Polygraph testing is based on the assumption that fluctuations in breathing, pulse rate, blood pressure, and perspiration are indicative of deception. In a nutshell, a polygraph compares a subject’s physiological responses to a question where the individual is supposedly tricked into lying (a “control question”) with his/her response to a question concerning the matter being investigated. If reactions to the “control” question are greater, the subject is deemed truthful. If reactions to the question on which the polygraph is attempting to determine truth or deception are greater, the subject “fails.” If reactions to both are approximately the same in size, the “test” is termed inconclusive.

How Accurate Is It?

The accuracy of the lie detector test is often brought under question. This is simply because of the nature of the test and the repercussions it holds for the test subject. Since the test measures physiological responses mentioned above, it is not 100 % accurate. This is due to the many variations occurring in physiological responses without a person lying. Simple stress and discomfort can raise the physiological responses being measured and register a false positive. Generally, if the surroundings are comfortable and the person administering the test is well – experienced, a polygraph test can be up to 90% accurate.

Court Admissibility

In the United Kingdom, polygraph test results are inadmissible in a court of law. This is owing to their nature. Since they measure physiological parameters alone, there are chances of false positives. In order to avoid construing a false positive as an admission of guilt, these are not considered reliable enough to be admitted in a court of law. However, any interviews conducted by a law investigation agency while the interviewee was hooked to a polygraph are admissible. It is essential to substantiate polygraph results with some other evidence to present it in court.


Polygraph tests can find application in a wide variety of areas. We often administer tests for companies looking to hire new employees, companies that suspect employees of not working or committing some fraud that is damaging to the company. For personal investigations, we often conduct polygraph tests on spouses to help them identify each other’s faithfulness. We also help parents who worry about their children keeping bad company or other firms where any sort of official interrogation is required. In all cases, we make it a point to obtain the requisite formal approval of the person being tested in writing.

Why Choose Us?

At Private Investigators UK, we have a team of certified, dedicated and well – qualified private investigators. A large number of them are from a law enforcement background, giving them some great additional interrogation skills. They have all undergone intensive training for conducting polygraph tests and are more than capable of cracking the toughest cases. Our detectives have often cracked cases that seemed impossible, simply due to their wealth of experience. Our services are highly customizable and we believe in delivering the utmost satisfaction to our customers. Feel free to get in touch with us for any further clarifications and to request a free quote.