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Paired Polygraph Testing for Conflicting Accounts

When two individuals provide contradictory accounts of the same event, independent polygraph examinations may provide additional investigative information to assist decision-makers.

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Paired polygraph testing for conflicting accounts — independent examinations by The Centre for Forensic Neuroscience

What Is Paired Polygraph Testing?

Paired polygraph testing is a structured approach used when two individuals provide conflicting accounts of the same event and the factual truth of those accounts cannot readily be established by other means. Rather than relying upon a single examination in isolation, paired testing involves conducting independent polygraph examinations of each party, with each assessment carried out separately and objectively.

The approach has its origins in professional polygraph practice within the United States, where it has been applied in a range of investigative, civil, and domestic contexts. The methodology is sometimes referred to as the Marin Protocol, named after the structured framework developed to guide examiners in conducting these paired assessments in a fair and systematic manner.

The fundamental principle is straightforward: where two accounts of the same event are mutually exclusive—that is, both cannot simultaneously be true—independently examining each party under standardised conditions may yield additional information that assists those responsible for evaluating the competing claims. The outcomes of each examination are then compared objectively, providing an additional layer of investigative data.

It is essential to understand that paired testing does not determine guilt or innocence. It does not replace investigation, nor does it constitute proof. It is one source of information among many, and its results must always be interpreted alongside all other available evidence.

When Might Paired Testing Be Considered?

Paired testing may be appropriate in a variety of circumstances where conflicting accounts require independent assessment.

Historical Allegations

Contested accounts of events that occurred in the past where contemporaneous evidence may be limited.

Workplace Disputes

Internal matters involving conflicting employee accounts of misconduct, harassment, or other workplace incidents.

Civil Disputes

Contested factual matters in civil litigation where credibility is a central issue.

Internal Investigations

Organisational inquiries where competing accounts hinder effective resolution.

Safeguarding Concerns

Matters involving the welfare of children or vulnerable adults where accounts differ materially.

Witness Credibility

Disputes where the credibility of witnesses is central to establishing the facts of an event.

Theft & Fraud

Allegations of theft, fraud, or financial misconduct where the parties provide contradictory accounts.

Relationship Disputes

Domestic and interpersonal disputes where contested facts require independent assessment.

Important: The suitability of paired testing must be assessed individually in every case. Not all disputes are amenable to polygraph examination, and The Centre for Forensic Neuroscience reserves the right to decline instructions where testing would be inappropriate, unethical, or unlikely to produce meaningful results.

How the Process Works

1

Initial Consultation

A confidential discussion to understand the circumstances, the nature of the conflicting accounts, and to determine whether paired testing may be appropriate.

2

Case Review

A detailed review of the available information, including the specific accounts provided by each party, relevant documentation, and any contextual background material.

3

Examiner Allocation

Wherever possible, separate examiners are allocated to conduct each independent examination, ensuring objectivity and eliminating the risk of cross-contamination between assessments.

4

Independent Examinations

Each party undergoes a separate polygraph examination conducted under standardised conditions, with validated testing techniques appropriate to the specific issue under examination.

5

Analysis and Quality Review

The physiological data from each examination is analysed independently. Where appropriate, quality assurance and peer review are conducted to provide an additional layer of professional oversight.

6

Reporting

Each examiner produces an independent report documenting their findings. The reports are then provided to the instructing party alongside any quality review documentation.

Why Separate Examiners Matter

The integrity of paired testing depends upon each examination being conducted with genuine independence. Using separate examiners wherever practicable is a cornerstone of this approach and serves several important functions.

Independence

Each examiner approaches their assessment without knowledge of the other party’s physiological responses, ensuring that conclusions are reached entirely on their own merits.

Reduction of Bias

When a single examiner tests both parties, there is a natural risk—however unconscious—that impressions from one examination may influence the conduct or interpretation of the other. Separate examiners mitigate this risk.

Objective Assessment

Separate examiners ensure that the analysis of physiological data from each examination is conducted without any reference point from the opposing party’s test.

Professional Safeguards

The use of separate examiners represents a professional safeguard that enhances the overall credibility and defensibility of the testing process.

Confidence in the Process

All parties—including the individuals being tested, instructing solicitors, and other stakeholders—may have greater confidence that the process has been conducted with rigour and impartiality.

Understanding Accuracy and Confidence

The reliability of any polygraph examination depends upon several interrelated factors, including the use of validated testing techniques, the competence and training of the examiner, the suitability of the examinee, and the clarity of the issue being tested.

In paired testing, confidence in the overall assessment may be strengthened when both examinations are conducted independently using validated methods and the results are consistent with one another. Where one party’s results indicate significant physiological responses associated with deception whilst the other party’s results are consistent with truthfulness, this convergence of findings may provide meaningful investigative information.

However, it is important to acknowledge that polygraph examinations are not infallible. Results may be inconclusive. External factors may affect physiological responses. Individual differences exist in autonomic reactivity.

“Polygraph examinations are probabilistic assessments rather than determinations of fact.”

Validated testing techniques form the scientific foundation of each examination

Examiner competence and adherence to professional standards are essential

Independent assessments reduce the potential for examiner bias

Confidence may increase when conflicting accounts are examined separately and converging findings emerge

Appropriate and Inappropriate Uses

Appropriate Uses

  • ✓ Investigative support and information gathering
  • ✓ Credibility assessment of competing accounts
  • ✓ Disputed factual accounts requiring independent evaluation
  • ✓ Statement verification in contested matters
  • ✓ Civil disputes where credibility is a central issue
  • ✓ Internal investigations with conflicting witness accounts

Not Appropriate

  • ✗ Determining guilt or innocence
  • ✗ Replacing evidence or investigation
  • ✗ Coercive or punitive use against any party
  • ✗ Testing vulnerable individuals without prior suitability assessment
  • ✗ Situations where voluntary participation is absent
  • ✗ Substituting for proper legal or investigative process

Safeguards and Ethical Standards

The Centre for Forensic Neuroscience adheres to rigorous professional standards to ensure the integrity and fairness of every paired testing engagement.

