Deputy District Attorney Dori Ahana made the announcement at Naso's arraignment in Marin County Superior Court.
Naso, 78, of Reno, re-entered not-guilty pleas to charges that he murdered four Northern California women, two from the Bay Area, between 1977 and 1994.
Naso waived his right to have a trial within 60 days. He said he needs four weeks to prepare a motion to dismiss the charges against him.
Judge Andrew Sweet set March 28 for a status report on that motion and to set a trial date.
Ahana told the judge prosecutors expect the trial to last four months.
Naso is charged with the murders of Roxene Roggasch, 18, of Oakland, in Marin County in 1977; Carmen Colon, 22, in Port Costa in Contra Costa County in 1978; and Pamela Parsons, 38, and Tracy Tafoya, 31, in Yuba County in 1993 and 1994, respectively.
In addition to the four murder charges, he faces a special-circumstance allegation of committing multiple murders, which makes him eligible for the death penalty if convicted.
Prosecutors had not said publicly until today whether they would pursue the death penalty.
He was ordered to stand trial for the killings in January at the conclusion of a nine-day preliminary hearing that included testimony by his ex-wife Judith and investigators, who said semen found on pantyhose Roggasch was wearing contained DNA that was likely Naso's.
Naso has been acting as his own attorney, and at a hearing earlier this month, Sweet found Naso to be capable of continuing to represent himself as the case proceeds to trial.