The US government's reliance on lie detector tests has been criticised by an influential panel of scientists. However, they believe it is possible that the tests do have some value in law courts.
The US is the only country to routinely use the tests on thousands of government employees. But lie detector or "polygraph tests" do little more than worry innocent workers who take them and divert resources from more reliable methods of investigating possible security problems, according to a report from the National Academy of Sciences.
The panel, chaired by statistics professor Stephen Fienberg of Carnegie Mellon University, Pittsburgh, was convened following the case of Wen Ho Lee, a Chinese-American physicist who was privy to classified data at Los Alamos National Labs in Albuquerque, New Mexico.
Lee failed a lie detector test and was later convicted on one charge of spying. As a result, in 1999 the Department of Energy instituted regular routine testing of thousands of employees, in a bid to spot spies. The move was attacked by employees.
During the lie detector tests, workers are asked questions such as: Are you loyal to the US government? Do you intend to release classified information in an unauthorized way? Meanwhile, their heart rate, blood pressure, respiration and electrical properties of their skin are monitored.
But the NRC panel reviewed all available studies on polygraph testing and concludes such data correlate far too weakly with the truthfulness of responses to be useful in mass-screening. "National security is too important to be left to such a blunt instrument," says Fienberg.
Lie detector tests can be useful in criminal cases, the panel thinks. But this is because the questions are very specific, for example, asking whether someone attended a particular event.
The Department of Energy says it will consider the report carefully but is not planning to immediately changes its policy. Polygraph testing has not yet identified any member of staff who may be a security threat.