Polygraph testing, more commonly referred to as lie detector testing, has become a popular cultural phenomenon particularly due to the significant association with the controversial television programme The Jeremy Kyle Show. Despite this increased prevalence, the admissibility of polygraph testing within the family courts has come into question.
A polygraph machine measures a variety of physiological factors to determine if an individual is lying. Therefore, polygraph tests are based upon the assumption that people emit certain physiological indications when they lie. On this basis of this assumption, the accuracy of polygraph testing has been called into question by many academics and experts. Many experts and academics argue polygraph machines do not have the capacity to detect if an individual is telling the truth; they simply measure an individual’s biological processes to determine if they are experiencing a physiological event, such as an increase in blood pressure or the excretion of sweat. Although such conditions are considered to indicate that an individual is lying, there are numerous factors that can affect the readings detected by a polygraph machine. In light of this, the accuracy of polygraph testing has come under extreme scrutiny, and the scientific certainty of such evidence is uncertain.
The United Kingdom’s regulation of the use of the polygraph testing varies depending on the context. In the criminal justice system, polygraph tests are not admissible are evidence. Despite this, such tests are used in the United Kingdom for the management of sex offenders. Under the Polygraph Rules 2009, the Secretary of State can require certain sex offenders released on license to undertake polygraph testing to monitor compliance with the terms of their license. However, under section 30 Offender Management Act 2007, the results of those polygraph tests and the answers disclosed during the tests are inadmissible in criminal proceedings.
Therefore, in the criminal justice system, polygraph tests are not admissible are evidence. The reasoning behind the inadmissibility stems from the high degree of burden of proof. In criminal proceedings, the burden of proof is ‘beyond reasonable doubt’. Given the scientific inaccuracy polygraph testing is not sufficiently probative to be admissible evidence in criminal proceedings.
In the context of family proceedings, the standard of proof is set at a lower level at ‘on the balance of probabilities’. Under the Family Procedure Rules, the family courts have a wide discretion in terms of admissibility of evidence. However, there is no case law precedent to suggest that the family courts are willing to accept polygraph tests as admissible evidence. In the recent case of Re A and B (Children: Restrictions on Parental Responsibility: Extremism and Radicalisation in Private Law)  EWFC 40, at paragraph 74, Ms Justice Russel refused an application for a polygraph test to be used as evidence in family proceedings. Further to this, in the case of Re L (No 2) (A Romanian Child: fact finding & welfare)  EWHC 3191 (Fam), Ms Justice Russel stated “I am told by C that he underwent polygraph tests which exonerated him. Such evidence, and I have not seen the results themselves, is controversial and I can give it no weight.”
On the basis of these recent judgements, the general judicial position is that polygraph tests are not admissible as evidence in family proceedings. The reasoning for this relates to the arguments raised in relation to the admissibility in criminal proceedings in that there is significant scientific uncertainty as to the accuracy of polygraph testing.