But skeptics say that allegations such as Mallah's underscore the danger in relying too heavily on polygraph devices, which are not considered reliable enough to be used in court. At the CIA, for example, hundreds of employees have been placed on administrative leave or removed from sensitive duties since that agency stepped up its use of lie detectors in the wake of the Aldrich H. Ames spy case in 1994. At the FBI, meanwhile, about a fifth of job applicants fail preemployment lie detector tests, according to a report to Congress. Few get a second chance and most are denied jobs, officials said. Polygraph machines, which measure a person's respiration, blood pressure and other physical changes, can be defeated.
Some Web sites brag that people can learn to beat the tests in a matter of hours.
It's far more trouble than it's worth. . . . Polygraph defenders disagree, arguing that if nothing else, the machines serve as a deterrent and can provide crucial clues in intelligence cases. At the CIA, for example, agent Harold J. Nicholson indicated deception when he said in several polygraph exams in 1995 that he had no unauthorized contacts with foreign spies. Ten months later, Nicholson, a former CIA station chief in Romania, was arrested on charges of spying for Russia. At the FBI, polygraphs have been mandatory for new employees since 1994, and have been administered to some agents like Mallah because they have access to sensitive information about a secret program or criminal case.