Leonarde Keeler: The Father of the Modern Polygraph Machine

Birth and Family Background

Leonarde Keeler was born on October 30, 1903, in North Berkeley, California, to a family steeped in intellectual and artistic life [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. His father, Charles Keeler, was a noted poet and naturalist with deep connections to the University of California academic community [2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. His mother was artist Louise Bunnell [2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. Charles Keeler chose his son's distinctive first name as an homage to the Italian polymath Leonardo da Vinci, reflecting the family's reverence for invention and the scientific arts [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930..

The elder Keeler was a close friend of August Vollmer, the pioneering Chief of Police at the Berkeley Police Department [3]Verified Biography of Leonarde Keeler
Documents Keeler's transformation of the polygraph from experimental apparatus to practical forensic tool, his establishment of the first polygraph school, and his role in landmark cases.. This connection would prove pivotal in shaping young Leonarde's career trajectory. Growing up in the vibrant intellectual atmosphere of early twentieth-century Berkeley provided Leonarde with an environment perfectly suited to nurture his curiosity about science and forensic investigation.

High School and Early Interests

Leonarde, who preferred his friends and associates to call him "Nard," attended Berkeley High School, where he developed a keen interest in stage magic and sleight of hand [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. This fascination with illusion and misdirection would prove oddly prescient — his later career would revolve around distinguishing truth from deception, albeit through scientific instruments rather than card tricks.

As a teenager, Leonarde suffered a serious illness that left him in a weakened condition [3]Verified Biography of Leonarde Keeler
Documents Keeler's transformation of the polygraph from experimental apparatus to practical forensic tool, his establishment of the first polygraph school, and his role in landmark cases.. During his convalescence, his father introduced him to the Berkeley Crime Detection Lab and to August Vollmer [3]Verified Biography of Leonarde Keeler
Documents Keeler's transformation of the polygraph from experimental apparatus to practical forensic tool, his establishment of the first polygraph school, and his role in landmark cases.. Vollmer was a legendary figure in American law enforcement reform, a visionary who was transforming the Berkeley Police Department into the most scientifically advanced police force in the country. Under Vollmer's mentorship, Keeler gained exposure to cutting-edge forensic methods and, critically, to the work of a young medical student named John Augustus Larson.

University Education

After graduating from Berkeley High School, Keeler enrolled at the University of California, Berkeley, in the fall of 1923 [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. His time at the university was shaped less by traditional classroom study than by his extracurricular work on polygraph development. After a short period at Berkeley, Keeler transferred to UCLA, following Vollmer when the police chief accepted a temporary appointment as Chief of Police in Los Angeles [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. He later transferred to Stanford University to study psychology under Professor Walter Miles [2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930., where he conducted experiments with early lie detection devices and honed the card-trick demonstration technique that would become his trademark [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. This academic journey — from Berkeley to UCLA to Stanford — underscored the depth of the mentor-protégé relationship between Vollmer and Keeler, a bond that would shape the young inventor's entire career.

Larson's Original Device

The story of the modern polygraph cannot be told without understanding the pivotal relationship between Leonarde Keeler and John Augustus Larson. Larson, a medical student and reserve officer at the University of California, developed the first continuous-recording polygraph instrument in 1921 [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.[5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. He called the device the "cardio-pneumo psychogram" [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.[5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph., and it represented a major leap forward from earlier, cruder attempts at physiological lie detection.

Larson's instrument simultaneously measured and recorded the examinee's blood pressure, pulse rate, and respiratory rate on a rotating drum wrapped in smoke paper [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.[5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. While the device was cumbersome and the smoke-paper recording method was fragile and difficult to preserve, it was the first instrument capable of continuously monitoring multiple physiological channels during interrogation — a fundamental advance over the discontinuous, single-variable measurements that preceded it [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph..

The first practical use of Larson's device came in the summer of 1921, when the San Francisco Call and Post arranged for Larson to test William Hightower, accused of murdering a priest [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. The young Keeler was introduced to Larson's work during his time at the Berkeley Police Department and was immediately captivated. While still a teenager, he began assisting Larson with his experiments, learning the principles of psychophysiological detection [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930..

