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When the detector lies: why polygraph use will be restricted



Developed from an idea by William Marston, the creator of Wonder Woman, the polygraph has long been a feature of Hollywood films, detective novels and more recently daytime talk shows. But serious questions have been raised about the use of lie detectors when it comes to the criminal justice system. Those involved in the Home Office’s study into the use of the technology with convicted sex offenders admit that doubts over its accuracy mean it should not be used as an investigative tool or evidentially. However they believe regular polygraph testing is an effective way of monitoring paedophiles and protecting children. Don Grubin, forensic psychiatrist at Newcastle University, who is in charge of the government’s pilot scheme, which aims to test 300 paedophiles, said the polygraph should be seen as a “truth facilitator” rather than a lie detector. “It encourages these guys to disclose information which is useful in treatment and supervision,” he said. In the US, where polygraphs are used in parole treatment for sex offenders, there have been high profile failures in the technology and how it is read. Aldrich Ames, a CIA officer turned Soviet spy, twice passed polygraph tests before being caught in 1994. When the physicist Wen Ho Lee denied leaking nuclear secrets to the Chinese he passed a polygraph test. A second examiner from the FBI looked at the same results later and concluded Lee had lied. But Daniel Sosnowski, a member of the American Polygraph Association, who has been advising the Home Office for four years, said polygraphs were 90% accurate as long as the results were read properly. “You are always going to have false positives and false negatives. But this is something you have with medical testing too.” For the Home Office study five machines have been bought from a company in Indiana for around $5,500 (about £3,000) each. The volunteer is attached to the machine, which measures heart rate, respiration and sweating. The validity of the results in work with criminals has polarised academic opinion. Paul Seager, senior lecturer in social and forensic psychology at the University of Central Lancashire, said that those against testing point to the high level of false positives. “In other words, you are wrongly accusing lots of people.” Richard Wiseman, a psychologist at the University of Hertfordshire, who specialises in deception, said: “Paedophiles are living a life of deception. It may be that in using polygraphs you would be missing skilled liars.”

The Guardian