PASADENA, Calif. (AP) _ Dr. Theodore Curphey, the pathologist who became Los Angeles County's first medical examiner and presided over the inquiry into Marilyn Monroe's death, has died. He was 89.

Curphey, who died Thursday in a Pasadena nursing home, was succeeded by Dr. Thomas T. Noguchi, who actually conducted the autopsy on Miss Monroe, and who eventually was demoted for mismanaging the coroner's office.

Before Curphey's appointment in 1957, the county office had existed under a public administrator and guardian, not a physician.

It was Curphey who ordered the controversial ''psychological autopsy'' of Miss Monroe after her 1962 death.

On Aug. 17, 1962, he said at a news conference, ''It is my conclusion that the death of Marilyn Monroe was caused by a self-administered overdose of sedative drugs and that the mode of death is probable suicide.''

He was coroner of Nassau County, N.Y., from 1938 to 1957, when the Los Angeles County Board of Supervisors chose him to head the new office.

His changes in procedure ruffled some political feathers, prompting a grand jury investigation. But Curphey and his scientific approaches were vindicated, and his medical team eventually was hailed by scientists as progressive.

Curphey, who also was on the faculties of the University of Southern California, University of California at Los Angeles and Loma Linda University, left the coroner's office Oct. 25, 1967, his 70th birthday.

Seventy was the mandatory retirement age but he served as a consultant in forensic medicine and on the Suicide Prevention Bureau he founded.

Noguchi conducted Miss Monroe's autopsy and therefore received most of the publicity. But it was Curphey who supervised the entire investigation.

The main investigative agency handling the case was the coroner's office, not the police, because it appeared from the start to be suicide.

Curphey appointed a three-member team of mental health professionals to determine what happened, rather than conducting a public inquest with sworn testimony. The move was novel for its time.

The investigation lasted only 11 days. Years later, critics noted that key people, including the late actor Peter Lawford, were not interviewed. Lawford, who talked to Miss Monroe on the phone only hours before her death, was not questioned by police until 1975.

In 1982, the Los Angeles County district attorney's office issued a detailed investigative report that generally supported Curphey's conclusions.

He is survived by a daughter, two sons, six grandchildren and four great- grandchildren. His ashes will be scattered at sea.