Lie detector tests, commonly called polygraph tests, are the closest available resource to a truth detector. These tests are conducted on specialised machines and are used in criminal cases as part of interrogation to determine the truth. These machines record physiological responses such as heart rate, blood pressure, and respiration to gather data, which the polygraph examiner interprets.
Private agencies can also conduct lie detection tests for investigations such as pre-employment screening, legal dispute resolution, family matters related to custody, and more. However, these machines have limitations, and the test results are not 100% accurate. The American Polygraph Association reports test accuracy between 85-95%, whereas other independent agencies report lower accuracy rates.
Several factors can influence the accuracy of a lie detector test. The examiner’s skill, experience, expertise, and the subject’s conditions and characteristics play essential roles in the outcome.
Below, we have listed key elements categorised by type that can impact the accuracy of polygraph test results.
Key Examiner Factors
- Experience and Skill of the Examiner
- The examiner’s experience and skill significantly impact test accuracy. Experienced polygraph examiners effectively use testing protocols to interpret physiological responses more accurately. They also understand how to conduct the test with a subject to achieve the best outcome.
- Training Methods and Scoring Approaches
- Examiners are trained in different ways and scoring techniques to conduct a polygraph test, and how effectively they apply these during the test impacts the end result. The numerical scoring method is a widely used technique for achieving near-perfect test results.
- Examiner Bias
- Examiner bias refers to any pre-existing assumptions that the examiner might bring into the lie detector test. For example, if an examiner has already decided that a subject is guilty, they might unintentionally influence the results through their behaviour or tone. An examiner needs to approach each test neutrally.
- Examiner’s Approach to Questioning
- The questioning style of an examiner during a lie-detector test can highly affect the subject’s physiological responses. The subject might feel anxious during the test depending on the examiner’s wording, tone, and pace of asking questions, which might lead to heightened physiological responses.
- Examiner’s Trustworthiness Perception
- For the most accurate responses, the subject must remain calm throughout the lie detector test, so building trust between the examiner and the subject is essential. The subject is likelier to feel at ease if they believe the examiner is trustworthy.
Key Subject Factors
- Psychological Traits and Behavioural Impact
- Certain behaviours, such as low socialisation or emotional instability, may directly affect the physiological responses, making it more challenging to detect lies accurately. Individuals may exhibit reduced stress responses or show heightened physiological reactions, which could be misinterpreted as signs of lying.
- Drug Use
- Certain drugs, such as tranquillisers and beta-blockers, can suppress stress responses, making it harder for the examiner to detect deception. These medications work by lowering the physical indicators on which the polygraph test relies, ultimately leading to inconclusive or inaccurate readings.
- Health Conditions on Responses
- Physical health conditions such as heart disease and anxiety disorders can directly affect important physiological factors like heart rate and blood pressure, impacting the polygraph test accuracy.
- Countermeasures
- The subject might strategise using countermeasures in physical form (biting the tongue, tensing muscles, etc. ) or mental form (isolating thoughts, mental distractions, etc. ) to manipulate physiological responses during the test, resulting in false readings and inconclusive results.
- Gender-Based Differences
- Some studies believe that males and females show different patterns of physiological responses, which may affect the validity of polygraph testing. These differences could be due to biological variations, but unfortunately, few data exist to validate this claim, making it highly inconclusive.
Additional Factors
- The Testing Environment
- The surrounding environment plays a key role in calming down the subject’s nerves and heart rate, which helps obtain stress-free responses. Specialised facilities are designed to provide a controlled environment that minimises external distractions, leading to more accurate test results.
- The Importance of Equipment Quality
- Since its inception, various technological evolutions have occurred in the equipment used for polygraph testing to achieve highly accurate results. High-quality equipment ensures that the physiological data are recorded accurately, resulting in precise and reliable outcomes.
- Modern, high-quality polygraph systems can be integrated with additional technologies such as eye-tracking, facial recognition, and voice stress analysis tools to enhance the precision of test results.
Conclusion
Like everything else, a lie detector test has pros and cons, which we discussed in this blog. While a lie detector test is not 100% accurate, it can give near-perfect results if specific pointers are taken care of, such as the examiner’s experience and skill and the quality of the equipment.
At Global Polygraph Solutions, we are leading lie detector test specialists in the UK. We have conducted interviews in some of the most complex investigations for over 35 years. For more information, visit our About Us section, which provides further details on our services.
We’re here to assist you in any way we can. Contact us on our Helpline in the United Kingdom: +44 (0) 7770 464472 or request a free consultation here.