This post reviews findings from the Ministry of Justice evaluation of the mandatory polygraph pilot (Gannon TA, Wood JL, Pina A, Vasquez E, Fraser I, The Evaluation of the Mandatory Polygraph Pilot, MoJ Research Series 14/12, July 2012), the peer-reviewed follow-up (Gannon TA et al., Sexual Abuse: A Journal of Research and Treatment, 2014; 26(2):178–203), and Grubin’s comparative review (Polygraph, 2016; 45(2):97–116). Full references appear in the Sources list.

TL;DR

  • A “Clinically Significant Disclosure” (CSD) is new information from an offender that leads to a change in management, supervision, risk assessment, or treatment intervention.[1]
  • 76.5% of offenders in the polygraph group made at least one disclosure, compared with 51.2% in the comparison group; mean disclosures were 2.60 versus 1.25.[2]
  • Actions following CSDs included increasing supervision, informing MAPPA, changing supervision focus, issuing warnings, and recall.[3]
  • Only 25% of probation officers supervising polygraphed offenders believed their offenders were “open and honest,” versus 73% in the comparison group—suggesting polygraph testing recalibrates professional perceptions of risk.[4]
  • Each additional CSD attributable to the polygraph pilot cost an estimated £556.[5]

What Is a Clinically Significant Disclosure?

The concept of a Clinically Significant Disclosure (CSD) is central to the UK evidence base on polygraph-assisted offender management. In the Ministry of Justice evaluation of the mandatory polygraph pilot, Gannon and colleagues defined a CSD as “new information that the offender discloses, which leads to a change in how they are managed, supervised, or risk assessed, or to a change in the treatment intervention that they receive.”[1]

This definition is deliberately operational: it ties the significance of a disclosure not to its content alone but to whether it prompts an observable change in professional practice. A disclosure that reveals, for instance, previously unknown contact with a victim’s family is only classified as clinically significant if the offender manager subsequently adjusts the supervision plan, makes a referral, or takes some other recorded action. This threshold helps guard against inflating disclosure counts with trivial or already-known information.

The CSD framework therefore serves a dual purpose. First, it provides a standardised outcome measure for comparing polygraph-tested and non-polygraph-tested cohorts. Second, it anchors the value of the polygraph examination in its downstream effects on offender management, a point of direct relevance to any assessment conducted under Standards of Practice that emphasise utility and proportionality.

Headline Disclosure Rates

The peer-reviewed analysis by Gannon et al. (2014) reported that offender managers in the pilot polygraph group identified a significantly higher proportion of offenders making at least one CSD: 76.5%, compared with 51.2% in the comparison group.[2] Mean total disclosures per offender were also markedly higher in the polygraph group (M = 2.60) than in the comparison group (M = 1.25).[6]

Importantly, the majority of disclosures made by offenders in the polygraph group were associated with the polygraph session itself, rather than with routine supervision contacts.[7] This suggests that the examination setting—comprising a structured pre-test interview, physiological monitoring, and post-test questioning—provides a distinct mechanism for eliciting information that standard supervision interviews do not routinely capture.

Key Finding

The polygraph group’s disclosure rate was roughly 25 percentage points higher, and mean disclosures were approximately twice those of the comparison group. Most of these disclosures arose during the polygraph session rather than in routine supervision.[2]

Grubin (2016) further contextualised these findings by reference to the earlier voluntary testing trial, in which probation officers reported new disclosures relevant to treatment or supervision in 70% of first tests, compared with 14% of non-polygraphed offenders over the preceding six months.[8] The odds of a polygraphed offender making such a disclosure were 14 times greater than for a non-polygraphed offender.[9]

Actions Following a CSD

Disclosures only matter to public protection if they precipitate action. The MoJ evaluation found that, following a CSD, a higher proportion of offender managers in the polygraph group than in the comparison group took recorded management actions.[10] The categories of action reported were:

