Polygraph Test: What Is It and How Does it Work?

Various cultures have used different ways to detect deception at different times and ages in human history. Ascertaining individual honesty is of great significance, especially in such vital fields as national security, judiciary and criminal investigation, security screening, recruitment, and employee theft.

For instance, if investigating teams fail to establish the truth in criminal investigations, several criminals escape from punishment. But, at the same time, it may force many innocent crime suspects to receive penalties if the evidence is not in their favor. Greenville polygraph testing can provide a solution to this dilemma.

What Is a Polygraph?

A policeman and physiologist, John Larson, created the first polygraph in 1921 when he created an instrument that measured changes in the heart rate, respiration rate, and blood pressure. However, his work was influenced by William Marston and Vittorio Benussi.

Later in 1923, Marston attempted to have the polygraph test results used as evidence in United States v. Frye, but was rejected. However, Larson’s protege, Leonarde Keeler, continued working on the polygraph, and in 1935, it was used to convict two suspects in Portage, Wisconsin.

So, what is a polygraph?

First of all, what is a polygraph, and how does it work? A polygraph is also known as a “lie detector.” It is an instrument that measures physiological changes in blood pressure, heartbeat, respiration, and perspiration — reactions allegedly linked with the anxiety caused by lying — while a subject is asked questions.

A lie detector uses a device or procedure that measures several physiological indicators such as blood pressure, pulse, respiration, and skin conductivity. At the same time, a person is asked a series of questions. It is a reliable procedure because it works with the physiological condition of the human system.

The device is event-specific; it is used when deception is perceived in an individual. The polygraph records the individual’s physiological response to appropriately structured questions.

The examiner now reviews the person’s physiological response to the questions to decide whether the person is telling the truth. Polygraph tests are crucial in crime investigation, employee screening, or pre-employment screening.

How Does It Work?

The polygraph is an instrument with sensors attached to the individual taking the test. These sensors range from four to six, depending on the type of machine. The sensors record a person’s breathing rate, pulse (heart rate), blood pressure, and perspiration. The measurement of these areas is called physiological responses.

Breathing rate is typically measured by a pneumograph, a coil wrapped around a person’s chest that measures the frequency and intensity of a person’s respiration. Heart rate and blood pressure are calculated by using a blood pressure cuff.

Electrodes are connected to a person’s fingers to measure perspiration or electrodermal response. These electrodes can be disposable or small metal plates.

Initially, the data collected during a polygraph test was recorded using analog instruments. Then, the data would print out on a moving sheet of paper with several pens moving to report the data.

Due to this process, the record of an individual’s responses during the actual polygraph test is called a polygraph chart. However, most polygraph tests today use computerized recording systems to collect the data.

A polygraph examination has different phases. The first is a pretest phase, where the paperwork to administer the test gets completed. The examiner also explains the polygraph test process and answers any questions the individual taking the test may have.

The questions used for the actual exam are also reviewed during this phase to ensure understanding. When the polygraph test starts, the questioner asks three or four simple questions to establish the norms for the person’s signals.

The next is referred to as the chart collection phase. The examiner administers questions and collects several polygraph charts during this stage. The number of questions asked and the charts collected varies by case.

The final stage is the data analysis phase. During this stage, the information collected through questioning is reviewed and analyzed. The examiner, at this point, decides whether or not deception was present. At this time, the examiner will give the individual being tested an opportunity to explain their responses to some of the questions when needed.

The primary purpose of the polygraph test is to identify individuals that pose a threat to the country. It makes it reasonable to reduce cases of false security cases. Polygraph tests are also sometimes used by individuals seeking to convince others of their innocence and, in a narrow range of circumstances.

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Who Can Use a Polygraph?

People confess before, during, and (most frequently) after polygraph tests, so their use in police investigations is pretty common. Defense attorneys may choose to have their clients undergo polygraph testing to convince prosecutors to drop weak charges. However, no defendant or witness can be forced to take a polygraph test.

Federal government agencies such as the Department of Defense, Department of Justice, National Security Agency, the CIA, and state and local police departments often require the services of a lie detection company to screen potential applicants, suspects, or citizens.

Some companies equally subject their workers to a polygraph test. Truth is in demand, especially in the corporate world. To deal with cases of fake CVs, businesses are turning to their new best friend — the polygraph machine. Many firms are now approaching private forensic laboratories to conduct polygraph (lie-detection) tests on employees.

Polygraph tests are kind of magical instruments that help detect whether or not a person is lying. The underlying assumption behind polygraph testing is that telling lies is reflected in physiological or neurological responses. The human body tends to react differently when deliberately trying to hide the truth or facts.

The polygraph tests appear to be a better lie detection method than conventional interrogation. Generally, in traditional forms of interrogation, the crime suspects are subjected to long periods of repeated questions. In addition, the officers often use punitive measures to ascertain honesty and truthfulness.

The outcomes of such investigations may not be accurate as well. The painless and straightforward way of assessing honesty and truthfulness using polygraph tests might be more appropriate in this context.

It is essential to recognize that the results of a polygraph will not always be accurate. Some experts put the accuracy of the polygraph between 75% and 87%, as only subjects who can stay calm may pass the test. Some people even work with a trained examiner to learn how to beat the polygraph.

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