At Lie Detector UK, we frequently receive inquiries from individuals who believe they have failed a lie detector test despite telling the truth. This occurrence, known as a false positive, can be distressing, but it is important to understand how polygraph examinations work and why such results can happen.
How Does a Polygraph Work?
A polygraph measures physiological responses controlled by the Sympathetic Nervous System (SNS). These responses fluctuate based on factors such as perception, environment, and the significance of the questions being asked. The polygraph process evaluates these variations to determine whether an individual is being truthful.
It is crucial to note that general nervousness or anxiety does not impact the test results, as these emotions persist throughout the examination rather than being linked to specific questions. The polygraph focuses on changes in physiological responses rather than a person’s overall state.
13 Reasons Someone Might Fail a Polygraph
1. The Examinee Was Not Truthful About the Key Issue
If an individual is being deceptive about the subject matter of the test, a “deceptive” result is expected. Some people may continue denying allegations despite the outcome, believing the result to be incorrect.
2. Withholding Crucial Information
Even if an individual is mostly truthful, intentionally omitting relevant details can influence test results. Some examinees withhold information out of embarrassment or fear of repercussions, leading to an inaccurate outcome.
3. Uncertainty About Answers
Memory lapses due to alcohol, drug use, medication, or sleep deprivation at the time of the event in question can create uncertainty in responses. Since polygraph tests require definitive answers, any hesitancy can trigger a false positive.
4. Misunderstanding the Questions
If an individual struggles with comprehension due to language barriers or cognitive limitations, they may fail to fully grasp the examiner’s questions. This can lead to misleading results.
5. Misunderstanding the Polygraph Process
Polygraph testing is a psychological procedure, not a medical one. If an examinee does not fully understand the process or its purpose, their response patterns may be affected, leading to an inaccurate result.
6. Medication-Induced Impairment
Some medications can dull cognitive clarity, making it difficult for an examinee to fully comprehend the importance of specific questions. This lack of awareness may contribute to a false positive outcome.
7. Attempting to Manipulate the Test
Examinees who use countermeasures—such as altering breathing patterns, pressing toes against the floor, or contracting muscles—may unknowingly create irregular physiological markers. Even if the person is truthful, these unnatural responses can lead to a deceptive result.
8. Poorly Designed Questions
For a polygraph to be effective, the examiner must structure the questions correctly. Poorly framed or ambiguous questions can skew results, increasing the likelihood of a false positive.
9. Use of Unvalidated Testing Methods
A polygraph must adhere to scientifically validated testing formats. Some methods—such as the AMGQT or the R/I technique—lack proper validation, reducing test accuracy and increasing the risk of incorrect outcomes.
10. Failure to Follow Examiner’s Instructions
Examinees are required to remain still, avoid excessive movement, and answer questions clearly. Even minor physical movements, such as nodding or adjusting posture, can distort physiological data, affecting the final result.
11. Polygraph’s Natural Margin of Error
Even under optimal conditions, polygraph tests are not 100% infallible. A single-issue polygraph test has an accuracy rate of 93-95%, meaning 5-7% of truthful individuals may still fail. While polygraphs remain a highly effective tool, they are not perfect.
12. Excessive Number of Relevant Questions
Polygraph accuracy declines when too many relevant questions are asked. The most reliable polygraph tests focus on a single issue, while multiple-issue tests (with up to four questions) have reduced accuracy. Exceeding the recommended limit makes the results less reliable, with accuracy rates dropping to 50%—the equivalent of flipping a coin.
13. Insufficient Test Duration
The American Polygraph Association (APA) mandates that an exam should last at least 90 minutes to allow for proper pre-test discussions, question clarification, and examinee acclimation. Tests that are rushed or cut short may not yield reliable results.
Considering a Retest?
If you believe you have received a false positive result, it is advisable to identify potential reasons before undergoing a retest. Ensure that the next examiner is highly qualified and made aware of the circumstances surrounding the previous test.
At Lie Detector UK, we adhere to the highest professional standards to ensure that all polygraph tests are conducted with scientific accuracy and ethical integrity. If you require a lie detector test in the UK, contact us for a reliable and professional examination.
