How is a polygraph test performed?

A polygraph examination is carried out in order to obtain information regarding cases that have occurred. The test is carried out by means of a device that detects and records physiological events that are defined as such that it is possible to know whether these are false or true.

The physiological events in which the subjects are analyzed are respiratory events (faster breathing), the circulatory system (faster flow), the heart system (rapid pulse), and skin conductivity (hyperhidrosis).

How is the test performed?
Polygraph testIn order to detect these physiological changes, a number of devices are attached to the body:

Chest Breath Detector and Diaphragm Breathing Detector - When a person lies often, his breathing becomes faster (shorter breathing and breathing ). The detector allows the examiner to identify such situations and "mark" them as moments when the person may be lying.

Sleeve for measuring blood pressure and pulse - When a person lies his blood pressure rises and his pulse increases.

Electrical conductivity detectors of the skin - for identification of hyperhidrosis, characteristic of states of lying.

CARD FOR DETECTING MUSCLE MOVEMENT - When a person lies, this is sometimes characterized by an involuntary movement of muscles. The pillow allows the examiner to identify these movements and obtain more information about the speaker's reliability.

A device for measuring teeth in blood flow - It was found that when a person lies, there is more blood flow to the head area. This device detects the changes in the flow and provides an additional parameter to determine the correctness of the signal.
Not all polygraph institutes have all these devices, but in order to obtain reliable results, according to the American Polygraph Association, a reliable polygraph test is one that uses at least the devices for monitoring the heart, breathing and electrical conductivity of the skin.

Step the questions
After the subject is connected to all devices, the question stage arrives. The examiner asks the subject three kinds of questions:

Relevant questions - questions that have a direct connection to the subject of the subject. It is important to note that the participant receives the questions before he is connected to the devices, in order to enable him to prepare and reduce the natural stress threshold caused by such an assessment.

Embarrassing questions - questions that are not relevant to the subject of the investigation and which the respondent has no reason to lie about. These can be general questions, such as the name of the subject, how many people are in his family, whether he is male or female, etc.

Comparative questions - questions designed to make the patient uncomfortable, to understand how he or she responds in stressful situations. These questions are not directly related to the subject of the investigation, and allow the examiner to know better when the subject lied and when not.

Analysis of test results
According to the responses of the examiners, the examiner can reach conclusions regarding the subject's credibility regarding the subject of the investigation. This type of test has between 85% and 95% success rate, so its relative reliability is not in doubt. Although the result of the polygraph test can not serve as a single evidence in court to prove a certain claim, it can certainly serve as a supporting evidence and strengthen the judges in their decisions.