A Philippine court today acquitted armed forces chief of staff Gen. Fabian C. Ver and 25 other persons, all but one of them military men, of all charges in the 1983 assassination of opposition leader Benigno Aquino.

With the defendants standing before them in a crowded, muggy courtroom, a three-judge tribunal ruled that "evidence overwhelmingly points" to Rolando Galman as the man who shot Aquino at Manila International Airport. Galman, who the military claimed was a Communist agent, was immediately killed at the scene by security personnel.

Delivering their verdict after a seven-month trial, the judges dismissed as insupportable the prosecution's contention that Aquino was shot by one of the security men who escorted him off a jet that had returned him home after three years of exile in the United States.

The verdict, aired live on television, seemed certain to raise cries of outrage from Filipino opponents of President Ferdinand Marcos, who have accused him of manipulating the investigation and trial.

The verdict is not likely to be well received in Washington. The Reagan administration and the U.S. Congress have viewed the trial and the future role of Ver as a crucial test of Marcos' commitment to reform.

In its verdict, which took the clerk of the court more than two hours to read, the court said, "It is safer to err in acquitting than in punishing."

Ver is a cousin and close confidant of Marcos. He went on temporary leave of absence from his post as chief of staff after he was indicted in January as an accessory in an alleged conspiracy to cover up the murder.

As he left the courtroom today, he said, "Thank God, it's all over." Ver also said he was "never in doubt" about the verdict.

Marcos has said Ver would be reinstated automatically if acquitted but lately has been hinting that Ver would be moved to some less visible post as part of a general reorganization of the military command.

Ver's acquittal had been widely predicted because the Philippine Supreme Court in August upheld the trial court's ruling that threw out most of the evidence against Ver. But many people here believed that several low-ranking military men who were at the scene of the shooting would be convicted.

After the verdict, Aquino's widow, Corazon, said: "Justice is not possible so long as Mr. Marcos continues to be head of our government." She said the murder was a "heinous crime committed by a handful of Mr. Marcos' most loyal henchmen. I now appeal to the decent elements of the military to help me get the facts and truth."

About 100 protesters demonstrated outside the courtroom while the verdict was being read.

The 26 defendants, who included four generals and two colonels, were indicted after a special fact-finding board concluded that a military conspiracy was behind Aquino's murder.

Much of the prosecution's case rested on testimony from a Filipino woman who hid out during the board's inquiry but then surfaced to testify in court that she had seen a soldier shoot Aquino as he was being escorted down a staircase onto the airport's tarmac.

The court today dismissed her testimony as not credible, citing her "emotional instability," an attempted suicide and trouble with the police. It also said she showed "personal animosity toward the military" and viewed Aquino as an "idol."

The court also cited the lack of blood on the staircase and other medical and ballistic findings as evidence that Aquino could not have been shot on the staircase.

The court cited testimony from several soldiers, who said they had clearly seen Galman shoot Aquino, as carrying more credibility.

Aquino was shot in the head on Aug. 21, 1983, at Manila's International Airport within seconds of stepping off a China Airlines flight that had brought him back from self-imposed exile in the United States.

At the time of his death, he was in the custody of military security personnel who had boarded the jet after it landed. People inside the jet heard a fusillade of shots almost immediately after Aquino began walking down the steps. When the shooting was over, Aquino and Galman lay dead on the tarmac.

The military initially claimed Galman was a Communist agent who had slipped through airport security, shot Aquino and then been killed by security personnel. But allegations quickly surfaced that one of the escorts had shot Aquino and that Galman had been brought to the scene as a ploy.

The murder of Aquino, a former senator who had spent more than seven years in prison under Marcos, enraged millions of Filipinos and led to a torrent of antigovernment demonstrations.

Marcos at first endorsed the military version, then bowed to intense pressure for an independent investigation. Marcos eventually appointed a five-member fact-finding board headed by retired appeals court justice Corazon Agrava. The board heard testimony from 193 persons, including Marcos' wife Imelda and Ver, in proceedings followed attentively by the nation.

Evidence mounted casting doubt on the military's explanation.

In October last year the Agrava board officially concluded that Aquino was shot by one of his escorts as a result of a military conspiracy and that Galman was set up to take the blame. Board members disagreed, however, on how high in the military the conspiracy went.

The board turned over its evidence last year to a government ombudsman empowered by Marcos to take the case. On Jan. 23 this year, prosecutors indicted 25 military personnel and one civilian on murder conspiracy charges. Seventeen were named as principals in the alleged plot while nine, including Ver, were named as accomplices or accessories.

On authority from Marcos, the case was tried before a panel of three judges in a special court set up in the 1970s to try cases of government graft. The trial ended in mid-September after seven months.

Nearly all prosecution evidence came from the civilian board, except for the appearance of the elusive witness, Rebecca Quijano, known as the "crying lady." She testified that she saw a soldier shoot Aquino in the back of the head as he was being taken down.

As a result of her testimony, the prosecution, in its summary memorandum in October, named one of Aquino's escorts, Philippine Constabulary soldier Rogelio Moreno, as the opposition leader's assassin.

The evidence against Ver and seven other officers was based on a report by four of the five members of the fact-finding board. The report includes allegedly self-incriminating testimony, documents and other evidence produced in response to subpoenas from the fact-finding board.

This summer, prosecutors rejected the affidavits and offers to testify from six U.S. servicemen concerning the mysterious scrambling of Philippine Air Force fighters as Aquino's flight was approaching Manila International Airport.

One Philippine intelligence source has said the scramble was not aimed at diverting Aquino's flight but at intercepting a light private plane to verify that he was not on board.

Diplomats have said the U.S. airmen's testimony could have pointed to a wider conspiracy in the Aquino case and implicated high-ranking Philippine officers.