The modern polygraph is a product of nearly 150 years of invention and innovation. Today’s modern devices are nothing like the first machines put into service in the 1910s and 1920s. They operate on computerized systems, yielding remarkably accurate results.

Along the timeline of polygraph development, we find several individuals developing prototypes that would lead to further advancements in polygraph science and technology. So, what are the types of lie detector machines? What’s the history of these devices, and where are they now?


A Brief PSA In the History of Polygraph Devices

Polygraph science started in the late 1800s with discoveries in how the body reacts to stressful scenarios. Some say the first use of polygraphy began in Ancient China, where interrogators would stuff suspects’ mouths with dry rice. If the rice came out wet, they were telling the truth; if it was dry, they were lying.

However, this hit-and-miss methodology would develop into hard science in the late 1800s. The following men all made significant contributions to polygraphy.

  • Sir Francis Galton (1879)
  • Cesare Lombrosso (1895)
  • Angelo Mosso (1895)
  • Albert Stiker (1897)
  • Max Wertheimer (1904)
  • S. Veragut (1907)
  • Dr. Hugo Mustenberg (1908)
  • Vittorio Benussi (1914)


What are the Different Types of Lie Detector Machines?

While plenty of men contributed to the early formation of polygraph science, four standouts were above the rest. These individuals were the first to invent polygraph machines monitoring the vital signs initiated by the body’s “fight-or-flight” response.

Each of these individuals played a significant role in the other’s design and development of their unique lie detector machine. Some were purpose-built for deception detection, while others were not. Let’s unpack each contribution made by the inventors and innovators of polygraph science.


Dr. James McKenzie – The Polygraph

The first man to develop a polygraph device was Dr. James MacKenzie. As a trained cardiologist, MacKenzie didn’t build his instrument for the purpose of deception detection. Instead, he designed it to provide insight into his patient’s pulse rate and AV activity.

Ironically, MacKenzie coined the term “polygraph,” using it as the moniker for his device, despite never being involved in deception detection. The doctor would himself die of cardiovascular disease in 1928, suffering from angina and latent results from cardiac infarction.


William Marston – The Systolic Blood Pressure Test

William Marston, otherwise remembered as the creator of the “Wonder Woman” comic character, was also a trained lawyer and psychologist. Marston developed the “Systolic Blood Pressure Test” after his wife gave him the idea, mentioning she felt her blood pressure rise whenever she got mad.

Marston created a basic polygraph device monitoring changes in suspects’ blood pressure under criminal interrogation. Despite his efforts, he couldn’t get the courts to approve his device results as admissible evidence. As a result, the courts ended up creating the “Frye” rule, mostly outlawing the use of polygraph results in criminal trials.

However, Marston inspired “the Father of the Polygraph,” John A. Larson.


John Larson – The Sphyggy

John Larson and Leonard Keeler were the two men creating the biggest impact on polygraph science. Larson studied at UCLA, moonlighting with e Berkeley Police Force. His interests in psychology, law and police work led him to William Marston’s work on his Systolic Blood Pressure Test.

Larson tested his device on his fellow students, asking them to pick a card from the deck before returning it. He would ask them to deny picking the card as he showed them each one in the deck. According to sources, he sometimes rigged the deck to get the desired result.

However, his prototype device was a smashing success with the law enforcement community. Larson’s “Sphyggy” helped convict hundreds of criminals before Leonard Keeler redesigned his invention with several innovations.


Leonard Keeler – The Keeler Polygraph

Keeler was the biggest influence on modern polygraph science. A friend of Larson’s and his partner in science at the Berkeley Police Department, Keeler took Larson’s design and improved it. He did away with the need for smoke paper, replacing it with chart paper and ink pens. As a result, his innovation was far easier to set up and offered easier storage of the data recorded during the test.

Keeler also introduced the ability to track skin electrical responses in his device, improving the accuracy of the polygraph. Keeler lost his original “Emotograph” in a fire at his apartment but had it redeveloped by Associated Research in Chicago.

Todays, Keeler’s contributions to polygraphy are considered the most revered in the industry. Some state that without Keeler, there would be no modern polygraph, securing him the moniker of the “Father of the Modern Polygraph.”


Associated Research – Redeveloping the Keeler Polygraph

Shortly after its debut, Leonard Keeler lost his “Emotograph” polygraph in a fire at his apartment in 1925. After the event, Keeler approached “Associated Research,” a Chicago-based firm, to assist with redeveloping the Emotograph.

Associated Research proved to be a reliable partner, redeveloping the device for use in the field. However, Keeler chose them as his preferred company for advancing his design in the coming years before his death in 1949.

Associated Research worked closely with Keeler to redesign the Keeler polygraph on several occasions. The result was a string of polygraph models released until the late 1960s. Each model was an advancement of the previous one, introducing new features aiding its utility and operation in the field.

Here is a quick breakdown of the devices produced by Associated Research before and after Keeler’s passing.


The Keeler #302

The Keeler model #302 was the successor to the Emotograph in the 1950s. This innovation introduced a “third channel,” known as a “psychogalvanometer.” The purpose of this addition was to measure electrical activity in the skin under questioning, enhancing the device’s accuracy,


Keeler Model #302C

The Keeler Model #302 underwent two modifications after its initial release. Its successors were Model 302B and Model 302C. Both models featured a steel housing with chromium trim and a wrinkle finish.


Keeler Model #304

This model was released in 1952. The design innovations included a cardiosphygmograph, pneumograph, and two pen units, further improving the accuracy of Keeler polygraphs. Model #304 featured an Esterline Angus two-speed sprocket drive kymograph. It was a huge technological leap, but only 20 units were manufactured by Associated Research, making it one of the most sought-after collector items for polygraph historians.


