The Experiment with Lie Detection Should Be Ended

The polygraph machine – or ‘lie detector’ – has long been tied-up with sex and sexuality, from the use of the device to out homosexuals during McCarthyist witch-hunts to the recent use of polygraphs to monitor convicted sex offenders. Reports of the success of this programme warrant scepticism and careful analysis, not least because the machine doesn’t detect lies, but also because the history of polygraphy tells us that it is a slippery slope from using it in one area to its spread into all realms of social life.

The majority of psychologists will tell you that the polygraph machine does not work – and they are right. It doesn’t detect lies. Nonetheless, in the past century the machine has been used in a variety of situations in the United States, including for job applicant screening, police investigations, in agreeing divorce settlements, or for resolving family and business disputes. Its proponents have sold it more on a political promise than on scientific credentials, as a tool in the fight against crime, to challenge police corruption or to combat terrorism. Sex offenders are just the most recent group to play a role in these scientific and political fictions.

In the UK we have thus far been more circumspect regarding lie detection, and thanks to this scepticism the polygraph does not have the kind of mythic quality that it seems to engender in American hearts. However, there are a few areas in which examinations have crept in, chief amongst them being their use to monitor sex offenders post-probation. After changes to the Offender Management Act in 2007, trials were run and eventually polygraphy was rolled-out across the UK. It is now reported that through these routine examinations 63 of 492 convicted sex offenders have been returned to prison after they admitted to breaches of their probation conditions.

On the face of it, of course, this is a good thing, for nobody could deny that sex offenders who breach their parole conditions should be returned to prison. However, there are serious concerns that should be raised about the efficacy of this technique and its longer-term consequences.

The chief problem is the kind of evidence the polygraph produces. The thrust of the research into polygraphing sex offenders aims to assess how far the machine goes to elicit so-called ‘clinically significant disclosures’. These are effectively confessions of one kind or another, and are typically used to evaluate the offender’s riskiness, change treatment strategies or alter probation conditions.

In other words, the validity of the polygraph is seen to rest not so much on whether it can detect lies but whether it can get offenders to make more disclosures about their behaviour. However, reports from the programme’s trial show that most disclosures are not made during the actual test but in the pre-test or post-test interviews. The polygraph’s role is less lie detector and more threat, used to induce disclosures. In this way, is works only so long as offenders believe that it works and any disclosure made is treated as evidence that offenders are being more honest.

This is not a good basis for making crucial legal decisions: sex offenders returned to prison are likely to learn from each other that the machine does not work and develop ways to cheat the test. There are courses one can take and books one can read about beating the machine. The fact is that the use of the polygraph in this context, as in others, is based on a game of bluff – who can convince whom that they are telling the truth? The examiner, when they say that the machine is infallible, or the examinee, when they say that they have not lied?

It is distinctly unwise to rely on such a game of bluff, even if only as an additional method for helping to determine risk. Offenders will, over time, adjust their strategies for getting through probation and back into the general population. Most sex offenders are already skilled liars and will not buy into the lie of the lie detector for very long.

It is also important to take into account the situation in which this technology has taken root. Lie detection was first considered in the UK at the peak of a media-provoked cycle of one-upmanship between Labour and the Conservative Party over who could be toughest on crime, a contest which has escalated over the last two decades and has always been most vociferous when it has focused on paedophiles. As former Justice Minister for the Coalition government, Jeremy Wright said of the implementation of the programme: “this will give us one of the toughest approaches in the world to managing this group.” Toughness cannot be an end in itself. This is not the kind of politics which we need in such a sensitive and complex situation – where the prevention of crimes against children is at stake cooler heads must prevail. Lie detection breeds confidence in probation decisions where no confidence is justified.

We have to be careful not to let the use of the polygraph in one context help it spread to another. In the USA the spread of polygraph exams began in the 1940s and today millions of exams are conducted every year by thousands upon thousands of examiners in many different situations. In some cases, it was the use of the lie detector by government departments like the CIA, FBI or Department of Energy, which helped justify its spread. Trial courts heard that since the machine was trusted in the most sensitive parts of government security, it should also be used as evidence of guilt or innocence. The machine is now used in criminal justice systems far more regularly than is realized by most observers. And, in the police interrogation room, there are more than a few cases in which the polygraph exam has been directly responsible for the production of false confessions.

We must guard against the use of lie detection in the UK, no matter the context, but especially in those situations in which the risks are so high. The crimes of sex offenders warrant surveillance during probation, but the polygraph does not warrant our credence. For it does not work, and sooner or later it will be found within a divorce proceeding, a job interview or a routine matter of airport surveillance, and your heart will be the one that is beating out a rhythm on the examiner’s chart.