Free Tiger Trap: America's Secret Spy War With China by David Wise

in place while the investigation continued. But Min's access to secrets was discreetly reduced. In Washington, the secretary of energy had to sign off, every six months, on approval for Min to remain at Livermore.
    By early 1981 scientists and engineers at the lab, including Min, were already working on what became the Star Wars program to intercept nuclear missiles. Officials decided that leaving Min on the job had become too risky.
    The time had come, Cleveland decided, to confront Gwo-bao Min. Espionage is a peculiar crime. Unless suspects confess or, as rarely happens, are caught in the act, they may go unpunished. A bank robber may be caught fleeing in a getaway car, an embezzler may be ensnared by an audit. But spies are a different breed, they move in a secret world, often exercising clandestine skills to avoid detection.
    Sometimes a confrontation works. When FBI counterintelligence agents question a suspected spy and reveal how much they know, in some cases even presenting him with surveillance photos, the suspect may feel it is useless to deny the evidence amassed against him. Or the suspect may harbor a hope that his FBI interrogators will offer to turn him into a double agent, working against the other side. At times skilled interviewers, using various ploys, are able to elicit a confession.
    Min was told by lab officials that serious questions had been raised about him by the FBI. As a result, they warned, he could keep his job only if he resolved those issues. He was placed on leave and agreed to talk to the bureau.
    In the first of several days of interviews, Min was asked about the index cards found in his carryon bag and contended that they were just notes he had taken at lectures at the lab. For six hours, he denied knowing Chien Ning or Hanson Huang, then admitted he did but said he knew nothing about any letters from Huang.
    The next day, Min said he had, after all, received a letter from Huang. He agreed to return a third day and produced the show-and-tell innocuous letter. Cleveland asked Min to let the FBI's forensic experts examine the letter, and he consented.
    On the fourth day, Min agreed to take a lie detector test. Cleveland then pulled a rabbit out of his hat and produced a copy of the real, substantive letter that Dan Grove had intercepted with the help of Tommy Tang, the Berkeley student.
    The FBI agents did not want to reveal to Min, however, how they had managed to acquire the letter. They devised a plausible explanation. Chinese characters are frequently written on a pad with preprinted boxes that make it easier to keep the lines straight. Each character, representing a picture of an object or sounds and meaning, fits inside a box. If the substantive letter to Min was written first, as would seem likely, and then ripped off the pad, it might leave an impression on the sheet below on which the for-show letter was written.
    Cleveland told Min that the FBI had retrieved the new letter from the impressions left on the innocuous letter that Min had offered to the agents the day before.
    Min examined the substantive letter closely. Apparently he believed the FBI's invention.
    "I wish to congratulate you," he said. "You have done your job very well."
    Cleveland now thought he had Min on the verge of a confession. But it was not to be. The Livermore engineer said he wanted to talk to his wife before answering further questions. He agreed to meet the FBI agents the next day at a motel, but then telephoned to say he had changed his mind.
    The lab's officials then told Min that since he had not resolved the issues raised by the FBI, he could not remain at Livermore. Min was allowed to resign.
    The tiger had escaped the trap. But the FBI had forced Min out of the nuclear weapons lab and prevented any additional compromise of secrets to China.
    Some who knew Gwo-bao Min argued that he may not have set out to spy for China, but had traveled to Beijing in the hope of making business contacts and once there