A 42-year-old former Annapolis nurse accused of stabbing her elderly mother to death in January 1981 changed her plea today while a jury deliberated her case. She was declared not guilty by reason of insanity shortly thereafter by an Anne Arundel County circuit judge.

Judge Eugene M. Lerner told the defendant, Pearl Rose Holland Ford, that she will be sent to a psychiatric institution for mental evaluation to determine if she is a threat to herself or others.

Based on the evaluation, Lerner will decide whether Ford should be institutionalized and treated for her illness and where.

How long she would remain institutionalized would depend on doctors' judgments of her well-being.

Ford's mother, Muriel Holland, 76, was killed between Jan. 15 and Jan. 20, 1981, in her upstairs bedroom in an Annapolis house she and her daughter shared.

A neighbor found Holland's body, bearing 40 stab wounds, by a neighbor wrapped in plastic garbage bags alongside trash cans in an alley behind the house. Detectives found traces of blood and hack marks on furniture in the bedroom.

A short time later, police arrested Ford, Holland's only daughter and, according to court testimony from two psychiatrists, a previously diagnosed paranoid schizophrenic.

She had refused suggestions throughout the trial by Assistant State's Attorney Ronald Naditch that she change her principal plea from "not guilty" to "not guilty by reason of insanity."

Four hours into the jury's deliberations, she changed her mind after the jury submitted a question to the judge asking for legal definitions of sanity and insanity.

Ford's attorney and the prosecutor said later that the question had been an indication that the jury had already decided her guilt or innocence. The question of sanity was to be decided once guilt was established, attorneys said later.

Ford, who did not take the witness stand in her own defense during the trial, answered questions from the judge. She told Lerner her memory of the time surrounding her mother's death was "almost a blackout."

After Ford changed her plea, the jury was dismissed. Margaret Evans, the jury's foreman, said the panel decided early that the woman was guilty but was split over whether she was sane.