A Collaboration That Changed History

Larson took Keeler on as an apprentice, recognizing the younger man's mechanical aptitude and tireless enthusiasm [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.. Together, they conducted numerous polygraph examinations at the Berkeley Police Department, refining their questioning techniques and learning how to interpret the physiological data the instrument produced. This hands-on experience was invaluable — it gave Keeler a practical understanding of the challenges facing polygraph examiners in the field and inspired the technical improvements he would later introduce.

However, the Keeler-Larson relationship was not without tension. The two men had fundamentally different visions for the polygraph's future. Larson viewed the device primarily as a scientific research tool, subject to the cautious rigor of academic inquiry [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. Keeler, by contrast, saw its potential as a practical law enforcement instrument and was eager to commercialize and popularize it [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. These differing philosophies would eventually drive a permanent wedge between mentor and protégé. For a deeper exploration of this dynamic, see our article on John Larson vs. Leonarde Keeler: The Polygraph Credit Dispute.

The Patent Controversy

One of the most consequential decisions in polygraph history was Larson's failure to file a patent for his polygraph device [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. Whether this was due to academic principle, oversight, or disinterest in commercialization remains debated by historians. Regardless of the reason, the vacuum created by Larson's inaction allowed Keeler to file his own patent, claiming intellectual property rights over his improved version of the instrument [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. This decision created a lasting rift between the two men and sparked a debate about credit and ownership that persists in polygraph historiography to this day. As historian Ken Alder wrote in The Lie Detectors, Keeler and Larson were "Vollmer's delinquent sons," each competing to control the future of the polygraph [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925..

The Systolic Blood Pressure Test

Before either Larson or Keeler entered the scene, the foundations of physiological lie detection had been laid by William Moulton Marston (1893–1947), a Harvard-trained attorney and psychologist [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. Marston believed that changes in systolic blood pressure during questioning could reliably indicate whether a subject was being deceptive. Using a stethoscope and a standard sphygmomanometer, he developed a discontinuous method of measuring blood pressure at key moments during an interrogation, which he first articulated around 1915 [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph..

Marston's method, while groundbreaking in concept, was laborious and impractical. The examiner had to manually inflate the cuff, take a reading, deflate it, ask a question, and then repeat the process [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. This discontinuous approach meant that brief, transient physiological reactions could easily be missed. Despite these shortcomings, Marston's work established the fundamental premise underpinning all subsequent polygraph development: the idea that deception produces measurable physiological changes [8]Verified From Ancient Oracles to Modern Techniques: The Evolution of Deception Detection
Documents how early deception detection methods established theoretical foundations for modern techniques including the polygraph..

It was Larson's reading of Marston's published work that inspired him to develop a more sophisticated, continuous-recording approach [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. And it was Keeler who would ultimately transform their collective insights into a commercially viable, practically useful device. The intellectual lineage from Marston through Larson to Keeler represents the core evolutionary path of modern polygraph technology.

Earlier Predecessors

Even before Marston, others had experimented with physiological measurement techniques that would inform lie detection. Sir James Mackenzie (1853–1925), the Scottish cardiologist, invented what he called a clinical "polygraph" — an ink-writing instrument for recording arterial and venous pulses to diagnose cardiac arrhythmias [9]Verified Sir James Mackenzie (cardiologist)
Confirms Mackenzie devised the clinical polygraph for recording arterial and venous pulses, with his ink polygraph used from the 1890s onward for cardiac diagnosis.. He described this device in his landmark 1902 text The Study of the Pulse [9]Verified Sir James Mackenzie (cardiologist)
Confirms Mackenzie devised the clinical polygraph for recording arterial and venous pulses, with his ink polygraph used from the 1890s onward for cardiac diagnosis.[10]Verified Mackenzie's Study of the Pulse and the Birth of the Polygraph
Provides context on Mackenzie's 1902 text The Study of the Pulse and his ink polygraph's influence on later polygraph instrument design.. Although Mackenzie's polygraph was a medical instrument designed to study heart function rather than detect deception, his ink-writing recording method directly influenced the design of later lie detection instruments — Keeler's replacement of smoke paper with ink pens was inspired by Mackenzie's ink polygraph system [10]Verified Mackenzie's Study of the Pulse and the Birth of the Polygraph
Provides context on Mackenzie's 1902 text The Study of the Pulse and his ink polygraph's influence on later polygraph instrument design..

