An inconclusive result on a lie detector test means the examiner couldn’t determine whether you were being truthful or deceptive. Your physiological responses fell into a gray zone, not strong enough to call deceptive, but not clear enough to call truthful either. It’s not a pass or a fail. It’s the polygraph equivalent of “we can’t tell.”
How Polygraph Scoring Works
A polygraph measures three things while you answer questions: your breathing rate, your sweat gland activity, and your cardiovascular response (blood pressure and heart rate). The examiner compares your reactions to relevant questions (“Did you steal the money?”) against your reactions to control questions designed to provoke a mild stress response in everyone.
Each comparison gets a numerical score. If your reactions to the relevant questions are much stronger than your reactions to control questions, you score in the negative range, which points toward deception. If your reactions to control questions are stronger, you score in the positive range, pointing toward truthfulness. These individual scores get added up into a grand total. A combined score of +6 or higher typically indicates no deception. A score of -6 or lower indicates deception. Anything between those two cutoffs lands in inconclusive territory. The exact thresholds can vary depending on the scoring method used, but the principle is the same: your responses weren’t clearly on either side of the line.
How Common Inconclusive Results Are
Inconclusive outcomes are far from rare. A review of polygraph research published by the Office of Technology Assessment found that inconclusive rates ranged from 0% to 53% depending on the study, the scoring method, and whether the person was actually being deceptive. In one well-known study by Barland and Raskin, 35% of examinations came back inconclusive. Other studies reported rates as low as 4% to 10%.
The scoring method makes a big difference. In pre-employment screening studies, one approach produced inconclusive results for 19% of truthful subjects, while a different scoring method applied to the same data dropped that to 8%. This wide variation is part of why polygraph results remain controversial: the same person’s test could be scored as inconclusive under one system and scored as truthful or deceptive under another.
What Causes an Inconclusive Result
Several factors can push your results into the inconclusive range, and many of them have nothing to do with honesty.
Anxiety and nervousness. A polygraph works by detecting stress responses. If you’re someone who runs anxious in general, or if taking the test itself makes you extremely nervous, your body may react strongly to every question, including the harmless ones. That makes it harder for the examiner to distinguish meaningful reactions from baseline anxiety. Clinical anxiety disorders are particularly likely to muddy the results.
Medications. Certain drugs directly affect the body systems a polygraph measures. Beta-blockers, commonly prescribed for high blood pressure and anxiety, blunt your physiological stress response. That dampening effect can flatten the differences between your reactions to different questions, increasing the chance of an inconclusive or false-negative result. Some antimalarial drugs can also interfere by affecting the autonomic nervous system while simultaneously causing anxiety and depression, pulling your responses in unpredictable directions.
Inconsistent responses across charts. A standard polygraph exam runs the same set of questions multiple times, typically three rounds. If your reactions to a particular question are strong in one round but weak in another, the scores may partially cancel each other out, landing you in the inconclusive zone. Research from Carnegie Mellon has pointed to this response variability within individuals as a persistent problem in polygraph data, noting that it’s often unclear whether shifting responses reflect habituation (getting used to the questions) or genuine differences in how the person processes each question.
Physical factors. Fatigue, sleep deprivation, illness, and even how much caffeine you had that morning can alter your heart rate and breathing patterns enough to affect results. These aren’t things most people think to control for before a polygraph appointment.
What Happens After an Inconclusive Result
The American Polygraph Association recognizes four possible outcomes for a deception test: Deception Indicated, No Deception Indicated, Inconclusive, and No Opinion. An inconclusive result is a standard, formally recognized outcome, not a technical error or a sign that something went wrong with the equipment.
In most cases, you’ll be offered or required to retake the test. The timing varies. For federal security clearance polygraphs, retests commonly happen weeks to a month or more after the first attempt. One account from a government contractor described being tested a second time about a month after the first inconclusive result, only to get another inconclusive on different questions during the retest.
The practical consequences depend heavily on context. For law enforcement or intelligence agency hiring, an inconclusive result usually delays the process rather than ending it. You typically get at least one more chance. For criminal investigations, polygraph results generally aren’t admissible in court regardless of the outcome, so an inconclusive result has limited legal impact.
Inconclusive Results and Security Clearances
If you’re going through a polygraph for a security clearance, an inconclusive result can feel alarming, but it carries important protections. Under Security Executive Agent Directive 4 (SEAD 4), no adverse action can be taken against your clearance solely on the basis of a polygraph result. That applies to inconclusive results, and it also applies to results scored as deception indicated. If the polygraph flags a possible concern, the agency needs confirmation from another source of information before it can affect your clearance status.
In practice, this means an inconclusive result won’t by itself cost you a security clearance you already hold. It may, however, delay or complicate the process of gaining access to a new program or position that requires a polygraph as a condition of entry. The agency will typically schedule a retest rather than making a final determination based on an inconclusive outcome.
Why Inconclusive Doesn’t Mean Suspicious
A common worry is that the examiner privately believes you’re lying but is calling it inconclusive as a softer label. That’s not how the scoring works. The numerical system is designed with the inconclusive range specifically because human physiology is noisy and variable. People react differently based on their baseline anxiety, their physical health, their familiarity with the testing process, and even their gender. Research has documented that these individual differences are large enough to make clear-cut scoring impossible for a meaningful percentage of test-takers.
The APA’s own standards also allow examiners to issue an inconclusive conclusion when there’s an “identified external factor that reduces confidence in a decision that would otherwise be based on the polygraph data.” In other words, if the examiner notices something during the test that could be skewing the results, like unusual breathing patterns or signs of a medical condition, they can appropriately call the result inconclusive rather than forcing it into a pass or fail category. That’s the system working as intended, not a red flag about your honesty.