The government version of the assassination of Philippine opposition leader Benigno Aquino appears in danger of falling apart. Testimony presented in recent months to the Fact-Finding Board investigating the murder has tended to undermine the claim of the Marcos government that Aquino was killed by Rolando Galman, a small-time gunman.
The testimony apparently shifts suspicion to four military men who escorted Aquino from his China Airlines plane at Manila International Airport last Aug. 21 and thus raises the possibility of official involvement in the killing.
Although the board's conclusions will not be announced for several months, any strong testimony alleging military involvement in the killing could have a major effect on nationwide elections scheduled for May 14.
This may have begun to cause the government some concern. Up to now it seems to have kept its distance from the board, which has slowly been picking up credibility after a difficult start last October. In the last few days, however, there have been the first hints of government pressure on the board.
Other testimony has accused Gen. Fabian Ver, chief of staff of the armed forces and an intimate of President Ferdinand Marcos, of involvement in the disappearance of Galman's wife earlier this year. (General Ver was to have testified before the panel Monday but postponed his appearance, citing a ''pressing security matter.'')
And copies of cables sent to Manila by the Philippines Embassy in Singapore suggest that Aquino's return was not a complete surprise: At least while he was in Singapore his movements were being monitored with the help of the Singapore government. The cables are potentially important as they suggest that departments of the government other than the military were involved in checking Aquino's whereabouts.
The official version of the killing says that Galman, disguised as an airport ground worker, was hiding under a flight of stairs leading from Aquino's plane to the tarmac. As Aquino stepped off the stairs, Galman shot him once at close range behind the left ear and was himself killed by security personnel.
The government also claims that its efforts to protect Aquino were hampered by the secretive and circuitous route by which he returned home.
Testimonies before the Fact-Finding Board have cast doubt on several key elements of this version:
Where was Aquino when he was shot?
The government version says he was on the tarmac; both official and nonoffi-cial accounts of the killing agree that only Aquino's military escorts were on the stairs with the former senator. The most detailed contradiction of this comes from a private security guard, Efren Ranas, who was standing by the plane when Aquino disembarked. On March 20, Ranas told the board that he heard the first shot when Aquino was still on the stairs, about four steps from the tarmac.
After the shot, Ranas said, Aquino's head was bent to the left, and the former senator appeared to be supported by two of his escorts. On the last step, Ranas added, the two escorts released Aquino's body, which fell onto the tarmac. Amplifying on earlier testimony, Ranas said he saw blood on Aquino's back while he and his escorts were still on the last step. Much of Ranas's story was confirmed by three colleagues.
A month earlier Fred Viesca, an airport worker, told the board that he saw Aquino falling from the stairs.
Another alleged witness who has not yet been interviewed by the board also says that Aquino's escorts were holding him up. Reuben Regalado, an aircraft technician, spoke to NBC news in Tokyo late last year. He claims to have fled there in fear of his life. Regalado is still abroad.
And where was Galman?
Aquino's autopsy showed he was killed with a shot fired from close range which entered behind the ear and exited at the chin. If Galman was the assassin, therefore, he must have been behind Aquino, as the government claims. Regalado's account challenges this. He claims that he saw no one behind Aquino and his escorts as Aquino began to crumple.
But, he says, he saw Galman - in front of Aquino. By the time Aquino had fallen on the tarmac, Regalado claims, Galman was standing near the Aviation Security Command armored van that was to have taken Aquino into custody. Galman's wrists were apparently being held by someone. Shortly afterward, Regalado says, one of Aquino's escorts - by the description of his sunglasses Sgt. Arnulfo de Mesa - shot Galman.
Another ground technician, Ramon Balang, told the board he had seen Galman standing with a group of soldiers several feet in front of Aquino when the opposition leader was killed.
Even in the original government story it appeared difficult for Galman, who was shorter than Aquino, to fire a shot that penetrated the senator's head in a downward trajectory. If Galman was not even behind the senator, investigators will have to start looking for another killer.
Were Aquino's escorts armed?
They say not, but Regalado says at least one, de Mesa, was.
(Sergeant de Mesa has just been promoted to second lieutenant in the reserves , though he is still confined to quarters pending completion of the inquiry.) Another witness seemed to support Rega-lado's testimony of this point. Benjamin Maluto, a baggage-cart driver, says that shortly after the shooting he heard one escort, probably de Mesa, tell another soldier that he had no more bullets.
The board has already questioned the escorts once in closed-door session and will be calling them again shortly. A source who was present at the escorts' testimony expressed skepticism about it. All were well-trained soldiers, the source says. At least one has been decorated for gallantry in combat. Yet the escorts apparently testified that they panicked and ran when the first shot was fired.
Crucial evidence about the escorts may be announced soon. A tape recording of the killing by a Tokyo journalist picked up unidentified persons shouting in a Filipino dialect. The voices seem to be saying ''I'll do it'' and ''shoot him.'' A Japanese voice expert has compared the voices on the tape with the recorded testimony of the escorts. His report has been delivered to the board, but not yet translated.
Attorney Bienvenido Tan Jr., public coordi-nator for the board, says that government officers have suggested the voices were dubbed on the tape after the killing.
Attorney Tan notes, however, that at least some of the exclamations are audible on a tape made available to the board by Time Magazine's Hong Kong correspondent, Sandra Burton, who accompanied Aquino home.
Was the government tracking Aquino?
Two cables from the Philippines Embassy in Singapore, both dated Aug. 19 and marked confidential, note Aquino's arrival and departure from Singapore. The cables cite the Singapore Foreign Ministry, Singapore internal security, and unspecified Japanese sources for their information. Aquino, the cables say, traveled under an American passport and left Singapore on the morning of the 19 th.
Soon after the assassination a source told this writer that Filipinos visiting Singapore at the time, and who had a family name that might link them to the Aquinos, claimed they were under surveillance, apparently by Filipinos.