Informed Consent

Each examinee receives a full explanation of the process and provides written consent prior to examination.

Suitability Screening

Every examinee is assessed for physical and psychological suitability before testing proceeds.

Professional Standards

All examinations are conducted in accordance with recognised professional and ethical standards.

Audio-Video Recording

Examinations are recorded for transparency, quality assurance, and professional accountability.

Validated Methods

Only testing techniques that have been validated through peer-reviewed research are employed.

Impartiality

Examiners maintain strict impartiality and do not advocate for any party to the dispute.

Documentation & Retention

Comprehensive records are maintained in accordance with data protection requirements and professional standards.

Independent Review

Where appropriate, independent peer review provides an additional safeguard and quality assurance measure.

Confidentiality

All information is treated with the strictest confidence and handled in accordance with applicable data protection law.

Use by Solicitors and Barristers

Legal representatives may find paired polygraph testing a useful investigative tool at various stages of case preparation and assessment.

Evaluate Competing Accounts

Assess the relative credibility of contradictory accounts provided by different parties to inform case strategy.

Identify Investigative Leads

Use examination outcomes to guide the direction of further factual investigation and evidence gathering.

Assess Credibility Issues

Obtain additional information to assist in assessing the strength and weaknesses of witness and party credibility.

Support Case Preparation

Incorporate polygraph findings as an additional source of information during the preparation and evaluation of a case.

Facilitate Informed Decisions

Provide clients and instructing parties with additional data to support informed decision-making about how to proceed.

Note: The Centre for Forensic Neuroscience does not suggest that paired polygraph testing results will be admissible at trial. The value of paired testing in the legal context lies in its investigative and preparatory utility rather than its evidential status.

Frequently Asked Questions

No. Paired testing does not determine guilt or innocence. Polygraph examinations are probabilistic assessments that may indicate the presence or absence of significant physiological responses associated with deception. Results should be considered alongside all other available evidence as one source of investigative information. No life-changing decisions should be made solely on the basis of polygraph results.
Whilst it is technically possible for a single examiner to test both parties, it is strongly recommended that separate examiners conduct the independent examinations wherever practicable. Using different examiners reduces the risk of examiner bias, reinforces the objectivity of the process, and maintains confidence in the independence of each examination. Where separate examiners are not available, additional safeguards—such as independent quality review—should be implemented.
In the United Kingdom, polygraph evidence is generally not admissible as evidence of truth at criminal trial. However, polygraph examinations may assist solicitors, investigators, employers, and other parties in assessing credibility, guiding investigations, and informing decision-making within the investigative and preparatory phases of a matter. Any conclusions remain investigative opinions rather than determinations of fact.
Inconclusive results may occur when the physiological data collected during an examination does not meet the threshold for a definitive professional opinion. This is an inherent feature of any diagnostic process. In such cases, additional examination may be considered if appropriate, or the results may simply be reported as inconclusive. An inconclusive outcome does not imply deception or truthfulness. The Centre for Forensic Neuroscience will advise on available options in such circumstances.
Yes. Participation in any polygraph examination must always be entirely voluntary. No individual should be coerced, pressured, threatened, or otherwise compelled to undergo a polygraph examination. The Centre for Forensic Neuroscience will not accept instructions where there is any indication that participation is not voluntary or that coercion or duress has been applied.
Yes. Witnesses who provide specific factual accounts that can be formulated into testable polygraph questions may be examined, subject to individual suitability assessment. This may be particularly relevant in cases where witness credibility is central to the matter under investigation. As with all examinations, participation must be voluntary and the witness must be assessed as suitable for testing.
Each individual polygraph examination typically takes approximately two hours, including a comprehensive pre-test interview. The overall paired testing process—incorporating initial consultation, case review, examiner allocation, independent examinations, quality review, and reporting—may span several days or longer depending on scheduling requirements, examiner availability, and the complexity of the case.
Each examiner produces an independent written report documenting the examination procedure, the questions asked, the physiological data collected, and their professional opinion. Reports are provided to the instructing party in accordance with the agreed terms of engagement. Where quality review or peer review has been conducted, this is documented separately and made available alongside the primary examination reports.

A Decision-Support Tool, Not Proof

Paired polygraph testing provides a structured, objective methodology for independently examining individuals who present conflicting accounts of the same event. By conducting each examination separately—ideally using different examiners—the process maximises independence, reduces the potential for bias, and may provide meaningful investigative information that would otherwise be unavailable.

The value of paired testing lies not in replacing investigation or determining guilt, but in offering an additional source of carefully obtained information that may assist decision-makers in evaluating competing accounts. As with all polygraph examinations, results should be considered alongside the totality of available evidence.

The Centre for Forensic Neuroscience is committed to conducting all examinations in accordance with the highest professional and ethical standards, ensuring that every paired testing engagement is fair, independent, and methodologically sound.

Discuss Whether Paired Testing May Be Suitable

If you are a solicitor, investigator, employer, or private individual facing conflicting accounts that require independent assessment, The Centre for Forensic Neuroscience welcomes confidential enquiries to discuss whether paired polygraph testing may be appropriate for your circumstances.

Book a Consultation

All enquiries are treated with the strictest confidence.