Inconclusive Polygraph Results: What They Mean & What To Do

What Does “Inconclusive” Actually Mean in Polygraph Testing?

When a polygraph examination produces an inconclusive result, it means the examiner was unable to render a definitive opinion about whether the examinee was truthful or deceptive. The physiological data recorded during the examination fell into a range that does not clearly support either determination. In professional polygraph terminology, this is sometimes referred to as “No Opinion” (NO) or “No Determination” (ND).

It is critical to understand that an inconclusive result is fundamentally different from a “deception indicated” (DI) finding. Many examinees, employers, attorneys, and even some law enforcement professionals mistakenly conflate the two, but they represent entirely different analytical outcomes. An inconclusive result simply means the data was insufficient or ambiguous — it does not suggest the person was lying.

The Three Possible Polygraph Outcomes

Every polygraph examination produces one of three possible results. Understanding all three helps put the inconclusive outcome in proper context:

• No Deception Indicated (NDI) — The examinee’s physiological responses to comparison questions were consistently greater than their responses to relevant questions, indicating the person was likely truthful.
• Deception Indicated (DI) — The examinee’s physiological responses to relevant questions were consistently greater than their responses to comparison questions, suggesting the person may have been deceptive.
• Inconclusive / No Opinion (INC/NO) — The difference between responses to relevant and comparison questions was not significant enough in either direction to support a definitive determination.

As explained in our guide on how to read polygraph test results, the scoring process involves analyzing multiple physiological channels across multiple chart collections. When the cumulative scores fall within a narrow band around zero, the result is deemed inconclusive.

Why “Inconclusive” Is Not a Euphemism for Failure

One of the most damaging misconceptions about polygraph testing is the belief that an inconclusive result is essentially a “soft failure.” This misunderstanding can cause unnecessary distress and has real consequences in employment, legal, and personal contexts. The American Polygraph Association (APA) and other professional bodies are clear: an inconclusive result means the data does not support a conclusion in either direction.

Consider an analogy: if a medical test for a particular condition comes back inconclusive, doctors do not diagnose the patient with that condition. Instead, they recommend further testing or alternative diagnostic approaches. The same logic applies to polygraph examinations. For a broader look at common misconceptions, see our guide on 10 misconceptions about polygraph exams.

How Polygraph Scoring Leads to Inconclusive Results

To understand why inconclusive results occur, it helps to understand how a polygraph works at the scoring level. Modern polygraph examinations use numerical scoring systems that evaluate physiological responses across multiple data channels and multiple chart presentations.

The Numerical Scoring System

During a standard polygraph examination, the examiner collects a minimum of three charts (though many examiners collect four or more). For each chart, the examiner compares the examinee’s physiological reactions to relevant questions against their reactions to comparison (or “control”) questions. Each comparison yields a numerical score, typically on a scale from -3 to +3:

• Positive scores (+1, +2, +3) indicate the comparison question produced a greater physiological response than the relevant question (suggestive of truthfulness).
• Negative scores (-1, -2, -3) indicate the relevant question produced a greater response than the comparison question (suggestive of deception).
• A score of zero (0) indicates no meaningful difference between the two responses.

These individual scores are summed across all questions and all charts to produce a grand total. This grand total is then compared against established cutoff scores. The numerical scoring system in polygraph testing uses specific thresholds that define whether the total falls into the truthful, deceptive, or inconclusive range.

The Inconclusive Band

The inconclusive zone exists as a statistical buffer between the truthful and deceptive cutoff scores. For example, in many validated scoring systems:

The width of the inconclusive band varies depending on the specific test format being used. Some polygraph techniques, such as the Zone Comparison Test (ZCT), have well-established cutoff criteria, while others like the Matte Quadri-Track Zone Comparison Test (MQTZCT) use different scoring approaches.

Both manual (human) scoring and automated (computer) scoring can produce inconclusive results. In some cases, the manual and automated scores may disagree — one producing a definitive result while the other yields inconclusive. When this happens, examiners and quality assurance reviewers must carefully evaluate the data to determine the appropriate final call. Our resource on cross-platform polygraph scoring explores this topic in detail.

