The polygraph operates by recording changes in a person's heart rate, breathing and perspiration during questioning. These changes are recorded by the computerised polygraph in a chart format, which can then be analysed by the examiner. The Polygraph charts are generated by attaching the following components to the subject.
Pneumograph
Two pneumograph tubes are placed around the subject's upper chest and abdomen on the outside of their clothing, these record changes in the subjects respiration.
G.S.R
The GSR or Galvanic Skin Response is recorded by placing two attachments across the fingers on one of the subject's hands. These trace changes in skin perspiration during the examination.
Cardiosphygmograph
This component traces changes to the subjects blood pressure and pulse rate and it is similar to the pressure cuff used by doctors when taking your blood pressure.
The Polygraph Test
A Polygraph test takes between 2 to 3 hours and consists of three phases; a pre-test interview, the actual polygraph examination, and analysis of the recorded response (charts).
Pre-test interview & formulation of questions
During the pre-test interview the examiner will explain how the polygraph works and discuss the issue in question with the subject. Together the examiner and subject will formulate and review all of the questions to be asked during the polygraph test. Only the questions formulated and reviewed in the pre-test interview will be asked during the examination, there are no surprise questions, the subject can rest assured that they are fully aware of the content of all of the questions and that they have had the opportunity to discuss them in detail with the examiner prior to the test commencing.
The Polygraph Examination
During this phase the subject will be attached to the polygraph. Only the questions which were formulated and reviewed during the pre-test interview will be asked (3 or 4 times) and the responses will be recorded by the computerised polygraph equipment.
Analysis of Charts
Once the examination is concluded the examiner will analyse the results before giving a decision as to the subjects truthfulness or deception to the given issue.
How reliable is Polygraph Testing?
The polygraph is highly reliable, providing the person using it is properly trained and the technique they use is validated. The American Polygraph Association (APA) has conducted studies which show the reliability of the tests to be as high as 98%. The critical issue here is that the examiner has graduated from an APA training school, that they are experienced, have undergone continual professional development and the results are quality controlled by a qualified instructor. Engaging the services of Polygraph International (UK) gives you that confidence and peace of mind.
