Polygraph Interviews and Examinations

Forensic & Civil Credibility Assessment

FORMATION: The Centre for Forensic Neuroscience was established in 2002, with our main offices in Liverpool, Edinburgh, Glasgow, Blackpool, and Manchester, and provides both forensic and civil/private credibility assessment services (often referred to as lie detection) internationally.

EXAMINERS: We have the UK’s largest team of dedicated expert credibility assessment examiners, with Dr Keith Ashcroft as the Principal Polygraph Consultant, and he is also a Chartered Investigative Psychologist/Scientist. He is a member in good standing at the National Polygraph Association (USA), the American Association of Police Polygraphists, director member of the  UK Polygraph Association, member of the Society for Psychophysiological Researchas well as the American Polygraph Association. He has been trained at American Polygraph accredited & British Accreditation Council academies, including advanced training at the Backster School of Lie Detection established in 1959, Behavioural Measures UK Polygraph Training Centre operated by Behavioral Measures, as well as the Peak Credibility Assessment Center; All examiners are available for instruction in your location throughout the United Kingdom, Europe, the Middle East and the rest of the world.

We specialise in providing specific issue examinations using only accepted protocols and standards in accordance with the American Polygraph Association and ASTM International (committee E52 on Forensic Psychophysiology). We employ strict quality control procedures, as well as using two examiners to confirm results. Our state-of-the art computerised polygraph systems, such as the Limestone Paragon Acquisition System, have a High Resolution 24 bit Analog to Digital Conversion for superior recording and analysis capability.



Domestic polygraph examinations are those in which the examinee and examination address specific issues that involve the credibility of statements regarding interpersonal behaviour between spouses, live-in partners, non-domiciled marital or intimate partners, children, parents, extended family members and blended family members. This is not a screening process to address suspicions, doubts, etc.; it is for the investigation of an incident that is being disputed. We will only take instructions where all participants are actively engaged in counselling. Please note that the opinions of such examinations are based on the interpretation of the physiological data and are therefore investigatory in nature, and other supporting evidence should be taken into account before any actions are taken.


Providing independent quality control of reviews of polygraph examinations (International).


Provision of training/lectures on polygraph related subjects.


Victim and alleged perpetrator testing in those having legal representation only. Please note that the opinions of such examinations are based on the interpretation of the physiological data and are therefore investigatory in nature, and other supporting evidence should be taken into account before any actions are taken. In cases where polygraph examinations are not feasible, we can employ a Visual Assessment of Sexual Preference.


In legal terms, a child is defined as anyone under the age of 18. Therefore, safeguarding children is about protecting all those under 18 from harm. This can be done by investigating individuals with access to children, either in an employment context or within an intimate or family relationship. 


Polygraph testing for private-sector employees who are under investigation for allegations relating to economic loss to their employers.


Prevention, detection and investigations of insider attacks.


The polygraph is used within a therapeutic setting to assist in disclosure, sobriety and relapses in sex addiction; as well as treatment resistance etc.. We receive referrals from various therapists who offer proven psycho-educational programmes for the treatment of sex and pornography addiction and support programmes for partners. Please note that we cannot be instructed in cases where the partner views a polygraph interview and examination as the only way of regaining trust (there must be additional sources). In addition, there must not be any evidence of punitive/vindictive motives as opposed to therapeutic considerations for seeking a therapeutic polygraph.


We provide polygraph screening testing for Public and Private sector companies, as well as periodic honesty testing, including drug screening. Our services include psychometric testing using the Holden Applicant Screening Measure. The Holden Applicant Reliability Measure was developed by Dr Ronald Holden at Queen’s University and has been further researched by Dr Angela Book at Brock University. This dynamic psychometric instrument provides valuable insights on employment candidates to save resources related to recruitment and training.

PAIRED TESTING (Marin Protocol)

Used in situations where one of two opposing witnesses is most likely being deceptive. Effectively used in mediation contexts.


For identifying concealed assets.


Polygraph testing for those who have been granted leave to Appeal (N.B. ~ in the UK this cannot form the basis of appeal against conviction) (Pro Bono).


Polygraph testing for those alleged acts of misconduct or accused of same.


Polygraph testing of individuals seeking asylum is used to determine the validity of the claims of the petitioner in immigration cases. The statements of the petitioner requesting asylum can be verified by a polygraph test. The results of the test can assist in making an informed decision with regard to granting or withholding asylum.