Physiological and Medical Causes of Inconclusive Results

The polygraph measures physiological responses — changes in respiration, electrodermal activity (skin conductance), and cardiovascular activity. Any condition that disrupts or alters these baseline physiological patterns can make it difficult for the instrument to detect meaningful differences between reactions to relevant and comparison questions.

Cardiovascular Conditions

The cardio channel is one of the most important components of the polygraph. Conditions that affect heart rate and blood pressure can significantly impact test results:

• High blood pressure (hypertension) — Can produce elevated baseline readings that compress the range of detectable changes.
• Arrhythmias — Irregular heartbeats create artifacts in the cardiovascular tracing that can obscure genuine responses.
• Heart disease — Various cardiac conditions alter the cardiovascular response pattern. Read more in our guide on heart conditions and polygraph testing.

Blood pressure medications, particularly beta-blockers, can dampen sympathetic nervous system activity. Since the polygraph fundamentally measures sympathetic arousal, these medications can reduce the magnitude of all physiological responses, making it harder to distinguish between reactions to different question types.

Respiratory Conditions

Pneumograph (respiratory) data is critical for accurate polygraph scoring. Conditions that affect breathing patterns include:

• Asthma — Can cause irregular breathing patterns and may require inhaler use during the examination.
• COPD (Chronic Obstructive Pulmonary Disease) — Produces consistently abnormal respiratory patterns.
• Sleep apnea — Can cause fatigue-related breathing irregularities during the exam. Learn more about sleep deprivation and polygraph testing.
• Allergies and congestion — Even temporary nasal or chest congestion can affect breathing regularity.

Metabolic and Endocrine Conditions

Conditions that affect the body’s metabolic processes can alter physiological baselines:

• Diabetes — Unstable blood sugar levels can cause sweating, trembling, and altered autonomic responses. Our article on diabetes and polygraph testing covers this in depth.
• Thyroid disorders — Both hyperthyroidism and hypothyroidism can affect heart rate, sweating, and nervous system activity. See our guide on thyroid disorders and polygraph test accuracy.
• Hormonal fluctuations — Including those related to pregnancy, menstrual cycle, or menopause. Our article on menopause and polygraph testing provides relevant detail.

Chronic Pain

Chronic pain conditions present a unique challenge for polygraph testing. Constant pain signals can elevate baseline sympathetic nervous system activity, reducing the relative magnitude of deception-related responses. Additionally, pain can cause involuntary movements and muscle tension that create artifacts in the data. For a detailed examination of this issue, see our guide on chronic pain and polygraph exams.

Mental Health Conditions

Various psychological and psychiatric conditions can contribute to inconclusive results:

• Generalized Anxiety Disorder (GAD) — Produces chronically elevated arousal levels across all physiological channels, making it difficult to identify question-specific responses. See our comprehensive guide on anxiety disorders and polygraph testing.
• ADHD — Attention deficits can make it difficult for the examinee to focus consistently on test questions. Our guide on ADHD and polygraph testing provides detailed information.
• Bipolar disorder — Depending on whether the individual is in a manic or depressive phase, physiological baselines can be significantly altered. Learn more about bipolar disorder and polygraph tests.
• PTSD — Can cause hyperarousal, especially if test questions are related to traumatic experiences. Read our guide on PTSD and polygraph testing.

Medications That Affect Results

Numerous medications can influence the physiological channels measured during polygraph testing. A comprehensive discussion is available in our article on medications that affect polygraph test results. Key medication categories include:

• Beta-blockers — Suppress heart rate and blood pressure responses.
• Benzodiazepines (anti-anxiety drugs) — Can dampen overall autonomic nervous system reactivity.
• Antidepressants (SSRIs, SNRIs) — May alter electrodermal activity.
• Antihistamines — Can affect skin conductance and cause drowsiness.
• Stimulants (ADHD medications) — May elevate baseline arousal levels.