Cesare Lombroso, the Italian criminologist, had used a hydrosphygmograph to measure blood pressure changes in criminal suspects as early as the 1890s [5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.. These early experiments, while primitive, established the theoretical groundwork on which Marston, Larson, and Keeler would build. For more on Mackenzie's contribution to polygraph history, see our dedicated article.

Replacing Smoke Paper With Ink Pens

Keeler's first major technical contribution to polygraph science came in 1925, when he replaced the cumbersome smoke-paper recording system used in Larson's instrument with ink pens [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. This seemingly simple change had profound practical implications. The smoke-paper method required the examiner to coat paper with a layer of soot, carefully mount it on a rotating drum, and then shellac the completed tracing to preserve it [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. This process was time-consuming, messy, and fragile — the tracings were easily smudged or destroyed.

By substituting ink pens that wrote directly on clean paper, Keeler dramatically reduced setup time, improved the permanence and legibility of the recordings, and made the instrument far more practical for use in the field [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. Keeler's ink-pen system drew inspiration from Sir James Mackenzie's ink polygraph, which had been used in medical science since the early 1900s [10]Verified Mackenzie's Study of the Pulse and the Birth of the Polygraph
Provides context on Mackenzie's 1902 text The Study of the Pulse and his ink polygraph's influence on later polygraph instrument design.. The ink-pen system also allowed for more precise, fine-grained tracings, making it easier for examiners to detect subtle physiological changes.

Adding Galvanic Skin Response

Perhaps Keeler's most scientifically significant innovation came in 1938, when he added a galvanic skin response (GSR) channel to his polygraph, based on the earlier work of Fordham University psychologist Reverend Walter G. Summers [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. Galvanic skin response, also known as electrodermal activity (EDA), measures changes in the electrical conductance of the skin caused by variations in sweat gland activity. When a person experiences emotional arousal — including the stress associated with deception — the sweat glands in the fingers and palms become more active, increasing the skin's electrical conductance.

The addition of GSR gave the Keeler Polygraph a critical additional physiological channel, alongside blood pressure, pulse rate, and respiration [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. This multi-channel approach significantly improved the instrument's diagnostic capabilities by providing examiners with additional, independent data points for evaluating deception. The GSR channel proved particularly valuable because electrodermal responses are largely involuntary and difficult for examinees to consciously control, making them a robust indicator of emotional arousal.

Today, the measurement of electrodermal activity remains a standard component of virtually all modern polygraph instruments, a direct legacy of Keeler's innovation [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. For those interested in how modern polygraph examinations are conducted, understanding this multi-channel approach — incorporating what is now measured through the polygraph cardiograph channel — is essential.

Portability and Commercial Viability

Beyond specific technical improvements, Keeler's overarching contribution was making the polygraph portable and commercially viable [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. Working with William Scherer of the Western Electro Mechanical Company, he designed an instrument compact enough to be encased in a mahogany travel box, allowing examiners to transport it easily to crime scenes, police stations, and courtrooms [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. August Vollmer famously described one of Keeler's early prototypes as looking like "a crazy conglomerate of wires, tubes, and old tomato cans" [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925., but the refined commercial version was a professional instrument that helped legitimize the device in the eyes of law enforcement and the public.

This portability was essential to the polygraph's adoption by law enforcement agencies across the country — an instrument confined to a university laboratory, no matter how sophisticated, would have had limited practical impact. As one historian noted, Keeler's goal was to turn Larson's delicate scientific apparatus "into a robust box that could be easily transported and was simple enough to use that even a cop — not some Ph.D. cop but just an ordinary cop — could use the device" [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. His device was purchased by the FBI and served as the prototype of the modern polygraph [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.[5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph..