Forensic / Criminal matters: such as homicide, sexual violence, theft, fraud, sabotage, and espionage. Allegations of sexual abuse are subject to our enhanced service with two forensic polygraph examiners. CFN provides solicitors and lawyers with an assessment as to the credibility of the defendant and witness in criminal matters.


To effectively manage sex offenders in the community. Examinations for Denial – Sexual History – and Maintenance/Monitoring, which is conducted in conjunction with Therapists and Probation Officers.


Polygraph testing to assess the value of critical intelligence sources.


Polygraph testing for sports legal matters (international), as well as Expert Witness Testimony.


Providing expert witness testimony internationally on matters relating to credibility assessment and its related technology.


We have vast experience in collaborating with major film directors such as Oliver Stone for example (Snowden), working internationally.


Frequently Asked Questions: 

How to request an appointment

We strongly advise that you call the examiner personally to discuss the issue and receive an initial consultation. The time and date and the requested location can then be agreed upon. Your call will be followed up by receiving and email with all the respective details and recommendations for the examinee to prepare for the polygraph interview and examination. Please call +44 (0)7790732828.

MUST HAPPEN ON voluntary basis
It is vitally important to stress that all examinations must be taken on a voluntary basis. No person should be intimidated or coerced into taking such an examination. If you have been threatened to participate in a polygraph interview and examination, then this could have a negative influence over the whole testing process. As a strict policy we do not accept instructions where we believe coercion or threats are present.
I am considering an alternative to polygraph - using eye tracking algorithms, is this effective?

This type of technology should never be used in isolation but in conjunction with a traditional polygraph procedure. Ocular-motor measures of deception are susceptible to substance countermeasures, such as intoxicants and stimulants, which substantially reduce accuracy;

Effects of acute alcohol ingestion on eye movements and cognition: A double-blind, placebo-controlled study


In addition, the subject’s reading level also limits its applicability in particular examinees. It should also be noted that neurological conditions would severely disrupt any meaningful decisions on veracity or deception; one person in six in the United Kingdom has such a neurological disorder. Any technology without a ‘human in the loop’ giving a decision, devoid of the added scrutiny of a ‘post-test interview’ must always be viewed with some scepticism.

Fees vary on the type of exam and where it will be conducted. Credibility assessment requires extensive training, continuing professional development, as well as specialised instrumentation, therefore our fees reflect this fact. Our examiners are also qualified as Expert Witnesses. A retainer fee is required on instruction. 
Retainer Fees

Why is a retainer fee required? A significant number of clients fail to show up to their appointments, therefore, this fee covers all the time and effort provided in setting up the procedure (which is non-refundable). In addition, there may be attempts to use the threat of a polygraph examination against the accused; therefore we will not engage with the client until a retainer fee has been paid to mitigate these possible scenarios. 

The retainer fee is “to retain the services of the examiner” at the allocated time and place. 

Various U.S. Government research studies have found that the single-issue (one question) credibility assessments, conducted by an appropriately qualified examiner, are 87 to 95 percent accurate.  It is undeniably the most accurate method for determining truth or deception. Notably the accuracy of multi-question formats is approximately 80 percent due to a number of confounding memory related factors. 
neutral testing environment
Usually we can arrange a suitable neutral testing environment in your particular location to ensure that tests can be conducted in a proper manner. For therapeutic services, our consultants use clinic settings, should this be a necessary requirement. In accordance with APA recommendations, we do not do domestic (home) testing as it is rarely possible to control the environment to a satisfactory degree. 
Failing a polygraph examination
It is vitally important to stress that before any life-changing decisions are made on the basis of a ‘failed’ polygraph examination there must be other corroborating evidence to substantiate the case. 
it takes 2 hours or more

Please also note that the whole process takes around two hours or more to complete. It involves an full interview to determine a statement of the facts, as well as the use of the polygraph instrument to collect data. 

single & specific issues question formats

Single-Issue and Specific-Issue Polygraph Examinations have proven the most accurate examinations available to the polygraph profession.

Single-Issue Polygraph Examinations focus specific questions on the examinee’s recall of the events, like the circumstances associated with an armed robbery. Thus, questions of this type, for example, might focus on different facets of the event, i.e., taking money from the bank, pointing a weapon at the bank staff, and possibly driving the getaway car. All these target questions revolve around a Single-Issue or Event.

