The star witness in a case against 25 military men and one civilian on trial in connection with the assassination of opposition leader Benigno Aquino Jr. testified today that she was sent to a mental hospital in Hong Kong after twice attempting suicide there three years ago while being held on criminal charges.

The disclosures by Rebecca Quijano came as a defense lawyer cross-examined her in an effort to destroy her credibility as a witness, show an antimilitary bias in her past and cast doubts on her testimony that she saw a soldier shoot Aquino in the back of the head at the Manila International Airport on Aug. 21, 1983.

Quijano has been dubbed "The Crying Lady" because she tearfully told reporters in the terminal of the airport after the shooting, "they have killed him, and yet you are not crying," before she was hustled away by an aide of Philippine President Ferdinand Marcos.

The cross-examination today appeared to shake, but not destroy, Quijano's testimony, as she generally stuck to the story she told the court May 2 in a long-awaited appearance. Defense lawyers for the accused military men initially chose not to cross-examine her but later changed their minds and battled to have her recalled on the ground that they had come up with new evidence. The evidence pertained to her incarceration in Hong Kong in 1982, in connection with the use of counterfeit traveler's checks, applications here for passports and visas under different names and a series of check-bouncing cases against her.

The dramatic high point of today's proceedings came when defense lawyer Rodolfo Jimenez, representing the military escorts who took Aquino off the plane, questioned Quijano about the trip to Hong Kong, which resulted in six months' detention.

Quijano broke down and wept as she confirmed having tried to kill herself twice in May 1982 by slashing her wrists while in detention. She also confirmed that she was brought to the Castle Peak Mental Hospital and examined by a psychiatrist, but she declined to answer further questions on the subject.

"Even if I were the worst person in the world, that doesn't change what I saw" at the airport, Quijano said as she answered questions about her past.

Quijano also testified that her father, a former mayor in Albay Province in southern Luzon and a member of Aquino's old political party, died while in military detention in 1981 after he was arrested on unspecified charges by agents of the Philippine Constabulary's Criminal Investigation Service. The father, Hector Quijano, was found hanging in his cell at Camp Crame on the outskirts of Manila, and the Quijano family has blamed his death on military men.

"Every time I see military men, I am always reminded of the death of my father," Quijano testified. She also said she "idolized" Aquino, but she denied that she equated him with her father and rejected any psychological link between the two deaths.

However, she appeared less definite than when she took the stand last month about what she saw during the Aquino shooting. At the time, she was the first witness to testify that a soldier shot Aquino as he was descending a service stairway in the custody of military guards, moments after his return from three years of self-imposed exile in the United States.

Quijano testified earlier that, watching from a window of the China Airlines plane in which she had been one of Aquino's fellow passengers, she saw a Philippine Constabulary soldier point a gun at the back of the opposition leader's head and simultaneously heard a gunshot.

Today, she said she could not recall many of the details she was questioned about and appeared vague on several points. Asked by Judge Manuel Pamaran, the head of the three-judge panel hearing the case at the Sandiganbayan civilian court, whether she could say with certainty that the shot she heard came from the soldier's gun, she replied, "It happened so fast. I just heard a shot."

"One has to make a reasonable inference that the gun was fired at Aquino's head," said prosecuting attorney Ernesto Bernabe. "It's impossible to expect that she would see the bullet."

According, however, to Ramon Academia, one of the defense lawyers, "What she said was not credible."

Both defense and prosecution lawyers expressed satisfaction with the day's proceedings, which took place in a packed courtroom.

Appearing particularly relieved was Antonio Coronel, the defense lawyer for Armed Forces Chief of Staff Gen. Fabian Ver, the highest ranking officer on trial and a close confidant of President Marcos.

"She has not testified in any manner against my client," Coronel said of Quijano's appearances. He added that, in fact, none of the witnesses presented before the prosecution rested its case today had implicated Ver, who is charged as an accessory in Aquino's murder for allegedly having participated in a cover-up.

Indicating that he expected Ver to be acquitted, Coronel said he would not present any evidence in defense. "You don't defend yourself against nothing," he said.

Today's proceedings, which were beamed live by closed-circuit television to Marcos' Malacanang presidential palace, failed to provide the detailed revelations that Quijano said she would produce about alleged attempts to intimidate or bribe her into recanting her testimony.

Quijano said at a news conference Monday that persons she would not identify had offered her money "not to testify" and that armed men had visited her house looking for her last week.

Lawyers for Quijano said the cross-examination provided no opportunity for her to recount the alleged pressures on her and that they did not wish to put her back on the stand themselves.