Filing the First Patent

Keeler named his improved version of Larson's device "the Emotograph," reflecting its purpose of detecting emotional responses during questioning [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. He filed a patent application for the device on July 30, 1925, making it the first polygraph instrument to receive formal intellectual property protection in the United States [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[11]Verified Polygraph — National Museum of American History
Confirms U.S. Patent 1,788,484 (Jan. 13, 1931), Chicago Tribune obituary (Sept. 21, 1949, p. 30), and the Model 302C in the Smithsonian's collection.. The U.S. Patent Office approved the application on January 13, 1931, issuing U.S. Patent No. 1,788,484 for an "Apparatus for Recording Arterial Blood Pressure" [11]Verified Polygraph — National Museum of American History
Confirms U.S. Patent 1,788,484 (Jan. 13, 1931), Chicago Tribune obituary (Sept. 21, 1949, p. 30), and the Model 302C in the Smithsonian's collection..

The patent filing was significant for several reasons. First, it established Keeler's legal ownership of the technology, giving him the commercial rights to manufacture and sell polygraph instruments. Second, it provided a detailed technical description of the instrument's design, creating a public record that other inventors and manufacturers could study and build upon. Third, it cemented Keeler's claim to be the inventor of the modern polygraph — a claim that Larson would contest for the rest of his life.

The Fire and Reconstruction

Keeler's path to the patent was not without setbacks. In 1924, his first handmade prototype of the Emotograph was destroyed in a fire at his residence [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. It was at this point that August Vollmer intervened, introducing Keeler to William Scherer of the Western Electro Mechanical Company [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. Scherer, an experienced instrument maker, worked closely with Keeler to develop a new, improved version of the Emotograph.

Following Keeler's plans and written instructions, Scherer developed the rebuilt device with several advances over the lost prototype, including a motor drive for consistent paper speed, mechanical metal bellows for pneumatic measurement, and a pneumograph attachment that strapped around the examinee's chest to measure respiratory activity [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. The entire assembly was housed in a polished mahogany case, giving it both durability and an air of professional authority. The instrument also featured a mechanical indicator to mark the graph paper when a question was asked [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower..

First Mass Production and Public Demonstration

The partnership with Scherer also led to the first mass production of polygraph instruments [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. The Western Electro Mechanical Company successfully manufactured and sold the devices to police departments around the country [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. This was an extraordinary achievement for what was essentially a brand-new category of forensic equipment, and it demonstrated the strong demand for reliable deception detection tools among American law enforcement agencies.

Keeler gave the first public demonstration of his commercially manufactured polygraph on February 2, 1935 [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[12]Verified The Lie Detector Man: The Career and Cases of Leonarde Keeler
Confirms Keeler conducted the first admissible polygraph examination in court on February 2, 1935, in Portage, Wisconsin, resulting in criminal convictions., an event that attracted significant attention from law enforcement professionals and the press. He also showcased the machine at the 1933 Chicago World's Fair [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925., further boosting public awareness and institutional demand for the device.

A Romance Born in the Laboratory

Leonarde Keeler and Katherine Applegate were students at Stanford University when they met in 1925 [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.[13]Verified He Met His Wife Over a Lie Detector. Then Things Got Interesting.
Confirms Keeler and Applegate met at Stanford University in 1925, Katherine's role as handwriting analyst at the Northwestern crime lab, and biographical details.. Their initial connection was forged, fittingly, through the polygraph itself. During his college years, Keeler frequently demonstrated his lie detector prototypes on fellow students using his famous card trick. He would ask a subject to select a playing card from a deck, then hook the student up to the polygraph and ask them to deny picking any card as he went through the deck one by one [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925..

What Keeler's audiences often didn't know was that he sometimes rigged the deck, using his teenage expertise in stage magic to ensure the demonstration's success regardless of the instrument's actual performance. Katherine Applegate was the only student perceptive enough to see through his sleight of hand and challenge him on it [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. Her sharp intelligence caught Keeler's attention, and a friendship quickly developed that blossomed into romance.

