Rebecca Quijano has used a number of aliases in a line of work that remains something of a mystery, but the one that most Filipinos now know her by is one she never wanted: "the crying lady."

The title may be worthy of a suspense novel. But in fact it derives from the Philippines longest-running real-life mystery, the murder in August 1983 of opposition leader Benigno S. Aquino Jr. as he was leaving a plane in the custody of military guards at the Manila International Airport.

It was fellow passenger Quijano, sobbing uncontrollably, who told reporters in the airport terminal afterward, "They have already killed him, yet you are not crying," before she was hustled away by a military aide to President Ferdinand Marcos and later went into hiding.

Now, the prospect that she may be the only witness able to identify Aquino's killer has shifted public attention to her anticipated testimony in the case, which is dragging into another year with proceedings under a government ombudsman and an expected trial.

In October an official fact-finding board implicated 25 military men -- including three top generals -- and one civilian in the murder of Marcos' political archrival. Marcos in effect relieved the military men, among them his longtime close confidant, armed forces Chief of Staff Gen. Fabian Ver, and ordered complex legal proceedings involving an investigation by the ombudsman and "immediate trial" of the accused before a civilian court that normally hears petty corruption cases against government officials.

The proceedings quickly became bogged down in the legal wrangling and general inertia that seems to plague the Philippine judicial system, and some opposition cynics expressed suspicion that maybe that was the whole idea.

Enter "the crying lady," as she has been dubbed in the local press.

After having been sought in vain by the fact-finding board's lawyers to testify in its nearly year-long proceedings, she suddenly surfaced Dec. 12, when she was arrested by National Bureau of Investigation agents at a hotel in Manila. She reportedly had gone to the United States and returned here in September.

Described as a "businesswoman" with U.S. residency, Quijano, 32, was wanted here on several longstanding swindling and car-theft charges. But she apparently had other reasons to fear the law.

According to her lawyer, Raul Gonzales, Quijano's father died in detention after he was arrested in 1981 on swindling charges by the military's Criminal Investigation Service. The agency said he hanged himself, but his family harbored doubts.

So when the Criminal Investigation Service invited Quijano to answer questions about the Aquino assassination after her arrest, she sought protective custody with the National Bureau of Investigation, a police body. She remains under the bureau's protection, barred from leaving the country by government order based on three old charges still pending against her.

Since her arrest, she has written a letter to local newspapers asking President Marcos to order the military to stop investigating the Aquino assassination and leave it to the government ombudsman. Otherwise, she said, she might not agree to testify before the ombudsman.

In any case, she wrote, she already has written an account of what she saw, as a passenger aboard the China Airlines plane that brought Aquino to Manila from Taipei, when the opposition leader was killed by a single shot in the back of the head seconds after leaving the aircraft.

The military blamed the murder on Rolando Galman, a professional gunman allegedly hired by communist rebels. But the fact-finding board concluded, based largely on circumstantial evidence, that Aquino was killed by one of his military escorts and that Galman, who was immediately gunned down, was set up as a patsy.

Quijano said she had sent her account to a friend in the United States with instructions to release it to the press if "anything violent" happens to her.