Zombie technology in the twilight zone: Why polygraphs refuse to die

Activity: Talk or presentationOral presentation


Polygraphs are becoming the new (ab)normal. Despite existing in a ‘twilight zone’ reserved for disputed science, the polygraph (or ‘lie detector’ as it is commonly called) is a technology that refuses to die. On the contrary, polygraphs are enjoying a resurgence in England and Wales, as a weapon in the probation service’s armoury to manage the ‘risk’ posed by an offender. For several years, polygraphs have been used in the monitoring of convicted sex offenders on licence (Offender Management Act 2007). The current Government now proposes similar polygraph schemes for convicted terrorism and domestic violence offenders, following evaluations claiming that offenders who are made subject to polygraph testing are likely to disclose more information than before.

This paper is not really about how the technology ‘works’ (because it doesn’t!). Even one of the early ‘inventors’ of the polygraph, Leonard Keeler, admitted that there is no such thing as a lie detector. Our concerns centre around how the polygraph’s output (i.e. physiological data) are interpreted and instrumentalised in order to extract adverse statements from the interviewee.

The central claim for the polygraph –that the polygraph can indicate deception – is linked to the disputed (and many would say, discredited) assumption that deception can elicit physiological responses in a consistent and reliable way. We will show – including through information obtained from FOI requests submitted to UK Police Forces and the Ministry of Justice - that the use of the polygraph faces all the usual problems, familiar to both evidential contexts and the use of machine learning: lack of validity, lack of consistency, lack of transparency and the need to use deception and psychological manipulation in order to convince the subject that the polygraph works (via the pre-test, alias ‘stimulation’ test). We will highlight the inadmissibility of the polygraph in criminal proceedings, the discouragement of its use in police investigatory processes, the ‘oppressive’ nature of the test and the pressure on the offender to comply with the process. Probation officers, however, can use an indication of deception in test results, and the offender’s reaction to the test process, to initiate further investigatory or intrusive action which could ultimately result in the recall of the offender’s licence based on an assessment of the offender’s risk. (A ‘no deception indicated’ result is taken to mean that the offender is complying with their licence conditions despite the significant doubts over the validity and accuracy of the polygraph, which leads to undetected risks to the public and complacency). This creates, we will argue, a major contradiction which is detrimental to the integrity of the legal order and raises questions on human rights grounds.
Period30 Jul 2020
Event titleGikii 2020
Event typeConference
Degree of RecognitionInternational