Marriage and Shared Forensic Careers

The couple married in Chicago in 1930, the same year they relocated to the city [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[13]Verified He Met His Wife Over a Lie Detector. Then Things Got Interesting.
Confirms Keeler and Applegate met at Stanford University in 1925, Katherine's role as handwriting analyst at the Northwestern crime lab, and biographical details.. Katherine was no passive companion — she trained as a forensic investigator and became the nation's first female handwriting analyst [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[13]Verified He Met His Wife Over a Lie Detector. Then Things Got Interesting.
Confirms Keeler and Applegate met at Stanford University in 1925, Katherine's role as handwriting analyst at the Northwestern crime lab, and biographical details.. She later established her own all-woman's detective agency in Chicago, specializing in forensic investigation [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[13]Verified He Met His Wife Over a Lie Detector. Then Things Got Interesting.
Confirms Keeler and Applegate met at Stanford University in 1925, Katherine's role as handwriting analyst at the Northwestern crime lab, and biographical details.. The couple shared a deep commitment to forensic science, and their professional lives were closely intertwined during their years in Chicago.

At the Scientific Crime Detection Laboratory at Northwestern University, the Keelers became two of the lab's leading criminologists — Leonarde as its lie detection specialist, Katherine as an expert handwriting analyst [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. Their work together attracted considerable press attention, and spending time with them always involved what Keeler's sister Eloise described as talk of forensic specimens, handwriting samples, and criminal cases [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925..

Separation and Tragedy

Despite their shared passions, the marriage did not endure. Katherine eventually divorced Keeler and married Major René Alexander Dussaq [13]Verified He Met His Wife Over a Lie Detector. Then Things Got Interesting.
Confirms Keeler and Applegate met at Stanford University in 1925, Katherine's role as handwriting analyst at the Northwestern crime lab, and biographical details.[14]Verified René Alexander Dussaq
Confirms Dussaq was born May 6, 1911, in Buenos Aires, educated in Geneva, father was a Cuban diplomat, and served in the 101st Airborne Division.. Dussaq was born in Buenos Aires, Argentina, to a Cuban diplomat father, and was schooled in Switzerland before moving to Cuba [14]Verified René Alexander Dussaq
Confirms Dussaq was born May 6, 1911, in Buenos Aires, educated in Geneva, father was a Cuban diplomat, and served in the 101st Airborne Division.. He became an adventurer, Hollywood stuntman, and later a distinguished wartime operative with the Office of Strategic Services (OSS), serving as a major in the 506th Parachute Infantry Regiment of the elite 101st Airborne Division [14]Verified René Alexander Dussaq
Confirms Dussaq was born May 6, 1911, in Buenos Aires, educated in Geneva, father was a Cuban diplomat, and served in the 101st Airborne Division.[15]Verified Katherine Applegate Keeler Dussaq
Confirms Katherine Dussaq was one of 38 WASPs killed in service, died November 26, 1944 near New Carlisle, Ohio, entered WASP training August 9, 1943, and received the Congressional Gold Medal.. He received the Distinguished Service Cross and two Purple Hearts [15]Verified Katherine Applegate Keeler Dussaq
Confirms Katherine Dussaq was one of 38 WASPs killed in service, died November 26, 1944 near New Carlisle, Ohio, entered WASP training August 9, 1943, and received the Congressional Gold Medal..

Katherine joined the Women Airforce Service Pilots (WASPs) during World War II, entering flight training at Avenger Field, Sweetwater, Texas on August 9, 1943 [15]Verified Katherine Applegate Keeler Dussaq
Confirms Katherine Dussaq was one of 38 WASPs killed in service, died November 26, 1944 near New Carlisle, Ohio, entered WASP training August 9, 1943, and received the Congressional Gold Medal.. She graduated on February 11, 1944 [15]Verified Katherine Applegate Keeler Dussaq
Confirms Katherine Dussaq was one of 38 WASPs killed in service, died November 26, 1944 near New Carlisle, Ohio, entered WASP training August 9, 1943, and received the Congressional Gold Medal.. Tragically, on the night of November 26, 1944, Katherine was killed when the AT-6 she was flying on an administrative cross-country flight crashed near New Carlisle, Ohio [15]Verified Katherine Applegate Keeler Dussaq
Confirms Katherine Dussaq was one of 38 WASPs killed in service, died November 26, 1944 near New Carlisle, Ohio, entered WASP training August 9, 1943, and received the Congressional Gold Medal.. She was one of 38 WASPs killed in service to their country [15]Verified Katherine Applegate Keeler Dussaq
Confirms Katherine Dussaq was one of 38 WASPs killed in service, died November 26, 1944 near New Carlisle, Ohio, entered WASP training August 9, 1943, and received the Congressional Gold Medal..

