Prince George's State's Attorney Arthur A. Marshall said yesterday that county police who arrested a nurse for allegedly killing a patient were acting against the advice of his office and that after reviewing the case, he has decided to drop the charge unless police gather new evidence.

The chief prosecutor also said that if the nurse were still being held in jail, he would drop the case immediately.

Jane F. Bolding, a former intensive care nurse at Prince George's Hospital, was charged last week with first-degree murder and released on bond, but "if she were in jail, I would dismiss the charge," Marshall said. He explained that he would not want to keep someone in jail if he was unsure that a crime had been committed.

"We are not satisfied at the moment that we can prove a crime was committed," Marshall continued, adding that the charge may be dropped at a preliminary hearing on April 18. That hearing is to determine if prosecutors have probable cause to take the case to trial.

Marshall added that dropping the charge at the hearing does not preclude police from continuing their investigation or charging Bolding at a later time.

Maj. James Ross, head of the county police Criminal Investigation Division, said the officer who charged Bolding was not aware at the time that one of Marshall's assistants had advised against charging her.

Police charged Bolding, 27, last Wednesday in the death of Elinor S. Dickerson last September. Police said Bolding admitted giving the 70-year-old woman a lethal injection of potassium, causing a massive heart attack, to relieve her of "further pain and suffering." Police also are investigating a number of other patient deaths at the hospital.

Marshall said yesterday that a judge may question the validity of Bolding's reported confession because it was given after Bolding was questioned for at least 24 hours. Moreover, he said he cannot prove at this time that Dickerson was murdered.

"We have a person who died of natural causes," Marshall said, alluding to the hospital death certificate. "We have to have someone testify that the cause of death was a homicide." Police probably will seek a post-mortem examination of Dickerson, he said, but he is not sure whether that would prove anything.

Dr. Robert Karnei, chief of the Armed Forces Institute of Pathology at Walter Reed Army Hospital, who is not involved in the case, said, "Exhumation at this time would not be of any value at all."

Karnei explained that the presence of embalming fluid in Dickerson's body and the deterioration of her blood cells since her death would make it virtually impossible for doctors to determine whether there was a potassium overload.

Fred Joseph, Bolding's defense attorney, said he was encouraged by Marshall's statements yesterday.

While police were questioning Bolding last week, Assistant State's Attorney Norman Kiger went to the station in Forestville and advised police not to arrest her at that time, according to Marshall. Kiger said yesterday he did not believe Bolding was a danger to the community, and that police could have continued their investigation without arresting her.

Kiger also said yesterday he was concerned that "in order to proceed with prosecution, we'd have to be able to show that [Dickerson's] death certificate was inaccurate or incomplete." Later he said, "the whole case is going to hinge on medical testimony."

Kiger said police often call prosecutors for advice in pursuing cases such as this one, and that the police usually follow that advice.

Maj. Ross said that while Kiger was advising police at the Forestville station, the officer who a short time later filed the charge against Bolding was at a court hearing in Upper Marlboro.

Regarding Marshall's statement that the charge will be dropped unless new evidence is gathered, Ross said: "We are presently gathering information regarding a very complex matter. We hope to have the necessary information available for the state's attorney to proceed with the April 18 . . . hearing."