LONDON, SEPT. 8 -- One of three Irish Republican Army members killed by British Army commandos in Gibraltar last March was shot with as many 18 bullets, including four in the head fired at close range as he lay wounded on the ground, an inquest into the deaths was told today.

Alan Watson, the pathologist who examined the bodies, described the death of Sean Savage as the result of a "frenzied attack" in which shots in the back had probably rendered him incapable of moving before four bullets were fired into his head by someone standing above him.

Watson's testimony, on the third day of the inquest being held in Gibraltar, appeared to support charges by the families of the dead that they were killed in a premeditated, cold-blooded attack. Some eyewitnesses have said that two of the dead, Mairead Farrell and Daniel McCann, were trying to surrender when they were shot and that Savage was running away.

The British government has repeatedly maintained that the seven soldiers involved, members of the elite Special Air Service (SAS) regiment, intended to arrest them and fired only after the three made "threatening gestures." The inquest, conducted by Gibraltar coroner Felix Pizzarello before a jury of 11, is empowered to decide whether the killings were lawful.

In testimony yesterday, Gibraltar Police Commissioner Joseph Louis Canepa said that he had signed an order the day before the shootings authorizing the SAS operation but mandating the use of minimum force in arresting the three.

Canepa said that British authorities knew the three were planning a bombing attack against British troops in Gibraltar. Since British briefing officers described the three as armed and "highly dangerous," Canepa said that he authorized the SAS to conduct the arrests since "armed members of the police force would not be able to cope."

The IRA trio had been under surveillance in Spain, he said, and McCann and Farrell were identified as they walked into Gibraltar on March 6. In town, they met Savage, who had parked a car near the governor's residence, close to where British troops were scheduled to parade on March 8.

The three were then observed walking back toward the Spanish border. Based on information from British intelligence officers, Canepa said he believed the car contained a bomb, and that the three should be arrested for conspiracy to murder.

Later yesterday, an intelligence officer identified only as "O" and testifying from behind a concealing screen, acknowledged three "errors" in the intelligence. The officers involved, he said, believed that the three were armed, that they had left a bomb in the parked car and that they carried a remote-control device to detonate it. One day after the shootings, the British government acknowledged that no arms or detonator had been found on the bodies of the three IRA men and that there was no bomb in the car.

Shortly after the deaths, however, the IRA announced that the three had been on "active duty" involved in a bombing mission. Two days later, Spanish police said they found 140 pounds of plastic explosive in a car parked in Marbella, Spain, that was linked to the three.

In the aftermath of the deaths, it appeared the soldiers had mistaken a practice run for the bombing as the real thing. But their alleged belief at the time that a bomb had been set and that the three were armed is central to the government's contention that the use of lethal force was justified.

Watson's testimony today was the first that raised questions about the government's case. Each of the bodies had been hit by a number of bullets in vital parts of the body, far beyond what would have been necessary to incapacitate them. Lawyer Paddy McGrory, representing the families of the dead, indicated in questioning Watson that he believed the three were shot in the back and then given several killing shots to their heads.

Farrell, Watson said, "was hit by five bullets to the face and neck and three in the back. . . . Danny McCann was shot twice in the head and twice in the back." But, Watson said, it was reasonable to assume that they had been shot first in the head, and that the other bullets had entered their bodies as they were falling.

Savage's body was much more badly damaged, Watson said, and included four bullets to the head that could have been fired from above from no more than two feet away.