Polygraph testing is a method of detecting criminals. It is a popular lie detecting method which is frequently used among UK’s private investigators and law enforcing agencies. Currently, there are several agencies in the UK that can offer you their services concerning the polygraph tests, but before hiring any agency, you must be well informed about the polygraph test itself.

In a polygraph test, several vitals, such as the pulse rate, skin sensitivity, and blood pressure is measured and recorded when the suspect is being asked a routine set of questions. After that, a private investigator or a concerned official can start a routine interview of the suspect. In most cases, if the suspect is guilty, then his vitals will fluctuate noticeably.

  • Generally, the test is conducted for 2-3 hours. There are 2 phases of the polygraph test. In the first phase, the suspect has to answer a set of questions. In the second phase, the operator will collect the data during the interrogation. And in the third phase, the experts will analyse this data to find out whether the suspect is a criminal or not. Polygraph testing is the most used method by the UK’s leading private investigating agencies these days. During the first phase, the operator will discuss the routine questions with the suspect. He will explain the whole idea of polygraph and also ask about any major health related issues. The whole phase will take 60-90 minutes to complete. The operator will consult the private investigator about the general investigation and interrogate the suspect during this phase. The questions will be simple and they can mostly be answered by “yes” or no”.
  • In the second phase, the suspect’s vital statistics will be measured by the polygraph. The first set of routine questions will be repeated 4-5 times in this phase.
  • The third phase is mainly to analyse the data recorded in the second phase. The suspect’s truthfulness will be decided in this phase.


Polygraph Testing Method

The polygraph testing method follows a simple theory. Oftentimes, if a suspect is stressed for some reason (aka guilty conscience), then it will show on his/her physiological state (pulse rate, skin sensitivity, and blood pressure). In a polygraph test, these measurements are recorded impeccably, so any change in them during a particular question raises some red flags. Scientists have been researching about the changes in brain activity and polygraph testing for many years. They have undergone numerous hours to interpret them to catch the guilty persons. Generally, the suspect is attached to several things during the interrogation in a polygraph test.

Pnuemograph, Cardiosphygmograph, and Galvanic Skin Response (G.S.R) are some components that are used during a polygraph test. Pneumographs are attached to the chest of the suspect to record the breathing of the suspect. Cardiosphygmograph records the vitals (pulse rate and blood pressure) and Galvanic Skin Response (G.S.R) is used to track the skin sensitivity of the suspect during an interrogation. During a polygraph set, all questions must be asked 2-3 times to record the vitals of the suspect. If the person is guilty, they will surely fluctuate.