Forensic Polygraph & Credibility Assessment

A forensic polygraph examination is a structured, science-based assessment that measures physiological responses — such as cardiovascular activity, respiratory patterns and electrodermal activity — whilst an individual answers a carefully prepared set of questions. Unlike informal "lie detector tests" sometimes portrayed in the media, a forensic polygraph examination follows validated testing protocols and is conducted by a qualified, experienced examiner.

At The Centre for Forensic Neuroscience, every examination is grounded in peer-reviewed methodology and administered by Dr Keith Ashcroft, a chartered forensic psychologist. The process is designed to provide reliable, evidence-based findings that can withstand professional and legal scrutiny.

Polygraph examinations can serve a range of purposes depending on the circumstances. Individuals facing false allegations may use an examination to support their account. Solicitors may instruct an examination to assist with case strategy. Employers may commission testing as part of a workplace investigation. In family and relationship matters, a domestic polygraph can help establish trust or resolve disputes.

Each case is different. During our initial consultation, we assess whether a polygraph examination is appropriate and likely to produce meaningful, actionable results. Not every matter is suited to polygraph testing, and we will advise you honestly.

Not every case is appropriate for polygraph testing. Before accepting an instruction, we conduct an independent suitability assessment to determine whether an examination can be conducted ethically and is likely to yield reliable results. Factors we consider include the nature of the issue, the health and wellbeing of the examinee, and whether clearly defined, testable questions can be formulated.

We decline cases where testing would be inappropriate — for example, where there are certain medical or psychological contraindications. This careful screening process protects both the integrity of the results and the welfare of the individual being tested. To discuss your circumstances, please contact us in confidence.

Peer-reviewed research indicates that professionally conducted polygraph examinations using validated testing formats achieve accuracy rates typically in the region of 80–90%, depending on the specific technique employed and the conditions of the examination. No diagnostic tool — whether medical, psychological or forensic — offers absolute certainty, and responsible practitioners acknowledge this.

Accuracy depends significantly on examiner competence, the quality of question formulation, and adherence to established protocols. We provide a detailed discussion of the evidence base on our polygraph accuracy page. At The Centre for Forensic Neuroscience, we use only validated, peer-reviewed methodologies to maximise the reliability of every examination.

The examination follows a structured, multi-phase process. It begins with a thorough pre-test interview, during which the examiner explains the procedure, discusses the issues to be tested, and reviews every question that will be asked — there are no surprise questions. The examinee then completes a consent form confirming voluntary participation.

During the in-test phase, physiological data is recorded whilst the agreed questions are presented. Following data collection, the charts are analysed using validated scoring methods. A post-test discussion may follow, and a formal report is prepared. You can read a full step-by-step guide on our examination preparation page.

A typical forensic polygraph examination takes between two and three hours in total. This includes the pre-test interview, the in-test data collection phase, and a post-test discussion. The pre-test interview is often the longest component, as it is essential to ensure the examinee understands the process and that the test questions are properly formulated.

We never rush an examination. Adequate time is critical to ensuring the validity and reliability of the results. In more complex cases — for example, those involving multiple issues or solicitor-instructed matters — the process may take longer. We will provide an estimated timeframe when you book your examination.

Polygraph questions must be specific, unambiguous and answerable with a clear "yes" or "no." They are developed collaboratively during the pre-test phase and are always reviewed with the examinee before testing begins. Questions typically focus on whether a specific act occurred or did not occur — for example, "Did you take the item in question?" rather than broad or opinion-based enquiries.

The number of relevant questions is limited by the testing format used, usually between two and four per examination. This constraint is a feature of the methodology, not a limitation — it ensures each question receives sufficient physiological data for reliable analysis. We discuss question design in detail during the booking and preparation process.

Yes. With the exception of certain statutory requirements — such as post-conviction sex offender testing (PCSOT) mandated under the Offender Management Act 2007 — polygraph examinations are voluntary. An individual cannot be compelled to take a test, and informed consent must be obtained before any examination proceeds.

We take the principle of voluntary participation very seriously. Before testing, the examiner confirms that the examinee understands they may withdraw at any point without penalty. If there is any indication that an individual is participating under duress, we will not proceed with the examination.

Confidentiality is fundamental to our practice. All enquiries, consultations and examination results are treated in strict confidence. We comply fully with UK data protection legislation, and our data handling procedures are outlined in our privacy policy.

Examination reports are released only to the instructing party — whether that is the individual examinee, their solicitor, or an authorised representative of an instructing organisation. We do not share results with third parties without explicit written consent, except where we are required to do so by law or where there is a safeguarding concern. Confidentiality arrangements are confirmed in writing before the examination takes place.

