Manila — The likelihood of an independent and impartial inquiry into the murder of Philippine opposition leader Benigno Aquino was seriously undermined over the weekend.
On Saturday, the archbishop of the Roman Catholic Church in the Philippines, an outspoken critic of the government of Ferdinand Marcos, declined to join the presidential commission to investigate the killing. A few hours later, the archbishop, Jaime Cardinal Sin, strongly criticized the Marcos regime, saying that the Aquino murder has led to a ''volatile and potentially dangerous situation'' in the country, and he warned the government that many Filipinos view it as the prime suspect in the murder.
On Friday, former Supreme Court Justice Roberto Concepcion, thought to be the most independent member of the five-man commission named by the President last week, had declined to serve on grounds of ill health. If either Justice Concepcion or Cardinal Sin had agreed to serve, this would have helped dispell doubts about the integrity and independence of the commission's investigation.
Speaking to the Knights of Columbus on Saturday evening, Cardinal Sin, the archbishop of Manila, expressed his fears about the consequences of the murder, criticized domestic press coverage of the event, and urged the government to act in a ''forthright and open manner'' on the case.
So far, the cardinal said, the reaction to the assassination had been muted - ''the shock and dismay stunned the people.'' But this feeling is beginning to wear off. Asking rhetorically what will replace it, the cardinal said, ''The answer to that question, my friends, scares me to death.''
The cardinal said he sensed ''ominous undercurrents'' beneath the discipline and mildness of the crowd that accompanied Aquino's body from the family home to the Santo Domingo church last Thursday. The feeling he sensed - from the Roman Catholic Church's radio coverage, as he was not himself present - was one of ''anger that was building up, of a resentment that was smouldering and which could be set off by the slightest spark.''
''Whether the government likes it or not,'' the cardinal said, ''much of the anger and all of the resentment is directed at it.'' A large number of Filipinos believe that the government is responsible for the ''dastardly and cowardly act at the Manila airport.'' The government therefore must take a lead in investigating the case and defusing the situation.
The cardinal made it clear in his speech that he was not totally satisfied with the government explanation. Sources close to the cardinal suggest this is a considerable understatement.
And Cardinal Sin listed a number of questions the government should answer. They included: How did the gunman slip through the tight security? How did he manage to shoot Mr. Aquino? How did the bullet fired by the gunman manage to enter Mr. Aquino's skull in a downward direction?
The cardinal, who knows the Aquino family well, says the murdered politician was 5 feet 10 inches tall. Original press accounts, he noted, gave the assassin's height as 5 feet 4 inches. Of course, the cardinal added ironically, the accounts were immediately corrected. ''Somehow the assassin, or supposed assassin, grew three inches overnight.'' If the government does not want its credibility to be further eroded, the cardinal said, it should give satisfactory answers to these and other questions.
Cardinal Sin also criticized the Manila press coverage of the sequel to the Aquino assassination.
The killing had produced an outpouring of grief ''the likes of which this country has never seen before,'' he said. The domestic press reporting had, however, so far been ''pathetic.'' There was no mention and no picture of the ''truly large crowd that assembled last Thursday'' to pay respects to Aquino in a North Manila cathedral.
Cardinal Sin concluded by calling for patience and restraint. ''Inflaming Filipinos to fight against other Filipinos,'' he said, would make Aquino's death ''completely meaningless and futile.''
As for the cardinal's invitation to serve on the commission to investigate the murder, a government press release made it clear the cardinal was not consulted about his appointment, and quoted the President as offering his apologies for this.
Cardinal Sin's spokesman said Sunday that the cardinal had phoned the President to decline the appointment on the grounds that he was not a lawyer and had no knowledge of legal procedures. The spokesman also expressed unhappiness with a statement carried Sunday in the official press. The statement had quoted the President's chaplain as saying that the cardinal had originally agreed to join the commission but had then declined due to a previous Vatican commitment.
A spokesman for the cardinal said this version was incorrect.