Another name for a lie detector is a polygraph. It is a machine capable of determining if someone is lying or telling the truth. The lie detector will monitor the physiological function of the person undergoing the test to know if the person is telling the truth or to. The test is usually carried out by an expert in psychophysiology and the expert is responsible for interrogating the individual undergoing the test. Polygraph can be used to screen prospective employees by the federal government for government positions. While the lie detector may be widely used by both government and private organizations, it is considered as not being reliable by many people as some people successfully beat the lie detector. Due to the doubt casted on the reliability of the lie detector, the evidence obtained from it is considered as not being acceptable in a court of law.
How does it work?
What the lie detector does is to measure various physiological functions and the functions measured depend on the particular type of lie detector used in that particular instance. There are several physiological function measured, but the most popular among them are sweat level, rate of respiration, heart rate and blood pressure.
When preparing the person for examination under the lie detector, the expert will first wear a blood pressure cuff around the arm of the subject to measure the blood pressure and the heat rate of the person under examination. You can visit https://www.liedetectortest.uk for more information about the subject matter.
Aside from the blood pressure cuff, two tubs are also passed around the chest of the subject and around the abdomen; the two tubes measure the subject’s rate of respiration. As the subject breathes, the air pressure in the tube will change. Also, electrodes are connected to the fingertips of the subject the electrodes work by measuring the sweat level of the subject. Rise in the sweat level brings about a freer flow of electrical current through the electrodes. The lie detector is responsible for recording all the physiological changes or responses in the course of the interrogation.
The examiner works by using various techniques in the course of the test and this ensures that the result obtained is accurate. Many experts are of the opinion that it is better that the examiner discuses with the subject before the test takes place so that a baseline can be established for the purpose of each function being measured.