The dual blow of Katherine's departure and her death sent Keeler into a spiral of depression from which he never fully recovered. He increased his drinking and smoking, and his health deteriorated rapidly [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. On September 20, 1949, Leonarde Keeler died in Door County, Wisconsin, after suffering a stroke [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. He was just 45 years old. His premature death robbed the field of polygraph science of its most dynamic champion at the height of the instrument's growing influence.

The 1935 Portage, Wisconsin Trial

One of the most significant moments in polygraph history occurred on February 2, 1935, when Keeler used his polygraph in the criminal trial of Tony Grignano and Cecil Loniello in Portage, Wisconsin [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.[12]Verified The Lie Detector Man: The Career and Cases of Leonarde Keeler
Confirms Keeler conducted the first admissible polygraph examination in court on February 2, 1935, in Portage, Wisconsin, resulting in criminal convictions.. The two men stood accused of the attempted murder of a sheriff, and all of the evidence was circumstantial [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. The judge had sought out the polygraph test because of the technology's impressive showing at the 1933 Chicago World's Fair police exhibit [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925..

Both sides agreed to allow the test — the defendants saw little to lose, and the prosecution was armed with only circumstantial evidence [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. Keeler strapped his device to each man's chest and arm, and the physiological results revealed not only that both men were likely lying, but suggested each man's specific role in the crime [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. On the stand, Keeler was measured in his claims, telling the judge he "wouldn't want to convict a man on the grounds of the records alone" [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. He estimated the polygraph's accuracy at about 75 percent [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925..

After Grignano and Loniello were convicted, Keeler's confidence swelled. He told the press that the verdict meant "the findings of the lie detector are as acceptable in court as fingerprint testimony" [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. This landmark case marked the first time polygraph evidence directly influenced a criminal conviction in an American court [12]Verified The Lie Detector Man: The Career and Cases of Leonarde Keeler
Confirms Keeler conducted the first admissible polygraph examination in court on February 2, 1935, in Portage, Wisconsin, resulting in criminal convictions., establishing a precedent that would shape debates about polygraph admissibility in court for decades to come.

The Loomis Murder Case (1937)

In 1937, Keeler applied his polygraph in connection with the murder of five-year-old Roger William Loomis in Lombard, Illinois [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. The subject of the polygraph examination was Grace Yvonne Loomis, the child's mother [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. This case demonstrated the expanding scope of polygraph applications, extending beyond robbery and assault cases into deeply sensitive family crimes. The case attracted significant attention in the Chicago area and further cemented Keeler's reputation as the nation's foremost polygraph authority.

The Cleveland Torso Murders (1938)

In 1938, Keeler conducted a polygraph test on Dr. Francis Sweeney, the chief suspect in the notorious Cleveland Torso Murders [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. Sweeney failed to pass the test, leading many — including the legendary detective Eliot Ness — to believe that he was the culprit [16]Verified Keeler, Leonard
Confirms Keeler tested Dr. Sweeney in the Cleveland Torso Murders with Eliot Ness, tested suspects in the Theresa Foster case, and appeared in Call Northside 777.. However, due to insufficient physical evidence, Sweeney was never formally charged with the killings [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. This case illustrated both the power and the limitations of polygraph evidence: while the instrument could identify likely deception, it could not substitute for the kind of physical evidence courts required for conviction.