Keeler Model #6303

This model was a hybrid between the Keeler model #302 and model #6308. It included the best of both instruments in the series, providing excellent results in the field.


Keeler Model #6308

This model was the first in the legendary “Pacesetter” series. It was specifically designed for the military and for use in interrogations. The #6308 was the first Keeler polygraph to include the use of transistors in its design. The model was so successful that it was adopted by police services across the country. As one of the most popular Keeler models, the #6308 was in service until the late 1960s and, in some states, until the 1970s.


Keeler Model #6318

This tri-channel polygraph instrument was identical to #6308 in its design. However, it was capable of operating on battery power. The #6318 featured an individual inking system coupled with a sprocket drive kymograph.


Keeler Model #6317

As possibly the most infamous Keeler polygraph, model #6317 featured completely transistorized circuitry. It was the first portable instrument utilized by the CIA in the Korean War. The device was so popular with the government agency that it continued service into the 1960s. The CIA would use it to interrogate Cuban nationals entering the United States to uncover spies.


Keeler Model #6328

This model is a revision of the Keeler Model #6308. The first polygraph in the range included a GSR component and stimulus marker.


Keeler Model #6338

The #6338 was the final model produced by Associated Research and the first “Plethysmic Polygraph.” This device incorporated newly printed circuits and individually capped ink bottles. It stayed in service well into the 1970s, with some units making it into the 1980s and early 1990s, before the introduction of software to the polygraph industry.


Other Notable Polygraph Devices in History

While Keeler was the Father of the Modern Polygraph, several other companies produced devices worthy of mention. Here are the most notable polygraph devices in history besides those already mentioned.

  • Photopolygraph (1930) – Designed by W. Darow, manufactured by the Stoelting company.
  • Berkeley Polygraph Instrument (1938) – Developed by Captain Clarence Li from the Berkeley police.
  • Cardio-Numo Stoelting (1951) – A two-channel instrument developed by Clive Baxter.
  • Stoelting Model Deceptograph 22500 (1955) – Implemented in the US Army.
  • Stoelting-22600 Emotional Stress Monitor (1966) – A portable polygraph.
  • Lafayette model 76056 (1972) – The first polygraph instrument to use double pneumographs.
  • The Dektor Voice Stress Analyser (1973) – The first device to rely on voice stress analysis.
  • Stoelting Polyscribe (1974) – The first fully-electronic polygraph instrument.
  • Stoelting Ultrascribe (1979) – The successor to the Polyscribe instrument.


The Introduction of Software to Polygraph Science

The introduction of software and algorithms to polygraph science changed everything about the industry and how it conducted polygraph exams.

The first use of software in polygraphy came from a collaboration between Johns Hopkins University Applied Physics Laboratory, based in Maryland, and Axciton in 1989, with the project developing the “PolyScore” system.

After the success of PolyScore swept through the industry, several other manufacturers jumped on the bandwagon, leaving the Associated Research devices in the history books. Here are the top four players in modern polygraph software design and development.


Axciton Systems – The Modern Polygraph

Axiton Systems was the first company to launch polygraph software in a project collaborating with John Hopkins University. Axciton is the manufacturing brand behind “White Devagus-Despike” and “White Standard.” Their software has been used in public and private sector applications.


Stoelting Company – A Forerunner in Modern Polygraph Technology

Alongside Axciton Systems, Stoelting was one of the original innovators incorporating software into polygraph systems. Its first algorithm was launched in 1992, and today, Stoelting manufactures “CPSpro” software, the “gold standard” in polygraph software.


Lafayette Instruments – The Industry Leader

Lafayette Instruments is one of the big-four of polygraph software and instrumentation manufacturers. This company has the largest market share in the industry and works with private examination firms, government agencies, and military organizations around the world. The company’s “LXEdge” range of software and products promises to be the next big thing in polygraph science.


Limestone Technologies Inc.

This industry-leading form in polygraph technology experienced rapid growth and accumulation of market share in the 2000s. As a result, Lafayette acquired the company in 2022. Lafayette now owns its “Polygraph Pro” software and “Polygraph Professional Suite Version 3.0.


Where Will Polygraph Science Go Next? – AI & AVATAR

Polygraph technology experienced a leap with the introduction of software systems and computerized hardware in the 1990s. However, this innovation won’t end the technology’s progression in systems utilization.

The 2020s present the era of artificial intelligence; these systems are already in trial phases in polygraph devices. The US Department of Homeland Security and Canadian and EU authorities collaborated to develop and use the first AI-powered polygraph systems in the late 2010s.

AVATAR (Automated Virtual Agent for Truth Assessments in Real-Time), Was developed by research teams at San Diego State University and the University of Arizona. AVATAR utilizes AI technology in polygraph assessments, with its first application being an interactive video terminal to monitor immigrants at border crossings.

AVATAR asked immigrants if they were visiting the country or starting the immigration process. If AVATAR detected deception in the answers, it referred the applicant to screening with a US Border Patrol agent.

The system is so advanced that it can detect the use of countermeasures like tightening the leg muscles or curling the toes when answering questions. AVATAR evaluates immigrants by analyzing changes in eye movement, voice, gestures, and posture, determining if the interviewee is acting deceptively.

According to developers, AVATAR has up to an 80% success rate at detecting deception. As a result, border agents spend less time interviewing immigrants, conserving the organization’s resources. AVATAR shows the way in which polygraph science is moving, and who knows what the future holds.


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