Temporary Physical Conditions

Even temporary conditions can produce inconclusive results. As discussed in our article about how temporary illness affects polygraph accuracy, conditions like the common cold, flu, hangovers, or even significant fatigue from sleep deprivation can alter physiological responses enough to prevent a definitive determination.

Technical and Procedural Factors

Even when the examinee is in good physical and mental health, technical and procedural issues during the examination can lead to inconclusive results.

Equipment Issues

Modern polygraph instruments from reputable polygraph manufacturers are generally reliable, but equipment problems can occur:

• Faulty sensors — Malfunctioning galvanic skin response (GSR) electrodes, loose pneumograph tubes, or poorly calibrated blood pressure cuffs can produce unreliable data.
• Improper sensor placement — If sensors are not positioned correctly, the data collected may not accurately reflect the examinee’s physiological state.
• Software glitches — Digital polygraph systems can experience software errors that affect data recording or automated scoring algorithms.
• Environmental interference — Electrical interference, vibrations, or temperature fluctuations can introduce noise into the data.

Question Formulation Problems

The quality of test questions is one of the most critical factors in producing reliable results. Poorly constructed questions can lead to inconclusive outcomes in several ways:

• Ambiguous wording — If a relevant question can be interpreted in multiple ways, the examinee’s physiological response may reflect confusion rather than truth or deception.
• Overly broad questions — Questions that cover too much territory can trigger mixed physiological responses.
• Comparison question failures — If comparison questions do not adequately engage the examinee, the contrast between comparison and relevant question reactions may be insufficient for scoring.
• Too many relevant questions — Overloading a single examination with too many relevant issues can dilute the physiological contrast needed for clear scoring.

Our guide on crafting questions for lie detector tests provides detailed best-practice guidance on question formulation.

Test Duration and Fatigue

A standard polygraph examination takes approximately two to four hours including the pre-test interview, data collection, and post-test phase. Examinations that run significantly longer can produce fatigue effects:

• Physiological habituation — Over time, the body’s autonomic responses can become muted as the examinee habituates to the testing procedure.
• Cognitive fatigue — Mental exhaustion reduces the examinee’s ability to focus on questions and process them consistently.
• Physical discomfort — Sitting in one position with sensors attached for extended periods can cause discomfort that adds noise to the physiological data.

Examiner-Related Causes of Inconclusive Results

The skill, experience, and professionalism of the polygraph examiner play a substantial role in the quality and reliability of test outcomes. Examiner-related factors that can contribute to inconclusive results include:

Inadequate Pre-Test Interview

The pre-test interview is arguably the most important phase of the polygraph examination. During this phase, the examiner establishes rapport, reviews all test questions with the examinee, identifies potential medical or psychological contraindications, and ensures the examinee fully understands each question. A rushed or poorly conducted pre-test interview can lead to:

• Unidentified medical conditions that affect physiological responses
• Examinees who don’t fully understand the questions being asked
• Comparison questions that are not properly developed
• Elevated baseline anxiety due to unresolved concerns about the process

Scoring Errors and Inexperience

Manual scoring requires significant training and experience. An examiner who is new to the profession or who has not maintained their skills through continuing education may:

• Misidentify physiological responses in the data
• Apply incorrect scoring criteria for the test format being used
• Fail to recognize artifacts (non-relevant physiological changes) in the data
• Improperly evaluate the overall quality of the data collection

Examiner Bias

Research has shown that examiner bias — pre-existing beliefs about the examinee’s truthfulness or deception — can subtly influence the testing process. This can occur through:

• Leading behavior during the pre-test interview
• Unconscious changes in question delivery (tone, pace, emphasis)
• Biased scoring decisions, particularly when data is borderline
• Inappropriate reliance on behavioral observations rather than physiological data

This is one reason why our standards of practice emphasize the importance of objective, data-driven scoring and quality assurance protocols.