German POW Examinations in Rhode Island

During World War II, the U.S. Army Criminal Investigation Division used Keeler to polygraph German prisoners of war incarcerated in the United States to determine which were sufficiently free of Nazi ideology to be repatriated as police officers in post-war Germany [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.[17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. According to Leonard Harrelson, Keeler's close friend and later director of the Keeler Polygraph Institute, Keeler used his original Western Electro Mechanical Company prototype for these examinations at Fort Getty, Rhode Island, in 1944 [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. This wartime application demonstrated the polygraph's versatility beyond criminal investigation and foreshadowed its later widespread use in government security screening, including programs that would eventually extend to the FBI and other federal agencies.

Northwestern University's Crime Lab

In 1929, civic leaders in Chicago — then known as "Murder City" for its staggering homicide rates — established the Scientific Crime Detection Laboratory at Northwestern University, the country's first formal institution for criminal investigation [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. Keeler moved to Chicago in 1930 to work at the laboratory and ultimately became the head of the crime lab in 1936 [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.. He held that position until 1938, when he entered private business [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details..

During his tenure, lie detection became the Northwestern lab's most lucrative department within just two years [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.. Keeler tested over a thousand bank tellers and department store clerks during his first two years in Chicago [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925., pioneering the use of polygraph examinations for employee screening. Records made and filed in Keeler's office over the course of his career covered more than 30,000 cases [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. For more on the laboratory's remarkable history, see our article on Fred Inbau's Legacy and the Chicago School of Forensic Science, and how Chicago became the birthplace of modern polygraphy [18]Verified Chicago: Birthplace of Modern Polygraphy
Confirms Chicago served as the birthplace of modern polygraphy through the development of standardized examination techniques and professional practices..

Founding the Keeler Institute

In 1938, Keeler left Northwestern to establish the Keeler Institute in Chicago, the first dedicated school for training polygraph examiners in the United States [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. The institute specialized in polygraph sciences, working closely with law enforcement operations and the private sector. Keeler himself worked as the nation's first full-time private polygraph consultant for the institute until his passing in 1949 [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details..

The Keeler Institute trained generations of examiners who went on to shape the field, including Cleve Backster, who became the CIA's first polygraph examiner and later developed the Zone Comparison Technique [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.. Leonard H. Harrelson (1924–2004) became the director of the Keeler Polygraph Institute and ran it from 1955 until his retirement [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.[19]Verified Once Secret CIA Report on Polygraph Luminaries
Confirms Leonard H. Harrelson (1924-2004) ran the Keeler Polygraph Institute from 1955 until his retirement and received the Leonarde Keeler Award in 2003.. Graduates of the institute like Lynn Marcy went on to standardize polygraph use across police departments. John E. Reid, another key figure who developed the control question technique and the Reid Technique of interrogation, was also deeply influenced by the Chicago polygraph community that Keeler helped create.

Keeler's Hollywood Appearance

Keeler's prominence in forensic science was even documented in popular culture. He appeared as himself in the 1948 film noir docudrama Call Northside 777, starring James Stewart, Richard Conte, and Lee J. Cobb [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. The movie was based on the true story of the questionable conviction of Joe Majczek for the murder of a police officer in 1932, and Keeler's role in the case [16]Verified Keeler, Leonard
Confirms Keeler tested Dr. Sweeney in the Cleveland Torso Murders with Eliot Ness, tested suspects in the Theresa Foster case, and appeared in Call Northside 777.. His appearance in a major Hollywood production reflected the extraordinary public fascination with polygraph technology during the late 1940s and cemented his status as the most recognizable figure in American lie detection.

Model #301: The First Manufactured Keeler Polygraph

The first advancement of Keeler's original design was the Model #301, which replaced his second polygraph design from 1925 [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. This was the first polygraph instrument manufactured for Keeler by Associated Research, Inc., a Chicago-based firm established in 1936 by James F. Inman [11]Verified Polygraph — National Museum of American History
Confirms U.S. Patent 1,788,484 (Jan. 13, 1931), Chicago Tribune obituary (Sept. 21, 1949, p. 30), and the Model 302C in the Smithsonian's collection.[17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. The Model #301 served the polygraph community for over two decades and established the basic design language that would characterize Keeler instruments for generations.

