Inconclusive Lie Detector Results: What Do They Mean?

Inconclusive Lie Detector Results: What You need To Know

Inconclusive lie detector results mean a polygraph examination did not produce sufficiently clear data for the examiner to classify the outcome confidently. An inconclusive result is not the same as failing a lie detector test. It does not establish that the person was lying, but it should not be treated as proof that they were telling the truth either. It means the available physiological data did not support a clear conclusion. Several factors can contribute to inconclusive results, including inconsistent physiological responses, anxiety, fatigue, health factors, question wording, movement and testing conditions.

What Does Inconclusive Lie Detector Results Mean?

During a lie detector test, sensors record physiological responses while a person answers structured questions. Depending on the equipment and testing technique, this physiological data can include changes in breathing, cardiovascular activity, blood pressure and skin conductivity. A blood pressure cuff and other sensors may form part of the polygraph equipment. The polygraph examiner analyses these responses using the appropriate testing and scoring method. If the data does not provide a sufficiently clear pattern, the outcome may be reported as inconclusive rather than truthful or deceptive. This means an inconclusive polygraph is neither a clear pass nor a clear fail. A deceptive result indicates that the response pattern met the criteria for deception under the technique being used. An inconclusive result means the examiner could not make a sufficiently clear classification from the available data. Understanding how lie detector results are interpreted can help distinguish between these outcomes.

Why Does a Polygraph Come Back Inconclusive?

There is no single reason for inconclusive polygraph results. Possible factors include:

• unusually high anxiety or emotional distress
• fatigue or lack of sleep
• illness, pain or physical discomfort
• relevant medical conditions or medication
• excessive movement during data collection
• difficulty remaining focused
• unclear or poorly constructed questions
• inconsistent physiological reactions
• distracting or unsuitable testing conditions
• insufficient data quality for reliable scoring

None of these factors automatically causes an inconclusive result. For example, someone experiencing extreme nervousness may show strong physiological reactions throughout the examination. Another person may produce responses that vary too much for the examiner to identify a sufficiently clear pattern. Because polygraph tests measure physiological responses rather than detecting deception directly, reactions caused by fear, confusion or discomfort can also be relevant. A trained examiner should therefore consider the complete examination rather than treating one change in heart rate, breathing or blood pressure as evidence that someone is lying.

Can Anxiety, Medication or Lack of Sleep Affect the Result?

Anxiety can affect physiological responses, but nervousness does not automatically cause an inconclusive lie detector result. Most people are likely to experience some degree of anxiety during a lie detector test, particularly when the examination concerns a relationship dispute, theft allegation, false accusation or another sensitive issue. The relevant question is whether severe anxiety or another factor interferes sufficiently with data collection or interpretation. Health conditions, medication, illness, pain and fatigue can also be relevant because they may affect a person’s physical condition or physiological reactions. Lack of sleep can affect a lie detector test, particularly through its effects on concentration, fatigue and stress tolerance. Medication and health conditions are also among the factors that can affect a polygraph test. Relevant circumstances should be disclosed to the examiner beforehand. Do not stop prescribed medication unless advised to do so by an appropriate medical professional. Alcohol, non-prescribed drugs or other substances should also be disclosed where relevant, as they may affect a person’s condition during testing.

How Do Questions and Testing Conditions Affect the Result?

Question formulation is an important part of a professional polygraph examination. Relevant questions should be clear, specific and understood by the person being tested before data collection begins. A vague or ambiguous question can create uncertainty about what is actually being asked. The person may react because they are confused or unsure how to answer rather than because they are being deceptive. During the pre-test interview, the examiner should therefore review the relevant questions and make sure the person understands them. There should not be surprise relevant questions during the recorded examination. The testing environment also matters. Unnecessary distractions, discomfort or other unsuitable conditions can interfere with concentration or data quality. Clear questions and a controlled environment cannot guarantee a conclusive result, but they help reduce avoidable problems during the examination.

How Does the Polygraph Examiner Affect the Result?

Examiner competence is an important part of the polygraph testing process. A professional examiner needs to understand question formulation, testing protocols, data collection, the testing technique being used and the interpretation of physiological responses. The American Polygraph Association publishes standards relating to examiner education, training, validated techniques and professional polygraph practice. Surfer also identifies examiner competence, experience and professional standards as important factors affecting the examination process. A competent examiner should also recognise when the available physiological data does not justify a definitive conclusion. Reporting an examination as inconclusive when the evidence is insufficient can be more responsible than forcing the test results into a truthful or deceptive classification.