Yes. We regularly accept instructions from solicitors, barristers and legal teams across a wide range of practice areas, including criminal defence, family law, employment disputes and regulatory matters. A solicitor-instructed polygraph examination can assist with case preparation, help evaluate a client's account, or provide supporting evidence for submissions.

When instructed by a legal professional, the examination is conducted under the same rigorous protocols as any other case. Reports are prepared to a standard suitable for professional and, where appropriate, judicial consideration. We are experienced in working within the requirements of the legal profession and can provide expert witness testimony if instructed to do so.

Yes. Organisations commission polygraph examinations in connection with corporate misconduct investigations, internal fraud enquiries, breach of contract matters and pre-employment screening for sensitive roles. Testing must be conducted on a voluntary basis and within an appropriate procedural framework.

We work with HR departments, in-house legal teams and external investigators to ensure that polygraph testing is integrated properly into the wider investigation. Our approach prioritises procedural fairness, employee welfare and compliance with employment law. We provide a confidential initial consultation to assess whether polygraph testing is appropriate for your organisation's specific circumstances.

The admissibility of polygraph evidence in UK courts is not straightforward. Polygraph results are not routinely admitted as evidence in criminal proceedings in England and Wales. However, they may be considered in certain contexts — for example, in family court proceedings, employment tribunals, professional disciplinary hearings, or as part of submissions to the Criminal Cases Review Commission.

Even where polygraph results are not formally admitted, they can play a valuable role in case strategy, plea discussions, or supporting an individual's credibility. We prepare all reports to a standard that would withstand judicial scrutiny, and Dr Ashcroft is experienced in providing expert witness testimony when required.

A therapeutic polygraph examination is used in clinical and rehabilitative settings, most commonly as part of treatment programmes for individuals convicted of sexual offences. Under the PCSOT framework (post-conviction sex offender testing), polygraph examinations support the monitoring of licence conditions and help treatment providers assess an individual's compliance and progress.

Therapeutic polygraph can also be used in cases involving sex addiction or compulsive sexual behaviour, where it forms part of a broader therapeutic programme. In these contexts, the examination supports the treatment process rather than serving a purely investigative function. We work closely with therapists and supervising professionals to ensure appropriate integration.

No diagnostic procedure is infallible, and polygraph testing is no exception. It is possible, though uncommon with properly conducted examinations, for a truthful individual to produce a result that indicates deception — what is known as a "false positive." This is one reason why the qualifications and experience of the examiner, and the testing protocol used, are critically important.

At The Centre for Forensic Neuroscience, we take extensive steps to minimise this risk, including thorough pre-test preparation, use of validated testing formats, and careful data analysis. We also recognise that a polygraph result is one piece of evidence and should always be interpreted within the broader context of a case. Read more about polygraph accuracy and error rates.

A "false negative" — where a deceptive individual produces a result that does not indicate deception — is possible but infrequent when examinations are conducted by a competent examiner using validated protocols. Various countermeasure techniques are sometimes discussed online, but trained examiners are specifically skilled in identifying attempts to manipulate the testing process.

This is another reason why choosing a qualified polygraph examiner is essential. The reliability of any examination depends on the examiner's training, experience and adherence to established standards. We are transparent about what polygraph can and cannot do, and we never overstate its capabilities.

Fees depend on the nature and complexity of the case, the location of the examination, and whether additional services — such as expert witness reports or attendance at hearings — are required. We provide a clear, written fee quotation before any commitment is made, so there are no unexpected costs.

We understand that cost is an important consideration. Detailed information about our fee structure, what is included, and how our pricing compares to other providers is available on our polygraph examination costs page. We are always happy to discuss fees during an initial, no-obligation consultation — please get in touch.

Yes. Whilst our primary office is based in Manchester, we conduct examinations across England, Scotland, Wales and Northern Ireland. We regularly travel to clients' premises, solicitors' offices and other suitable locations. For international matters, we have conducted examinations in a number of jurisdictions and can discuss arrangements for cases with an overseas element.

Examinations require a quiet, private room with appropriate conditions. We will advise on venue requirements when you book. Travel fees may apply for locations outside the United Kingdom; these are confirmed in advance as part of your fee quotation. Please contact us to discuss your location requirements.

The Centre for Forensic Neuroscience is led by Dr Keith Ashcroft, a chartered forensic psychologist with extensive experience in polygraph examination, investigative psychology, statement analysis and cyber psychology. Unlike commercial "lie detector" operators, we bring a multidisciplinary forensic science perspective to every case.

We do not accept every case — our independent suitability assessment ensures we only proceed where testing is ethical and likely to produce reliable results. Every examination is conducted personally by Dr Ashcroft, not delegated to junior staff. This combination of academic rigour, clinical experience and ethical commitment is what distinguishes our practice. Learn more about choosing a polygraph examiner.