The Admissibility of Polygraph Evidence in English Criminal Proceedings
| Author | Michael Stockdale,Don Grubin |
| DOI | 10.1350/jcla.2012.76.3.771 |
| Published date | 01 June 2012 |
| Date | 01 June 2012 |
| Subject Matter | Article |
The Admissibility of Polygraph
Evidence in English Criminal
Proceedings
Michael Stockdale* and Don Grubin†
Abstract The belief that polygraph evidence is inadmissible in English
criminal proceedings has as its basis a variety of common law exclusionary
evidential rules. In reality, this view is backed up by very little English case
law. Further, several of the relevant common law rules have been mod-
ified by statute, have become obsolescent or, dependent upon circum-
stances, may not always exclude polygraph. Moreover, it is necessary to
distinguish expert evidence based on the pass–fail results of a polygraph
examination (which, if admissible at all, would appear only to be admiss-
ible in very limited circumstances) from evidence of statements made by
the subject of the polygraph examination (which may be admissible in a
wider variety of circumstances).
Keywords Evidence; Polygraph; Truth drug; Hypnosis;
Admissibility
The suggestion that polygraph evidence could potentially be admissible
in English criminal proceedings is one that an English judge, barrister or
solicitor might easily dismiss without the need for extensive analysis, it
being ‘trite law’ that such evidence is inadmissible. In reality there is
very little direct English authority to this end. For example, Archbold,1
the leading work for criminal practitioners, states that, ‘Evidence pro-
duced by the administration of a mechanically or chemically or hypnot-
ically induced test on a witness so as to show the veracity or otherwise
of that witness is not admissible in English law’, citing Fennell v Jerome
Property Maintenance Ltd.2This, however, is a first instance civil decision
which involved a ‘truth drug’. Thus, Phipson on Evidence notes that,
‘There is as yet no reported English authority on the admissibility of tests
conducted with the aid of polygraphs (lie detectors) for the purpose of
assessing the credibility of a witness’.3While Commonwealth author-
ities have ruled that the admissibility of polygraph evidence is not
permissible at common law, in the context of English law, the common
law rules on which this proposition is based have been modified or
replaced by statute, have become obsolescent, or do not provide an
absolute bar to the admission of polygraph evidence in all
circumstances.
* Director of the Centre for Criminal and Civil Evidence and Procedure, School of
Law, Northumbria University; e-mail: m.w.stockdale@northumbria.ac.uk.
† Professor of Forensic Psychiatry, Newcastle University; e-mail:
don.grubin@ncl.ac.uk.
1 James Richardson QC (ed.), Archbold: Criminal Pleading Evidence and Practice (Sweet
and Maxwell: London, 2012) para. 8-291 and see also para. 10-70.
2The Times (26 November 1986), QBD.
3 H. M. Malek, J. Auburn and R. Bagshaw, Phipson on Evidence, 17th edn (Sweet and
Maxwell: London, 2010) para. 33-13.
232 The Journal of Criminal Law (2012) 76 JCL 232–253
doi:10.1350/jcla.2012.76.3.771
The purpose of this article is to consider whether polygraph evidence
is potentially admissible in English criminal proceedings. To do so it is
first necessary to examine English and Commonwealth case law con-
cerning the admissibility of polygraph evidence together with two other
procedures with which it is often linked in legal thinking—the admin-
istration of drugs intended to elicit the truth and hypnosis. We will then
identify the common law rules that potentially prevent its admissibility
and examine each in turn to determine the extent to which their
operation, in the form in which they exist in the modern English law of
evidence, does in fact render polygraph evidence inadmissible.
The nature and validity of polygraph evidence
The polygraph is colloquially known as a lie detector, but it does not in
fact measure lies. Instead, it is an instrument that records physiological
changes associated with activity in the autonomic nervous system—a
part of the central nervous system, largely outside conscious control,
that regulates the body’s internal environment. The autonomic nervous
system responds to stress by enhancing arousal: for example, there is an
increase in the supply of blood and oxygen to the muscles through
changes in cardiovascular and respiratory activity, digestion and other
less important visceral activities are slowed, and sweat glands are primed
to dissipate heat generated by the rise in metabolism.
Polygraphy is based on the notion that the act of deception produces
a stress response in the automatic nervous system that can be recorded
and then interpreted by the polygraph examiner. It is not known
whether this arousal is caused by the fear of deception, orientation to an
issue of emotional salience and ‘threat’, increased ‘cognitive work’
involved in deception, or some other mechanism. This absence of a well-
defined theoretical basis to polygraphy, and the lack of a specific physio-
logical ‘lie response’, are often cited by critics of the procedure.4
Proponents counter that while the responses measured by the poly-
graph are neither unique to deception, nor always engendered by it, the
aim of the polygraph examiner is to establish a ‘psychological set’ in the
examinee that increases the likelihood that any observed arousal is
caused by deceptive responding.
The polygraph examination consists of a pre-examination interview,
the test itself where an examinee responds to a small number of ‘yes’ or
‘no’ questions while attached to the instrument, and a post-test ‘debrief-
ing’ interview that takes place after the polygraph charts have been
analysed. In addition to the decision of whether the examinee has been
truthful or deceptive to the questions asked (an ‘inconclusive’ finding is
also possible), any disclosures made during the pre- or post-test inter-
views are noted.
Polygraph accuracy is the subject of long-standing controversy, but a
definitive review undertaken by the American National Academy of
4 National Research Council: Committee to Review the Scientific Evidence on the
Polygraph. Division of Behavioral and Social Sciences and Education, The Polygraph
and Lie Detection. (National Academies Press: Washington, DC, 1986).
Admissibility of Polygraph Evidence in English Criminal Proceedings
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