Kyriakos N. Kotsoglou and Marion Oswald

Are lie detector tests for terrorists really a good idea?

(Getty images)

You might have assumed that the polygraph (or ‘lie detector’ as it is commonly known) was something used only for entertainment on the Jeremy Kyle Show. It is, after all, little more than a relic from the 1920s when people turned to psychic mediums and truth-telling machines in the misguided search for certainty after the horrors of the Great War. So it might come as a surprise that the polygraph has been used by the penal system in England and Wales for more than a decade. The Probation Service, in fact, uses them to monitor sex offenders released on licence. In the past five years alone, 5,228 mandatory polygraph examinations have been carried out on 2,249 sexual offenders, according to the Home Office.

Few people are likely to be concerned about their use on sex offenders; anything that could prevent re-offending is probably assumed to be a good thing. However, there is a new development when it comes to polygraphs that should worry everyone who cares about due process. The Domestic Abuse Bill and the Counter-Terrorism and Sentencing Bill, both in final stages of the parliamentary process, include proposals to use polygraphs to monitor certain domestic violence and terrorism offenders, and individuals who are subject to Terrorism Prevention and Investigation Measures.

Again, you might shrug your shoulders. Does it matter if the polygraph is only used to monitor such unsavoury individuals? Yes, it does. For this development will see our criminal justice system invaded by the widespread use of a wholly unscientific and unreliable machine.

So how do they work? Polygraphs measure physiological data such as heart and breathing rate, blood pressure and sweat. Their design has changed little since a century ago, when William Marston (designer of the polygraph’s prototype and creator of the superhero Wonder Woman) unsuccessfully attempted to persuade a US court in the famous Frye murder trial to accept evidence from his lie detector test.

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