  • Increasing supervision or controls, including recall to custody.[10]
  • Informing a third party (e.g. police, social services).[10]
  • Changing supervision focus, for example redirecting offender-manager sessions towards newly identified risk factors.[10]
  • Informing MAPP meeting or processes (Multi-Agency Public Protection Arrangements).[10]
  • Issuing a warning to the offender.[10]

The 2026 HMPPS Polygraph Examinations Policy Framework confirms that this operational pathway remains current: information from polygraph sessions may be shared with police or other agencies where a legal gateway permits, and disclosures suggesting the individual can no longer be safely managed in the community may form the basis for recall.[11] Information sharing with partners may occur under MAPPA or other appropriate arrangements, including under section 14 of the Offender Management Act 2007.[12]

Key Point

“Changing supervision focus” is the action category most directly relevant to treatment planning, because it entails redirecting the content and emphasis of an offender’s supervision programme in response to newly disclosed risk factors.[10]

The Probation Officer Perception Gap

One of the most striking findings concerns how polygraph testing reshaped probation officers’ professional judgements. In the voluntary polygraph pilot evaluation, 73% of interviewed probation officers who supervised non-polygraphed offenders believed their offenders were “open and honest” with them.[4] Among those supervising polygraphed offenders, however, the figure fell to just 25%.[4]

Common Misconception

The 25-versus-73% gap is sometimes cited as evidence that polygraph testing erodes the supervisory relationship. In context, however, the finding may more plausibly indicate that the polygraph process revealed information that challenged previously over-optimistic assessments of offender compliance. Probation officers with access to polygraph-derived disclosures had a richer, and arguably more realistic, picture of offender behaviour.

This perception gap has significant implications for treatment planning. If practitioners supervising non-polygraphed offenders systematically overestimate offender candour, treatment targets may be set on the basis of incomplete information. The recalibration effect observed in the polygraph group suggests that the examination process can surface risk-relevant material that would otherwise remain hidden during routine supervision.

Cost per Additional CSD

The MoJ evaluation estimated that the cost of each additional CSD attributable to the mandatory polygraph pilot was £556.[5] This figure represents a marginal cost: the additional expenditure per CSD above the baseline rate that would have been observed without polygraph testing.

In Numbers

£556 — the estimated cost of each additional Clinically Significant Disclosure generated by the mandatory polygraph pilot.[5]

Whether £556 per additional CSD represents value for money depends on the downstream consequences of the disclosures concerned. A single CSD that leads to the recall of a high-risk offender, or to the identification and safeguarding of a previously unknown victim, may avert harms whose costs far exceed the examination fee. The published evaluations do not, however, include a full cost–benefit analysis that traces individual CSDs through to safeguarding or criminal-justice outcomes.

Honest Gap: Treatment-Programme Integration

Caveat

No open-access evaluation located for this review establishes how polygraph-derived disclosures are integrated with specific accredited HMPPS treatment programmes (e.g. Kaizen, Horizon). The research reviewed here speaks to offender-management integration—changes in supervision, risk assessment, and multi-agency referral—rather than to programme-level treatment integration.

The CSD framework as operationalised by Gannon et al. records that a disclosure may lead to “a change in the treatment intervention that [the offender] receive[s].”[1] However, the evaluations report action categories at the supervision level (increasing controls, changing supervision focus, MAPPA referral, warning, recall) rather than at the level of specific structured treatment programmes. Whether and how disclosures feed into the content of programmes such as Kaizen or Horizon is a question the available evidence does not directly address.

Grubin (2016) similarly frames the benefit of polygraph testing in terms of disclosures “relevant to treatment or supervision,” grouping the two together without disaggregating programme-specific treatment effects.[8] This represents a genuine gap in the UK evidence base. Future research that traces the pathway from CSD to treatment-programme content adjustment would strengthen the case for polygraph testing as a treatment-planning tool, rather than solely an offender-management tool.