Environmental and External Factors

The testing environment can significantly influence the quality of polygraph data. Ideal conditions require a quiet, temperature-controlled room with minimal distractions. Factors that can compromise the testing environment include:

Physical Environment

• Noise — Sudden sounds (phones ringing, construction noise, people talking in adjacent rooms) can cause startle responses that contaminate the data.
• Temperature extremes — Being too hot or too cold affects sweating (electrodermal activity) and cardiovascular responses.
• Uncomfortable seating — Physical discomfort can produce physiological responses that are unrelated to the test questions.
• Lighting — Harsh or flickering lighting can cause eye strain and headaches, both of which affect physiological baselines.

It is worth noting that polygraph testing at home or in non-standard locations can increase the risk of environmental interference. Professional testing should always be conducted in a suitable, controlled environment.

Language and Communication Barriers

If the examinee does not fully understand the language in which the test is being conducted, their physiological responses may reflect the cognitive load of translation rather than reactions to the substantive content of the questions. Even examinees who are generally proficient in the test language may struggle with nuanced or technical question wording.

External Stressors

Major life stressors occurring around the time of the examination can elevate baseline arousal and produce erratic physiological patterns:

• Recent bereavement or major loss
• Ongoing legal proceedings unrelated to the polygraph
• Severe financial stress
• Relationship crises
• Work-related pressures

Legal Implications of Inconclusive Polygraph Results

The legal status of polygraph results varies significantly by jurisdiction, and inconclusive results add another layer of complexity. Understanding the legal landscape is essential for anyone facing an inconclusive outcome in a legal context.

Admissibility in Court

In the United States, polygraph results are generally inadmissible in court under the Daubert standard (federal courts) or its state equivalents. However, there are important exceptions:

• Stipulated admissibility — In some jurisdictions, both parties can agree in advance to admit polygraph results as evidence. An inconclusive result in this context would typically not support either party’s position.
• Defense use — Some courts allow defendants to present polygraph results as part of their defense strategy. An inconclusive result is generally unhelpful in this context. For more on this topic, see our guide on polygraph in criminal defense strategy.
• Plea negotiations — Polygraph results frequently influence plea bargaining discussions, even when they are not formally admissible. Our article on polygraph in plea bargaining explores this dynamic.

Post-Conviction Supervision (PCSOT)

In post-conviction sex offender testing (PCSOT), inconclusive results have specific implications. The role of polygraph testing in post-conviction supervision is well-established, and most PCSOT protocols address how to handle inconclusive outcomes:

• Inconclusive results typically require a retest within a specified timeframe
• They do not constitute a “violation” in most supervision frameworks
• Treatment providers may use the inconclusive result as a topic for therapeutic discussion
• Multiple consecutive inconclusive results may trigger a review of the testing protocol

Family Court and Civil Proceedings

In family court and civil litigation, the impact of an inconclusive result depends heavily on the jurisdiction and the specific circumstances. Resources on polygraph results in family court and polygraph testing in civil litigation provide jurisdiction-specific guidance.

Canadian Legal Context

In Canada, the legal landscape around polygraph testing differs from the United States. For Canadian examinees, our guide on polygraph testing in Canada by province covers the relevant laws and regulations.

Impact on Employment and Security Clearances

Inconclusive polygraph results can have significant implications in employment contexts, particularly for positions that require security clearances or involve law enforcement.

Federal Government and National Security

For federal positions requiring security clearances, polygraph examinations are often a mandatory part of the screening process. Agencies like the NSA, CIA, FBI, and other intelligence community organizations use both counterintelligence-scope and full-scope polygraph examinations. Our guide on national security polygraph testing provides comprehensive details.

When a national security polygraph produces an inconclusive result, the typical agency response includes:

• Scheduling a retest, usually after a waiting period of days to weeks
• Continuing the background investigation through other means
• Multiple inconclusive results may delay or potentially derail the clearance process
• An inconclusive result alone is generally not grounds for automatic disqualification

Law Enforcement Pre-Employment

Police departments and other law enforcement agencies routinely use pre-employment polygraph testing. Candidates who receive an inconclusive result on a pre-employment polygraph for police positions may face:

• A required retest within a specified period
• Temporary hold on their application until retesting is complete
• In some competitive hiring cycles, an inconclusive result may effectively eliminate a candidate if other applicants passed

