A federal judge today ordered that former Los Alamos National Laboratory physicist Wen Ho Lee remain in jail without bail pending trial on charges he downloaded vast quantities of secret nuclear weapons data from the lab's secure computer system and transferred them to unsecure portable computer tapes.

At the end of a three-day detention hearing, Judge James A. Parker held that no reasonable combination of restrictions on Lee's actions outside jail would be sufficient to safeguard national security, given Lee's inability to account for seven tapes containing enough information to design and construct a sophisticated thermonuclear weapon.

"The danger," Parker told a packed courtroom, "is presented primarily by the missing tapes" and Lee's refusal to state when, where and how he disposed of them.

Parker urged prosecutors to take Lee up on his standing offer to take a polygraph examination on the question of what became of the tapes. Parker said that if a passing score by Lee allayed the government's concerns about the tapes, he could reapply for bail.

Parker also urged the government to consider loosening the restrictions imposed on Lee in custody. The scientist is being held in solitary confinement and is allowed to see his family in the presence of an FBI agent for only one hour per week. A slight man with gray hair and glasses who will turn 60 on New Year's Eve, Lee was whisked out of the courtroom by U.S. marshals moments after the judge's decision as his daughter, Alberta, sobbed in the front row.

Mark Holscher, Lee's lead defense attorney, appeared stunned by Parker's ruling and said he has been waiting since Dec. 10 for the government to agree to polygraph Lee on his statement that he destroyed the tapes.

In refusing to revoke a magistrate's Dec. 13 bail denial, Parker accepted the argument of prosecutors that Lee represents an "unprecedented" threat to national security and would require, were he to be released on bail, 24-hour FBI surveillance to ensure the missing tapes were not passed to a foreign power. Ordering such surveillance as a condition of release, Parker concluded, would be unreasonable and beyond his authority.

U.S. Attorney John J. Kelly told Parker in a lengthy closing argument that "if you have concluded that the risks are sufficiently great that round-the-clock surveillance is warranted, that suggests the defendant ought to be in custody."

John Cline, one of Lee's attorneys, responded that the government had failed to show that allowing Lee out on bail would threaten the community or nation, particularly since he has relinquished his passport and agreed to have his movements and communications restricted and monitored.

Cline repeated Lee's assertion that he has destroyed all of the missing tapes and said the government has produced no evidence to show that the tapes exist, despite an international search by U.S. intelligence and law enforcement. He also said that an exhaustive FBI investigation of Lee involving 60 agents and more than 1,000 interviews has failed to produce any evidence that Lee revealed--or intended to reveal--any of the downloaded nuclear secrets to a foreign government or any other unauthorized party.

Cline said a combination of home detention and electronic monitoring would be sufficient to safeguard the community if Lee is released on bail, adding that 24-hour FBI surveillance would only be necessary if Parker accepted the government's "unrealistic scenarios about what might happen--helicopters landing, abductions by foreign spies, and so forth."

But in the end, the judge accepted arguments made in testimony by a series of nuclear weapons officials about the extreme sensitivity of the nuclear weapons computer data--the equivalent of 800,000 pages--downloaded by Lee.

Paul Robinson, president of Sandia National Laboratories and a former ambassador to nuclear nonproliferation talks in Geneva, testified that the risk to U.S. national security if a foreign power were to obtain the data contained on the seven missing tapes would be "truly a devastating one."

"Those tapes could truly change the world's strategic balance," Robinson testified.

Parker also attached significant weight to the testimony of FBI agent Robert A. Messemer, a Chinese counterintelligence expert supervising the Lee investigation, who said that no combination of restrictions could keep Lee from transferring the missing tapes to a foreign power if Lee were released on bail.

Even an innocuous remark made by Lee to one of his children, Messemer testified, could jeopardize national security. "It could be as simple as saying, 'Uncle Wen says hello,' " Messemer said. "That could be a message telling a third party to do something with those tapes."

Messemer also said that, should Lee be released, the FBI would have to put even more elaborate surveillance in place and would have to assemble teams of Chinese-speaking agents and translators fluent in Mandarin and Cantonese Chinese in order to monitor Lee's communications to ensure he did not turn over the tapes to foreign spies.

"Today, we have the additional risk of hostile intelligence services knowing these tapes exist," Messemer said. "I believe they will act upon the information being released in the media."

Lee has been in jail here since he was indicted Dec. 10 on 59 felony counts of mishandling classified information. Thirty-nine counts involve violations of secrecy provisions in the Atomic Energy Act and carry maximum sentences of life in prison if the government can prove that Lee willfully intended to damage national security by downloading the nuclear weapons data.

Lee was fired from his post in Los Alamos's X Division in March for allegedly tampering with classified documents and failing to report contacts he had with Chinese nuclear weapons scientists during authorized trips he made to Beijing in 1986 and 1988. At the time of his firing, Lee was identified by federal authorities as their prime suspect in a Chinese espionage investigation centering on evidence that China may have stolen design information related to the W-88 warhead, America's most sophisticated thermonuclear weapon.

Despite identifying Lee as an espionage suspect, authorities now acknowledge that they do not have evidence to show Lee passed classified information to China or any other foreign country. Lee's downloading of classified material was not discovered by investigators until late March, weeks after he was fired and publicly identified as an espionage suspect, and Kelly has said in court papers filed here that the charges brought against Lee for downloading nuclear weapons data are unrelated to the earlier espionage probe.

CAPTION: Wen Ho Lee's son, Chung Lee, left, daughter, Alberta Lee, and wife, Sylvia Lee, at U.S. courthouse in Albuquerque.