FAIRFIELD -- At his murder arraignment Friday, ex-death row inmate Dennis Stanworth proclaimed, "It's the third time," and, "I plead guilty to everything" before his public defender could finish seeking a one-week delay in the case.

According to Solano County deputy district attorney Karen Jensen and a one-count murder complaint, Stanworth, 70, killed his 90-year-old mother "on or about" Nov. 6, at his house on the 2500 block of Marshfield Road in Vallejo and kept her body there until his confession Wednesday. The body was discovered outside the house in the upscale Hiddenbrooke neighborhood, Jensen said.

Jensen declined to comment further about the unfolding investigation -- including how the death occurred or had been concealed.

Sitting in a wheelchair, Stanworth appeared frail in court and complained that he couldn't hear the proceedings. After several outbursts, his attorney, Solano County chief deputy public defender Oscar Bobrow, urged him to remain silent.

No formal plea was entered, but Stanworth's statements in court could be used against him, Jensen said. Solano County Superior Court Judge Donna Stashyn scheduled another arraignment hearing for Jan. 18.

Stanworth was arrested Wednesday after he called Vallejo police and said he had killed his mother, Nellie Turner Stanworth, who had lived for several years at the Olympia Mobilodge of Napa in American Canyon. Other park residents reportedly had been told by Stanworth that his mother had passed away about six weeks ago, after he had helped her move out of her home.

Stanworth was convicted in 1966 of murdering Susan Muriel Box, 15, and Caree Lee Collison, 14, De Anza High School students he picked hitchhiking. He drove the girls to the shoreline, forced them to undress, and shot them, after which he raped Box.

Stanworth pleaded guilty and was sentenced to death twice, but both death sentences were later reduced to life imprisonment with the possibility of parole. Stanworth was paroled in 1990 and was required to register with the Vallejo Police Department as a sex offender.

Stanworth is eligible for the death penalty because he is also charged with the special circumstance of the two previous murders.

The Solano County Coroner's Office completed an autopsy of the mother's body earlier Friday. However, the final autopsy report has not been released.

After the hearing, Bobrow declined to comment about the case or Stanworth's health.

Jensen said Stanworth is hard of hearing and has "health issues," but she had no further information about his condition.

Stanworth had been living at the Hiddenbrooke residence with his wife and father-in-law. It remains unclear if they had any role in the case.

"The investigation is still ongoing," Jensen said. "It is unclear at this time what they knew or when they knew it. So I think only time is going to tell with further investigation what they knew."

Contact Tony Burchyns at (707) 553-6831. Follow him at Twitter.com/tburchyns.