A Specific-Issue Polygraph Examination differs slightly from a Single-Issue Examination in that the questions focus on only one or single behaviour of the alleged conduct. For example, did the examinee point a gun at the bank staff?

Furthermore, the answer to each question is limited to ‘yes’ or ‘no’. Ideal questions must be: Concise, be understandable to the examinee, not be presumptive of guilt, not test for hypothetical intentions, or about future behaviours or state of mind, or ask for an opinion, and lastly, legalisms, as well as medical/diagnostic terms, should be avoided. In addition, one should never test for more than one issue per relevant question and address primary details rather than tertiary facts. 

The primary relevant questions must specify the action or behaviour as closely as the recalled mental image of the investigated issue.  


Any additional issue must be done with a separate polygraph test. Examinees will be sent information on how to prepare for the test and be evaluated for suitability according to various criteria; such as for example:

  • Be free of any serious illness.
  • The examinee should not have been subjected to any accusatory interviews prior to the examination.
  • The examinee must not be under the influence of alcohol or substances of abuse at the time of the test.
  • The examinee must have had a reasonable amount of sleep prior to the test.
  • The examinee must be sufficiently hydrated and had something to eat prior to the test.
  • At least one finger or thumb must be nail varnish/or false nail – free to ensure that the blood oxygen levels can be accurately determined. 
  • COVID 19: Please inform the examiner prior to your appointment if you have symptoms of a loss of taste or smell, a persistent cough, fever, a headache plus fatigue; as well as if any close contact is self-isolating due to COVID 19. 
It should be noted that there are certain limitations of polygraph testing:

      • The test results relate to what the examinee perceives.
      • Not everyone is suitable for testing due to individual physiological and psychological differences and states.
      • The clarity of issues being tested.
      • Number of issues being tested.
Our examiners work in conjunction with specially trained interpreters to provide polygraph tests in most languages. They are also trained in cross-cultural sensitivities in order to engage more effectively with people from different cultures.

Please note that our examiners do not re-examine the work of other polygraph examiners as a matter of company policy and professional ethics unless there is a clear violation of the American Polygraph Association standards of practice.

In most cases the results are given during the examination process, or, soon thereafter if a peer review is necessary. Our examiners will at all times ensure complete confidentiality and discretion. 
The examinee must provide government identification (Photo ID Card, Passport, Driving License ) on arrival for verification purposes.
How many Questions can be asked?

Given the ubiquity of television programmes showing so-called ‘Lie Detector Tests’ it is expected that the polygraph examiner can ask multiple questions on various issues; this is simply not possible in scientific terms.  In formal, valid credibility assessment, only one issue is addressed within the examination to ensure accuracy. You cannot mix issues within the same polygraph interview and examination.

How does the polygraph instrument work?

How the polygraph instrument identifies the particular arousal pattern for each channel, as it relates to the determination of truth or deception, does not rely on fight, freeze or flight i.e. threat of punishment, consequences of being caught lying or even psychological set. Nor is it a conditioned response, or related to anxiety (there is no basis in research for this). These notions are outdated and irrelevant to modern polygraph science. Current understanding refers to what is known as the ‘orienting response’ to novel or important stimuli, which are intrinsically related to experiences in autobiographical memory, emotional salience and the act of lying requiring increased cognitive processing. Specifically, it takes more cognitive activity to lie than to tell the truth because you need to construct a narrative, so the degree of cognitive processing can be relevant in determining deception. This collection of underlying neural processes give rise to increased autonomic arousal that is routinely detected by the polygraph instrument. Thus, essentially, we are analyzing the strength of attention as determined by autonomic arousal.

How much does it cost - fees?

Our fees depend on the complexity of the investigation and the disbursements for travel and serviced offices, where necessary. The standard fee that will be quoted is for the polygraph interview and examination, plus a verbal report. 

Who can be present?

Only the examiner and the examinee can be present when the actual polygraph interview and examination takes place. As recommended by the American Polygraph Association, which ensures the whole process can be conducted in a controlled environment. 

Home Environment Examinations

In accordance with the American Polygraph Association recommendations and good practice, we do not conduct tests in a home environment.