Comparison Table: Polygraph vs Comparison Group

Summary of key findings from the mandatory polygraph pilot evaluation
Measure Polygraph group Comparison group Source
Offenders making ≥1 disclosure (%) 76.5% 51.2% Gannon et al. (2014)[2]
Mean total disclosures per offender 2.60 1.25 Gannon et al. (2014)[6]
Probation officers believing offenders “open and honest” (%) 25% 73% Grubin (2016)[4]
Cost per additional CSD £556 (marginal cost attributable to polygraph pilot) Gannon et al. (2012)[5]
Approx. one third of offenders “Deception Indicated” on first test Most notably higher-risk offenders Gannon et al. (2014)[13]

Glossary

CSD — Clinically Significant Disclosure
New information disclosed by an offender that leads to a recorded change in management, supervision, risk assessment, or treatment intervention. The term was operationalised by Gannon et al. (2012) for the MoJ mandatory polygraph pilot.
PCSOT — Post-Conviction Sex Offender Testing
The use of polygraph examinations as part of the supervision and management of convicted sex offenders in the community, typically to monitor compliance with licence conditions and elicit risk-relevant disclosures.
MAPPA — Multi-Agency Public Protection Arrangements
Statutory arrangements under which police, probation, and prison services work together (with other agencies) to assess and manage the risk posed by violent and sexual offenders in England and Wales.
OMA — Offender Management Act 2007
UK legislation that, among other provisions, introduced the statutory basis for mandatory polygraph testing of certain sexual offenders on licence (ss. 28–30).
DAA — Domestic Abuse Act 2021
UK legislation that extended mandatory polygraph testing to certain domestic-abuse perpetrators released on licence (s. 76).
HMPPS — HM Prison and Probation Service
The executive agency of the Ministry of Justice responsible for managing prisons and probation services in England and Wales, and for administering the statutory polygraph regime.
APA — American Polygraph Association
A US-based professional body for polygraph examiners that publishes standards, model policies, and research. Individual UK examiners may hold APA certification, but the APA is not a UK body.
CQT — Comparison Question Test
A polygraph testing format that compares physiological responses to relevant (case-specific) questions with responses to comparison questions designed to elicit a known or expected reaction.
BPS — British Polygraph Society
An unincorporated UK membership body for polygraph professionals, founded in 2017. BPS is not a statutory regulator and has no role in the HMPPS polygraph regime.
Recall
The process by which an offender on licence in the community is returned to custody, typically because of breach of licence conditions or because the offender can no longer be safely managed in the community.
Offender Manager
The probation officer or responsible officer assigned to supervise an offender on licence in the community, including overseeing compliance with licence conditions and coordinating with partner agencies.
DI — Deception Indicated
A polygraph test outcome in which the examiner’s analysis indicates that the examinee’s physiological responses are consistent with deception in response to the relevant questions.

This post is a research summary prepared for informational and educational purposes. It does not constitute legal advice, clinical guidance, or an endorsement of any particular approach to offender management. The statutory polygraph regime in England and Wales is administered by HMPPS under the Offender Management Act 2007 (ss. 28–30) and the Domestic Abuse Act 2021 (s. 76). Readers requiring guidance on specific cases should consult the relevant HMPPS policy framework and their own professional or legal advisers.

Sources

  1. Gannon TA, Wood JL, Pina A, Vasquez E, Fraser I. The Evaluation of the Mandatory Polygraph Pilot. Ministry of Justice Research Series 14/12. London: Ministry of Justice, July 2012. ISBN 978-1-84099-555-8. gov.uk
  2. Gannon TA, Wood JL, Pina A, Tyler N, Barnoux MFL, Vasquez EA. An evaluation of mandatory polygraph testing for sexual offenders in the United Kingdom. Sexual Abuse: A Journal of Research and Treatment. 2014;26(2):178–203. doi:10.1177/1079063213486836. Open-access version (Kent Academic Repository)
  3. Grubin D. Polygraph Testing of Sex Offenders. Polygraph. 2016;45(2):97–116. polygraph.org (PDF)
  4. HM Prison and Probation Service. Polygraph Examinations Policy Framework. Re-issue date 8 January 2026. assets.publishing.service.gov.uk (PDF)
Tags hmpps legislation oma-2007 pcsot standards-of-practice validity
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