Inconclusive vs False Positive and False Negative Results

An inconclusive result is different from a false positive or false negative. A false positive occurs when a truthful person is incorrectly classified as deceptive. A false negative occurs when a deceptive person is incorrectly classified as truthful. With an inconclusive polygraph, a sufficiently clear classification has not been reached in the first place. No lie detector test is 100% accurate, and inconclusive results are possible. Validated polygraph techniques can achieve accuracy rates above 90% when conducted properly by a qualified examiner, although test accuracy varies according to the technique, examiner, questions and testing conditions. Polygraph results should therefore be considered within the context of the complete examination rather than treated as standalone proof.

What Happens After an Inconclusive Polygraph Result?

If your lie detector test is judged inconclusive, the first step is to understand why the examiner could not reach a clear conclusion. Useful questions include:

• Was the entire examination inconclusive or only a particular issue?
• Was the physiological data inconsistent?
• Were the questions clearly understood?
• Did movement affect data quality?
• Were there problems with the testing environment?
• Could anxiety, fatigue, health or medication have contributed?
• Does the examiner consider another examination appropriate?

An inconclusive result may leave the original issue unresolved, but it should not be converted into evidence that someone lied simply because the test did not provide the expected outcome.

Can You Retake a Polygraph After an Inconclusive Result?

Yes, a retest may be appropriate in some circumstances. However, simply repeating the same lie detector test under the same conditions does not guarantee a different outcome. The examiner should first consider why the original examination was inconclusive. If unclear questions, fatigue, illness, poor testing conditions or another identifiable factor affected the test, that issue should be addressed where possible before another examination. A second test may produce clearer data, but no professional examiner should guarantee a pass or a conclusive result.

Can an Innocent Person Receive an Inconclusive Result?

Yes. Innocent people can receive inconclusive results. A truthful person may be anxious, tired, unwell or emotionally affected by the issue being examined. Their physiological responses may also fail to produce sufficiently clear data for classification for other reasons. An inconclusive outcome therefore does not establish deception. This is related to, but different from, whether innocent people can fail lie detector tests. A false positive involves an incorrect deceptive classification. An inconclusive result means no sufficiently clear classification was reached.

FAQs

Can You Pass a Polygraph With Inconclusive Results?

An inconclusive result is neither a clear pass nor a clear fail. A later examination may produce a conclusive result, but that does not change the original test from inconclusive to passed.

What Happens When a Polygraph Test Is Judged Inconclusive?

The examiner should explain that the available data did not support a sufficiently clear classification. The circumstances of the examination can then be reviewed to determine whether any identifiable factor contributed and whether a retest is appropriate.

Why Does a Polygraph Come Back Inconclusive?

Possible reasons include inconsistent physiological responses, severe anxiety, fatigue, health factors, medication, movement, unclear questions, unsuitable testing conditions or insufficient data quality. No single factor automatically causes an inconclusive result.

How Common Is It to Fail a Polygraph?

There is no single failure rate that applies to every polygraph test. Outcomes depend on factors including the testing technique, questions, examiner and individual circumstances. A failed or deceptive result is also different from an inconclusive result.

Can Anxiety Make a Polygraph Inconclusive?

Severe anxiety can affect physiological reactions and may make the data more difficult to interpret, but nervousness does not automatically produce an inconclusive result.

Is an Inconclusive Result a False Positive?

No. A false positive incorrectly classifies a truthful person as deceptive. An inconclusive result means a sufficiently clear truthful or deceptive classification could not be reached.

Conclusion

Inconclusive lie detector results are neither an automatic pass nor an automatic fail. They mean the polygraph examination did not produce sufficiently clear physiological data for a confident classification. Anxiety, health factors, fatigue, question wording, movement, testing conditions and data quality can all be relevant, although none automatically causes an inconclusive result. A professional polygraph examination therefore depends on clear questions, appropriate testing conditions, validated techniques and a trained examiner who is prepared to report an inconclusive outcome when the data does not support a definitive conclusion. If you receive an inconclusive result, the appropriate next step is to review the examination with the examiner, understand why the result was unclear and determine whether any identifiable issue should be addressed before considering another test.