Private Sector Employment

Private sector polygraph testing is heavily regulated by the Employee Polygraph Protection Act (EPPA), which prohibits most private employers from requiring polygraph tests. Exceptions exist for certain industries (security services, pharmaceutical manufacturers) and for specific-incident investigations. When an inconclusive result occurs in a permissible private-sector examination:

• The employer cannot take adverse action based solely on the inconclusive result
• EPPA protections apply regardless of the test outcome
• The investigation must continue through other means

What To Do After Receiving an Inconclusive Result

Receiving an inconclusive polygraph result can be frustrating and confusing. Here are the concrete steps you should consider taking:

How to Challenge an Inconclusive Polygraph Outcome

If you believe your inconclusive result was caused by examiner error, procedural problems, or other preventable factors, you have several avenues for challenging the outcome.

Review Test Records for Procedural Errors

Carefully examine all test documentation for evidence of procedural irregularities. Key items to check include:

• Was the pre-test interview conducted thoroughly?
• Were all questions reviewed with you before data collection began?
• Were a minimum of three charts collected?
• Were the sensors properly placed and functioning?
• Did the examiner follow a validated testing format?
• Was the scoring conducted according to established protocols?

If you discover issues with your examination, our resource on what to do if you received inaccurate polygraph results provides step-by-step guidance.

Seek Independent Quality Review

A qualified, independent polygraph examiner can review your test data and provide a professional assessment of whether the inconclusive determination was appropriate. This reviewer should be someone with no connection to the original examiner or requesting party. They can evaluate:

• Data quality across all physiological channels
• Accuracy of the original scoring
• Whether the test format was appropriate for the situation
• Whether comparison questions were properly constructed
• Whether artifacts or other data issues were properly handled

File a Formal Complaint

If you believe the examiner engaged in unprofessional or unethical conduct that contributed to the inconclusive result, you can file complaints with:

• The American Polygraph Association (APA) if the examiner is a member
• The state licensing board in jurisdictions that regulate polygraph examiners
• The examiner’s employer or contracting agency
• Our report fraudulent practices page if you suspect serious ethical violations

Preparing for a Polygraph Retest

If you decide to undergo a retest after an inconclusive result, thorough preparation can significantly improve the likelihood of obtaining a definitive outcome. Our comprehensive guide on how to prepare for your polygraph test covers general preparation, but here are specific considerations for retests:

Address Medical Factors

• Consult your physician — Discuss any medical conditions or medications that may have affected your previous test. Ask whether medication timing can be adjusted (never stop medications without medical supervision).
• Provide medical documentation — Share relevant medical information with the examiner before the retest so they can account for known conditions.
• Manage temporary conditions — If illness or fatigue contributed to the inconclusive result, schedule the retest for a time when you are feeling your best.

Reduce Anxiety

• Understand the process — Familiarize yourself with what you need to know before taking a lie detector test, what the examiner will ask, and what to expect during each phase. Knowledge reduces fear.
• Practice relaxation techniques — Deep breathing exercises, mindfulness meditation, and progressive muscle relaxation can help manage test-day anxiety.
• Get adequate sleep — Ensure you are well-rested before the examination. Fatigue exacerbates both anxiety and physiological irregularities.
• Arrive early — Give yourself plenty of time to settle in and acclimate to the testing environment.

Request a Different Examiner or Format

If you believe the original examiner’s approach contributed to the inconclusive result, it is reasonable to request a different examiner for the retest. You may also ask whether a different testing format would be more appropriate for your specific situation. Different polygraph techniques have different strengths and sensitivities.

Communicate Openly During the Pre-Test

During the retest pre-test interview, be completely transparent about:

• Your previous inconclusive result and any factors you believe contributed to it
• Any medical conditions, medications, or recent health changes
• Any concerns or confusion about the test questions
• Any significant life stressors that might affect your physiological state

This information helps the examiner optimize the testing procedure and account for known variables.

Emotional and Psychological Support

The psychological impact of an inconclusive polygraph result should not be underestimated. Depending on the context — whether it involves a criminal investigation, employment opportunity, relationship issue, or probation requirement — the emotional toll can be significant.

