In 1983, US President Ronald Reagan issued the National Security Decision Directive 84, which authorized all federal agencies to use polygraphs (commonly known as lie detectors) to test if any of their employees had leaked classified information. As of 4 February 2015, the US Intelligence Community is once again authorized to investigate its members’ potential involvement in the leaking of classified information via the use of the polygraph. The US polygraph examinations are to be conducted in adherence to the standards set by the National Center for Credibility Assessment, which means that any such examination will be based on a Comparative Question Test (CQT), as opposed to a Concealed Information Test (CIT). The CQT and CIT represent the two predominant types of polygraph testing procedures, which use the same physical apparatus, but differ in terms of their theoretical underpinning and commercial/academic utilization.
The polygraph machine was invented in 1921 in Berkeley, California. "Berkeley was a town with a very famous police chief, August Vollmer, and he was in charge of police reform and a leader of police professionalisation in the United States," says Ken Alder, professor of history at Northwestern University in Chicago."He actually wanted to use the science to make the cops more law-abiding themselves, to substitute this new scientific interrogation for what was formerly known as the third degree, which was a way of getting information from people by beating them up." Berkeley police officer John Larson created the first machine, basing it on the systolic blood pressure test pioneered by psychologist William Moulton Marston, who would later become a comic book writer and create Wonder Woman. Marston believed blood pressure changes could show whether someone was lying. The modern polygraph measures a range of physical changes such as pulse and breathing as well as blood-pressure. But the credibility of the polygraph was challenged almost as soon as it was invented.
In 1923, in what became a historic Supreme Court judgement, Frye v United States, it was ruled that scientific evidence, like that obtained through the polygraph, should only be admissible if it was "sufficiently established to have gained general acceptance" in the scientific community. The polygraph was backed by Leonarde Keeler, who in 1930 helped set up the scientific crime detection laboratory at Northwestern, the first forensic lab in the US, a year before the FBI.
In 2003, Gary Ridgway admitted he was the Green River Killer, having murdered 49 women in the Seattle area. Ridgway had passed a lie detector test in 1987, while another man - who turned out to be innocent - failed. It has been argued that psychopaths like Ridgway or serial killer Ted Bundy are able to trick the polygraph because they have lower anxiety levels than normal people but the research into this has had mixed results.
It was not until 1965, 41 years after the Frye standard was established, that the first empirical review of the polygraph was conducted. This occurred when a proposal to use the polygraph to screen federal employees prompted the US Committee on Government Operations to evaluate the relevant evidence. It concluded: ‘There is no lie detector, neither man nor machine. People have been deceived by a myth that a metal box in the hands of an investigator can detect truth or falsehood’.
Modern polygraphs no longer use pens attached to tambours to write in ink onto a roll of paper driven by clockwork in the way the original Keeler polygraph models used to work. Modern polygraphs produce digital outputs that go directly from the measuring instruments into a computer with the appropriate polygraph software.
