Digital Media Concepts/Polygraph

The polygraph is a type of lie detector that determines the result by measuring one’s body response by testing pulse rates, blood pressure and breathing pattern. This instrument is used by many agencies to help detect truthfulness.

File:Polygraph Test
Test Procedure

Inventor edit

John Augustus Larson was the original inventor of the polygraph. He was a part-time police officer at UC Berkeley while he was earning his Ph.D. in physiology. When a person was undergoing questioning, the concept for the device was to note nervousness based on changes in blood pressure/pulse and respiratory rates. In the early 1920s, Larson created a method so that a permanent record could be created and evaluated on a rolling drum of paper while recording information on the changes in blood pressure/pulse and respiratory rates. [1]

Purpose edit

The most popular lie detection test that is used in the United States are polygraphs. They are used for screening applicants to dictate if the candidate’s application is honest and trustworthy. Employees who work in security-sensitive occupations and those with jobs that need to obtain a high level of clearance are often required to pass a polygraph examination. Polygraphs can also be used to help law enforcement by using the test results of suspects in a crime to guide them into figuring out who is being truthful. [2]

Reliability edit

Polygraph tests are valuable instruments that are useful in detecting truthfulness and deceitful behavior especially in crime investigation departments and sensitive national security occupations. Although they have a major significance to digital technology by detecting any deception and obtaining truth, there is a lot of controversy on how accurate and reliable the polygraph is. The American Polygraph Association estimates the polygraph’s accuracy to be about 87% which means that the polygraph results can be wrong 13% of the time. In 2003, a large team of scientists with the National Academy of Sciences was able to conclude that the polygraph was less accurate than previously claimed. Some scientists even claimed that the accuracy might be as low as 75%. [3]

History edit

1921: John Augustus Larson invented the first polygraph which was suitable to use in criminal investigation and was considered to be one of the greatest inventions of all time.

1925: Leonarde Keeler advanced Larson’s polygraph by developing metal bellows and a kymograph. The metal bellows helped create more accurate results when testing blood pressure, heart rate, and respiration patterns while the kymograph allowed the recording pens which allowed chart pens to be pulled under at a constant speed.

1936: Keeler added a physiological component that measured the changes in a person’s skin resistance called the Psychogalvanometer.

1947: John E. Reid developed the Reid Control Question Technique which was a surprise control question that was inserted in the relevant/irrelevant technique.

1948: Leonarde Keeler founded the Keeler Polygraph Institute which was the first polygraph school in the world.

1954: Three federal government agencies, the Operations Research Office (ORO), the CIA, and the National Security Agency, officially started to use the polygraph for general security screening.

1973: The Lafayette Instrument Company was the first in the world that embodied the wishes of all polygraph examiners and revolutionized the lie detection market by creating the first polygraph (PGS)

2007: The first wireless computerized polygraph in the world was invented by Lafayette Instrument Company (LX5000-SW)

2008: The ultramodern portable lie detector was created by the Lafayette Instrument Company for the Pentagon. [4]

Polygraph Testing Techniques edit

Polygraph tests use several different questioning techniques that measures things like blood pressure, a person's breathing, heart rate, and sweating on the palms. One of the most commonly used testing formats in criminal investigations is the Control Question Test (CQT). Although using the results against a suspect is often not allowed to incriminate them, it can help guide law enforcement to learn if there is a reason to doubt what they have to say. The Guilty Knowledge Test (GKT) is another way of taking the polygraph test that includes creating a multiple-choice test involving information that only a guilty suspect would know about. A bigger reaction would appear if someone who was guilty were to be taking the test with knowledge on the criminal investigation compared to someone who is innocent and didn’t understand the information in the test. [5]

References edit

  1. "John Augustus Larson," accessed October 12, 2021,
  2. "Lie Detection and the Polygraphy," accessed October 12, 2021,
  3. "Do Lie Detectors Really Work?," accessed October 12, 2021,
  4. "History of the Polygraph," accessed October 12, 2021,
  5. "The Truth About Lie Detectors (aka Polygraph Tests)," accessed October 12, 2021,