Human motives are complex and capricious.
Emotions, stress responses, and our capacity for conscious control are not always perfect. That’s why they are used in fields such as law enforcement, private investigations, and security screenings, often through the use of polygraph test.
Polygraphs, though popular, are not without limitations. They record physical readings — indicators such as heart rate, change in blood pressure, and skin conductivity — rather than truth or intent. As a result, findings can sometimes be inconclusive or even indicate deception where none exists.
This is not necessarily a checkmate on polygraph testing. Instead, it is understanding how such inconclusive or false results occur — and what to do next — that is the key.
Polygraph experts note that, while interpretation, verification, and retesting are critical components of handling such test results, whether these are done appropriately is crucial.
Here, we break down what inconclusive or false polygraph results mean, why they occur, and how to effectively deal with them.
Inconclusive And False Polygraph Results Explained
A polygraph test result is usually presented using one of the mentioned terms:
1. No Deception Indicated (NDI)
This indicates that the subject was telling the truth regarding the specific matter in question. Physiological responses are in line with confirmed truthful situations.
2. Deception Indicated (DI)
This result occurs when the participant’s reactions are similar to what researchers have measured in known cases of deception. In this case, the examinee is not ruled out as a suspect.
3. No Significant Reactions (NSR)
If none of the questions provoke strong physical reactions, the subject’s statements are taken as true.
4. Significant Reactions (SR)
Here, even relevant questions with a marked physiological reaction could imply deception. This finding suggests the examinee is withholding information regarding one or more topics tested.
5. Inconclusive (INC)
This is regarded as non-conclusive and can be caused by a lack of response or mixed results. Misleading or false results of a similar nature often have similar origins.
The odds of getting the result are relatively meager, according to several sources. But when such a result is reflected, these results don’t necessarily mean dishonesty is at play.
6. No Opinion (NO)
If the data is too distorted to interpret, a “No Opinion” is declared. This distortion can be intentional and caused by purposeful movements, such as coughing, sneezing, or nervous body language.
7. No opinion on Countermeasures (CM)
Countermeasures are possibly intentional strategies that examinees employ in order to influence their assessment. These can be anything from rhythmic breathing, cognitive distraction, or voluntarily experienced physical pain.
Examiners are instructed to observe these efforts. If detected, the outcome is marked as No Opinion by suspected Countermeasures.
Why Test Results Can Be Inconclusive: Physiological and Procedural Factors
One of the primary reasons for the conflicting data is in human stress reactions. The sympathetic nervous system activates under stress, causing spikes in heart rate and sweat production — whether you’re lying or, say, just anxious.
For example:
- Job applicants may display increased stress responses during a security clearance test, even when they’re being sincere.
- Someone anxious might produce irregular physiological readings that have nothing to do with lying.
Procedural issues are also responsible for such results, such as:
- Poorly phrased or confusing questions
- Incorrect sensor placement
- Environmental interferences, such as noise or changes in temperature
Experienced examiners in the field mitigate these issues by conducting pretest interviews, taking baseline measures, and standardizing question style to minimize potential misinterpretation. Take note that all these sessions are conducted on the same day.
False Positives Correction: Confirmatory Testing of Results by Retesting
Testing again is the best possible next step when polygraph test results signal deception, but all the evidence seems to indicate that it is not true.
Best practice is to have a formal verification process:
- Reviewing all data: computer chart scores and examiner observations
- Re-taking the test after a rest period to avoid the transfer of stress
- Employing different testing methods, such as the DL test or the R/I questions format.
One such example commonly referred to in professional circles is the applicant for law enforcement who “failed” an initial polygraph because they misunderstood a question. The results indicated no deception after clarification and a second interview, which demonstrates the importance of examiner feedback and reanalysis.
It’s critical to remember that a single polygraph reading, especially if it’s contested or questionable, should never be in and of itself a final result.
Why Does Examiner Experience Matter?
Not all polygraphs are created equal. The reliability of outcomes is highly dependent on the examiner’s competency and their adherence to scientific rigor.
The key components differentiating trustworthy testing from non-trustworthy testing are:
- Accreditation with a recognized professional organization, such as the APA or BPA.
- Application of universal scoring techniques, such as the Empirical Scoring System or the Objective Scoring System
By working with experienced professionals, you can be confident that practices such as chart reading, question development, and retesting are conducted in a manner supported by research and experience.
Final Thought
Although lie detector tests provide helpful information, they are not proof positive of truth or falsehood. Inconclusive or even false results underscore this truth, but they do not negate the value of the tool when used correctly.
It is wiser to consider polygraph results as just one piece of the investigative puzzle. Decisions regarding the final analysis of a subject are based on factors such as the investigator’s experience, the test environment, and the list of questions.
For enterprises, law enforcement agencies, or private users, adopting this or any other approach, knowing the bounds and benefits of polygraph testing helps make better decisions.