Common Emotional Responses

People who receive inconclusive results commonly experience:

• Frustration — The lack of a clear answer can feel like wasted time and effort, especially if you expected the test to vindicate you.
• Anxiety — Uncertainty about what comes next and how others will interpret the result.
• Anger — Particularly if you believe the inconclusive result was due to examiner error or poor testing conditions.
• Self-doubt — Even though an inconclusive result is not a failure, some people begin questioning themselves.
• Stigma concerns — Worry about how others (employers, family, legal professionals) will perceive the result.

Coping Strategies

• Seek professional support — A therapist or counselor can help you process the emotional impact, particularly if the polygraph is related to a traumatic situation.
• Educate yourself — Understanding the technical reasons behind inconclusive results (as covered in this article) can help reduce anxiety and self-doubt.
• Lean on trusted support networks — Share your concerns with trusted friends or family members who can provide perspective and encouragement.
• Focus on controllable factors — Rather than dwelling on the inconclusive result, direct your energy toward the steps you can take, such as preparing for a retest or consulting with experts.
• Maintain perspective — Remember that inconclusive results are relatively common and are a recognized, legitimate outcome of the testing process.

Understanding Polygraph Accuracy and Limitations

Inconclusive results exist, in part, because the polygraph is not a perfect instrument. Understanding the broader context of polygraph accuracy helps put inconclusive results in proper perspective.

The polygraph does not directly detect lies. Instead, it measures physiological responses that are correlated with, but not unique to, deception. The same physiological changes that accompany deception — increased heart rate, changes in breathing, elevated skin conductance — can also be produced by anxiety, fear, confusion, anger, and various medical conditions. Our article on 5 reasons why a polygraph test may not be accurate explores these limitations further.

This inherent limitation is precisely why the inconclusive category exists. Rather than forcing every examination into a binary truthful/deceptive determination — which would increase error rates — the inconclusive zone allows examiners to acknowledge when the data is genuinely ambiguous. In this sense, an inconclusive result represents the polygraph system working as designed: refusing to render an opinion when the evidence is insufficient.

The Role of Electrodermal Activity

The electrodermal activity (EDA) or galvanic skin response (GSR) channel is often the most discriminating component of the polygraph. When EDA data is compromised — due to excessively dry or calloused skin, excessive sweating, certain medications, or sensor placement issues — the overall examination is more likely to produce an inconclusive result. For a technical deep dive, see our article on electrodermal activity in polygraph testing.

Reducing Inconclusive Rates: What the Industry Is Doing

The polygraph profession continues to develop techniques and technologies aimed at reducing inconclusive rates while maintaining accuracy:

• Improved scoring algorithms — Computer-assisted scoring systems are increasingly sophisticated and can detect subtle patterns that human scorers might miss.
• Better test formats — Ongoing research into question formulation and test structure helps optimize the discriminative power of examinations.
• Enhanced quality control — Organizations like the APA continue to strengthen standards for examiner training, certification, and quality assurance.
• Supplementary technologies — Some practitioners are exploring complementary technologies alongside traditional polygraph instruments to improve overall accuracy.

Bottom Line: An Inconclusive Result Is Not the End

An inconclusive polygraph result can feel like a setback, but it is not a dead end. It is a recognized, legitimate outcome that reflects the honest complexity of measuring human physiological responses. The key points to remember are:

• Inconclusive does not equal deceptive. These are fundamentally different determinations.
• Multiple factors — medical, technical, procedural, environmental, and examiner-related — can contribute to inconclusive outcomes.
• You have rights and options, including obtaining your test records, seeking independent review, filing complaints when warranted, and requesting retests.
• Proper preparation, including addressing medical factors and managing anxiety, can improve outcomes on a retest.
• Working with an experienced, qualified, and professional polygraph examiner from the start is the single best way to reduce the risk of an inconclusive result.

If you have received an inconclusive polygraph result and need guidance on your next steps, contact our team for professional consultation. We can help connect you with qualified examiners, provide independent data review, and advise you on the best path forward based on your specific situation.