The first of two murder trials in the death of Chinese-American writer Henry Liu concluded today, leaving the impression that the Taiwanese government is trying to balance U.S. requirements for justice with the island nation's preoccupation with political security.

The Taipei District Court sentenced two Taiwanese gangsters, Chen Chi-li, a former chief of the Bamboo Union gang, Taiwan's largest underworld gang, and Wu Tun, his deputy, to life imprisonment for the murder of Liu in California last October.

In a civilian trial that lasted only one day, the defendants said they were acting under orders from the director of the Taiwan Ministry of Defense's intelligence bureau, Vice Adm. Wang Hsi-ling.

Wang and two of his military deputies have been arrested and charged as accomplices. A military tribunal is now hearing their case, which will resume on April 12. It is expected to deliver a verdict on April 19.

The case has strained relations between the United States and Taiwan.

For their part, representatives of Liu's family have suggested that the first trial has shed little new light on the key question concerning the extent of Taiwanese government involvement in the murder of an American citizen on American soil.

In Daly City, Calif., Liu's widow, Helen, had mixed feelings about the outcome of the first trial. "On one hand, I believe Chen should have been sentenced to death because this was a well-planned murder," the Los Angeles Times reported her as saying. "But I also think that Chen was just taking orders, and the whole truth never came out."

Should the U.S. Congress decide that the Liu killing is part of a pattern of harassment of U.S. citizens, it could curtail arms sales to Taiwan, expected to reach $760 million this fiscal year.

Security considerations are believed to be one reason why Taiwanese authorities have so far pre-empted U.S. congressional efforts to "return" the two defendants to U.S. jurisdiction, where San Mateo, Calif., authorities have issued warrants for their arrest.

The arrest of Chen triggered a series of disclosures about national security practices in a country where almost every citizen is aware of political surveillance at home and abroad, and where intelligence forces enjoy broad and loosely supervised powers to further the interests of national security. Political analysts say there are many conservatives in Taiwan who, with the support of the large and powerful security apparatus, have opposed the idea of public trials altogether.

Taiwan says its constitution prevents the "extradition" of its citizens, but Washington argues that without formal diplomatic relations, the question of extradition under a diplomatic treaty is irrelevant, and should not present an obstacle to trying Chen and Wu in U.S. courtrooms. A third suspect is believed to be hiding in the Philippines.

The onus, therefore, rests on Taiwan's judicial system to offer a credible alternative in its own courts.

Chen's carefully prepared testimony, often read directly from a notebook in his lap, contradicted subsequent statements from the admiral and his aides on a number of key points. The gang leader testified that Wang recruited him through Taiwan movieland intermediaries and sent him to espionage training school in Yangmingshan, where Wang amplified earlier suggestions to teach Henry Liu "a lesson" with very specific commands to kill the dissident writer.

Wang portrayed the writer as a triple agent, a man who collected information for the Communist Chinese and the Americans as well as Taiwan, according to Chen.

Chen also asserted that Wang provided him with a full dossier on the victim -- addresses of his Daly City home and shop, a map of his home, his photo and daily routine. On returning to Taiwan, the gangster testified, he was met at the airport by one of Wang's deputies, Chen Hu-men, a defendant in the military trial. Chen also says Wang offered him a reward of $20,000 -- a gift he refused.

Chen testified that he did not know Liu, nor did he instigate the idea of teaching Liu "a lesson." He protested that killing a traitor such as Liu was not a crime. "It is because we are afraid that the killing may affect U.S.-Taiwan relations that we have no choice but to confess," Chen said during the military tribunal's pretrial hearing, at which he appeared as a witness wearing a bulletproof vest.

Vice Adm. Wang has denied ordering Liu's killing. Instead, he has alleged that Chen sought him out for espionage training, and then, under Wang's casual approval of the idea of "teaching a lesson," took the initiative to murder the writer.

But no documentary evidence has been produced to corroborate the contacts between Chen and his military intelligence superiors, according to U.S. lawyer Jerome Cohen, a noted expert on Chinese legal affairs who is representing Liu's widow, Helen. Cohen cited the court's failure to produce Chen's diary and a recorded confession made prior to his arrest as important oversights. Cohen also said that the military intelligence bureau's records of Chen's recruitment, meetings or telephone conversations with Wang and his aides were not examined in court.

The police officers who first arrested Chen in November were not called as witnesses. Cohen also questioned the court's decision to interrogate the military defendants in private chambers, without warning to gang defendants or their lawyers. All these were indications that the proceedings were "restricted," he said.

Despite these limitations, the hearings have offered a miscellany of sensitive trivia about intelligence operations in Taiwan.

At one point in his testimony before the military tribunal, Wang said that his bureau has not assassinated any enemies or traitors "in the last 10 or 20 years."

Details of dinners involving the Bamboo Gang members and the defense intelligence staff also confirmed popular suspicions that the mainland origins of both groups feed a close working relationship between the country's security forces and the fast-growing underworld.

However, the court failed to clearly establish a specific, compelling motive for any of the individuals accused. The victim's widow maintains that "powerful figures" plotted her husband's death.

Despite earlier expectations, the trial proceedings so far have not revealed the involvement of higher authorities in the murder.

In searching for a convincing motive, some critics of the Taiwan government point to Liu's project at the time of his death, a biography of a former governor of Taiwan, Wu Kuo-cheng, known locally during his heyday in the 1950s as "Mr. Democracy."

Wu acquired a popular reputation for defending the rights of citizens at a time when President Chiang Ching-kuo was still supervising intelligence operations from an office near the headquarters of his father, the late generalissimo Chiang Kai-shek, according to a local opposition spokesman.

Some here now believe that a biography of Wu would shed unfavorable light on Taiwan's ruling family, and three advance chapters of Liu's unfinished book, published in a local opposition magazine, were banned from local distribution in Taiwan. This thread of speculation has also fueled the rumor that the president's second son, Chiang Hsiao-wu, who currently runs a government-controlled radio station, used his schoolboy acquaintance with the gangster Chen to protect the family reputation.

Chiang has denied any involvement in Liu's murder. His denials have not, however, dampened the widespread feeling that there is more to the story than is emerging from the current proceedings.