Mandatory polygraph testing for sex offenders is set to be rolled out across England and Wales following a successful pilot scheme, ministers say. BBC.
The trouble with lie detectors is they aren’t fool proof!
When a well-trained examiner uses a polygraph, he or she can detect lying with high accuracy. However, because the examiner’s interpretation is subjective and because different people react differently to lying, a polygraph test is not perfect and can be fooled. How Stuff Works.
How Stuff Works is being pretty generous. William G. Iacono of the University of Minnesota writes of Control Question Test polygraphs, by far the most used lie detection method.
Although the Control Question Test may be useful as an investigative aid and tool to induce confessions, it does not pass muster as a scientifically credible test. CQT theory is based on naive, implausible assumptions indicating (a) that it is biased against innocent individuals and (b) that it can be beaten simply by artificially augmenting responses to control questions. Although it is not possible to adequately assess the error rate of the CQT, both of these conclusions are supported by published research findings in the best social science journals (Honts et al., 1994; Horvath, 1977; Kleinmuntz & Szucko, 1984; Patrick & Iacono, 1991). Although defence attorneys often attempt to have the results of friendly CQTs admitted as evidence in court, there is no evidence supporting their validity and ample reason to doubt it. Members of scientific organizations who have the requisite background to evaluate the CQT are overwhelmingly sceptical of the claims made by polygraph proponents. Taylor and Francis via AntiPolygraph.org.
And further Vaughan Bell writes
A 2007 study by psychologist Theresa Gannon and colleagues at the University of Kent tested exactly this effect with sex offenders. Child molesters who were attached to a bogus polygraph admitted higher levels of offence-facilitating thoughts than those who were just given a standard interview.
So if it leads to more information, shouldn’t the police be using it? For those who want to base offender monitoring on a technique that relies on ignorance for its validity, it is unfortunate that none of these details is secret as they’ve been discussed openly in scientific and lay forums for years. Any form of risk management that relies on an offender not knowing about Google is inherently flawed, but perhaps more importantly, we have a responsibility to ensure that the police are not basing public safety on methods that are so easily fooled. The Observer.
Which leaves us with much to worry about any intelligent and predatory sex offender is going to easily fool a polygraph with disastrous consequences.