well. No human remains were recovered that day.

Officials told family members that if human remains were discovered as the dig continued, the excavation would stop, according to court documents. The suit alleged that a human bone buried about 50 feet deep in the well was recovered on Feb. 11, 2012, but the use of the excavating machine continued for four more days.

“Defendants recklessly, intentionally, and/or negligently caused the skeletal remains of Jo Ann Hobson, a victim of murder, to be chewed up, pulverized, destroyed, crushed and commingled with other unknown murder victims,” the suit said. “This, in turn, caused Plaintiffs extreme shock, horror, distress and permanent psychologic (sic) injury and harm.”

It was another six months before defendants turned over “the chopped up and purported remains of Jo Ann Hobson, by sending them to the mortuary for cremation,” the suit said.

According to the suit, a subsequent evaluation of bone fragments by a professor of forensic anthropology revealed that “at least three, and perhaps more individuals were contained in the body bag of bones Defendants had released for cremation.”

Herzog and Shermantine were believed to have murdered as many as 25 people. The whereabouts of as many as 20 victims are still unknown. Herzog’s conviction was later overturned. He committed suicide in 2012 inside a trailer near Susanville. Shermantine remains on San Quentin’s death row.

Contact reporter Roger Phillips at (209) 546-8299 or Follow him on Twitter @rphillipsblog.