A number of variables may influence the outcome of the polygraph. For example, it has been suggested that the very manner and tone of the questioning can affect polygraph outcomes (Horvath et al., 2013). Comparison of different questioning approaches reveal substantial variation that may affect examination outcomes (Abrams, 1989). For this reason, guidelines for polygraph testing have encouraged standardization of method among examiners (Kokish, 2004). The varying expertise and competencies between examiners (both with regard to polygraph testing and the assessment of sexual offenders) may also influence the validity of the test (Matte, 2012) with accuracy rates varying between 50% and 95% (Rosky, 2012).
A number of within-individual client variables can influence the outcome of polygraph examinations. These include factors both beyond the offender’s control (e.g. learning difficulties, mental illness, medical conditions) and those deliberately induced (e.g. refusal to comply with the examiner’s instruction/ not complying with instructions to answer quickly, or asking that a question be repeated, and intoxication; Lundell & Holmes, 1993). For example, Tanner (2007) noted that patients with dementia may be more prone to confabulation, and perhaps believing in the reality they have constructed, would be unlikely to exhibit physiological signs indicative of deception, rendering polygraph results amongst this population questionable. The mandatory polygraph from Gannon et al.’s (2014) pilot study attempted to match the comparison and the polygraph groups as closely as possible according to the rural/urban constitution of the health trust and client demographics such as age and ethnicity, However, it was shown that the polygraph’s impact on the number of disclosures did not vary by offender demographics (risk as measured RM2000 and index offence type) or experience of sexual offender treatment. One should be mindful that this study was not piloted on under-represented demographic groups, such as female sex offenders.
Polygraph examinees may use countermeasures to purposefully mislead a polygraph test, potentially resulting in false negative results. Innocent individuals may also use countermeasures as an additional safety tactic to try and avoid any possibility of arriving at a deceptive outcome. In studies that have trained offenders in the deliberate use of counter measures, guilty examinees have been successful in faking honesty (Honts et al., 1996). Polygraph countermeasures can be both physical and mental, the former commonly including muscle control (e.g. pressing toes to the floor; clenching buttocks), and pain infliction (e.g. tongue biting). Mental countermeasures involve examinees deliberately attempting to conceal deceptive responses through mental distraction techniques (e.g. creating exciting memories to create enhanced responding to control questions). It is often assumed that mental countermeasures are more detrimental to polygraph validity because these are more difficult to detect; however some research has found no significant differences between the effectiveness of these techniques (Ben-Shakhar 2008; London Daily Telegraph, 2012). Polygraph advocates accept that although the approach should not be used in isolation, as some offenders may be able to fool the test, it is likely that a larger proportion are often successful in fooling their therapists and supervisors. This can
be noted by the higher number of risk assessments employed by probation officers when polygraphy is also used (Grubin, 2010).
PCSOTs can be administered at regular intervals to monitor ongoing compliance amongst offenders. As a result, concern has been expressed that repeated testing may result in ‘practice effects’ which facilitate the rehearsal of a lie, and act as a load-reduction strategy to alleviate physiological arousal associated with anxiety - a primary indicator of deception during the test (Walczyk et al., 2013). Continued exposure to this procedure may also serve to habituate offenders to stressful situations (Branaman & Gallagher, 2005). To alleviate these risks, proponents of the PCSOT suggest that using different polygraph examiners to conduct the tests could reduce habituation effects, though, of course, this will not reduce habituation to the testing procedure itself (Branaman & Gallagher, 2005). Given a standardised form of administration, it is unclear whether using different examiners would have any significant impact on the validity of test outcomes, or whether continued exposure to questioning and discussing one’s crimes serves to desensitize the individual’s emotional connection to their offence.
If polygraph examiners suspect or detect the use of countermeasures during their investigation they will often confront the examinee, and make note of these potential attempts to sabotage the polygraph in their records. It is crucial to fair and accurate testing that examiners should be careful not to draw firm conclusions from a test where countermeasures may have disturbed the validity of the polygraph reading (particularly when these suspicions are confirmed by a second examiner in a quality assurance review). It has been suggested that skilled examiners can detect the use of countermeasures by observing the examinee’s movement (using movement sensors), and identifying distinct physiological profiles indicative of specific countermeasures (Barland, 2003). This can enable them to discount particular polygraph readings, and have greater confidence in the validity of their conclusions. However, according to Heil and English (2009) a proportion of administrators, particularly supervisory officers and treatment providers, lack the necessary skills and proficiency to accurately conduct the PCSOT.
Grubin (2008) accepts that while it is possible for guilty offenders to be familiar with techniques that can assist them to pass the polygraph, in order to use countermeasures effectively, offenders require feedback from their polygraph examiner. The examiner’s competence is dictated by their level of training, skill, and ability to ensure that physiological reactions are produced because of deception rather than by other potential causes of autonomic arousal. This requires well-constructed quality assurance and control programmes (Grubin, 2016). However, with continuous advances in technology it is now possible for members of the public to simply download one of a number of polygraph apps for free onto an electronic device upon which they can practise countermeasures at their leisure. Software applications such as this could arguably jeopardise the integrity of the practice and provide a platform for individuals to discuss the most effective strategies to evade deception detection.