A former CIA technician who was found dead Oct. 26 on the porch of a rented cabin in rural Virginia died of natural causes, the chief medical examiner for Northern Virginia ruled yesterday.

Kevin Mulcahy, 40, who was to testify for the prosecution this week in the trial of ex-CIA agent Edwin Wilson, died of bronchial pneumonia, complicated by a liver condition common to alcoholism and lung disease, reported Dr. James Beyer.

Federal prosecutors handling the case said Mulcahy's testimony was no longer considered crucial, as his earlier assistance had led to Wilson's arrest and other evidence more important to the case. Wilson was convicted Wednesday of seven counts of illegally shipping four pistols and an M16 rifle to Libya.

After Mulcahy was found hunched against the door of the tiny cottage at the Mountain View Motel Court in Edinburg, a series of lab tests were run by a private firm as part of the autopsy, Beyer said. Those tests, which were to determine if any toxic substances were involved in Mulcahy's death, did not find anything which contributed to his death, Beyer said.

Tests also were conducted at the FBI lab in Washington on items belonging to Mulcahy that were found in the cabin and in the cab of his pick-up truck. Those items included a case of 12 empty fifth bottles of wine, a 12-gauge shotgun and toiletry articles, said Gary Dalton, a Shenandoah County sheriffs deputy. Sheriff Marshall Robinson said yesterday the results of those FBI tests are not yet available.

The medical examiner's report was accepted by Mulcahy's father, Donald, of Annandale. "I have no doubts," said Mulcahy, a former CIA official. "I have to agree with the professionals. I don't know a thing about medicine."

Beyer ruled that the younger Mulcahy died of bronchial pneumonia, an inflammation of both lungs that is often caused by the common cold, acute and chronic alcoholism, malnutrition, debility and exposure. Mulcahy was found at 8:05 a.m. after apparently spending the night outside, clad only in a sport jacket and pants.

Donald Mulcahy has said his son suffered from alcoholism and had recently been depressed and resumed drinking.