Model #302: Adding the Third Channel

The Model #302 was introduced in the 1950s and added a third channel — the "psychogalvanometer" — to the Keeler instrument [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. Manufactured by Associated Research of Chicago, the #302 utilized seven batteries along with an AC power source [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. It was housed in a steel case with a wrinkle finish and chromium trim [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. The cover attached to the case using slip hinges, allowing its easy removal at the testing site. A synchronous motor powered the chart drive unit at speeds of either six or twelve inches per minute [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. The #302 featured four recording pens — the longer pen recording electrodermal variations, the smaller pens monitoring blood pressure, respiration, and stimulus markers [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. The Keeler Model #302 had two modifications: the Model 302B and Model 302C [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. One Model 302C is now in the collection of the National Museum of American History at the Smithsonian Institution [11]Verified Polygraph — National Museum of American History
Confirms U.S. Patent 1,788,484 (Jan. 13, 1931), Chicago Tribune obituary (Sept. 21, 1949, p. 30), and the Model 302C in the Smithsonian's collection..

Model #6338: The Pacesetter Series

The Keeler Polygraph Model #6338 represented the culmination of decades of refinement [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. Weighing twenty-four pounds and measuring 18" × 11" × 6", it incorporated newly designed printed circuits and a new inking system where the pens were fed from removable, individually capped ink bottles with colored ink available [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. The newly designed vent valves featured a positive lock to prevent leaks [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. The Model #6338 retailed for $2,325.00 and remained in service through the early 1960s [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. Three different traveling cases were available, conforming to Federal Aviation requirements for air transport at the time [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases..

Preserving the Original Instrument

The American Polygraph Historical Society was gifted what is believed to be the prototype of the Western Electro Mechanical Company's first polygraph, built for Keeler by William Scherer [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. Over time, Keeler replaced it with many new instruments but saved it for posterity. He gave it to Leonard Harrelson, who became Keeler's confidant and director of the Keeler Polygraph Institute [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.[19]Verified Once Secret CIA Report on Polygraph Luminaries
Confirms Leonard H. Harrelson (1924-2004) ran the Keeler Polygraph Institute from 1955 until his retirement and received the Leonarde Keeler Award in 2003.. Harrelson presented the device to the APHS in 1996 for preservation [17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.. Though ravaged by time, the prototype instrument — lacking any faceplate or markings that production instruments would have included — stands as a tangible connection to the birth of modern polygraphy.

Impact on Modern Polygraphy

Since his death in 1949, no one in the polygraph field has fully taken Leonarde Keeler's place [3]Verified Biography of Leonarde Keeler
Documents Keeler's transformation of the polygraph from experimental apparatus to practical forensic tool, his establishment of the first polygraph school, and his role in landmark cases.. His innovations — the ink recording system, the addition of galvanic skin response, the portable design, the commercial manufacturing model, and the establishment of formal examiner training — collectively transformed polygraph technology from an academic curiosity into a practical forensic tool [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.[6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. The Keeler Polygraph was the first to be purchased by the FBI and served as the prototype for the modern polygraph used in law enforcement, intelligence, and government screening [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.[5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph..

Keeler's legacy extends beyond technology to methodology. He pioneered the Searching Peak of Tension format and refined interrogation techniques that influenced subsequent practitioners like John E. Reid, whose comparison question technique would further evolve the field [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.. The American Polygraph Association, founded after Keeler's death, carries forward many of the professional standards and practices that Keeler first championed.

Modern research continues to build on the physiological foundations Keeler established. Contemporary studies exploring machine learning approaches to deception detection still rely on the same core physiological modalities — cardiovascular, respiratory, and electrodermal activity — that Keeler integrated into his instrument [20]Verified Deception Detection with Machine Learning: A Systematic Review
Of 81 reviewed studies, detection accuracy ranged from 51% to 100%, with 19 works achieving above 90% accuracy, demonstrating the ongoing relevance of physiological deception detection.[21]Verified A Multimodal Polygraph Framework with Optimized Machine Learning for Robust Deception Detection
Demonstrates improved generalization through machine learning approaches to physiological data fusion — building on the multi-channel approach Keeler pioneered.. While the technology has evolved dramatically, the fundamental multi-channel approach Keeler pioneered remains at the heart of polygraph science.

Leonarde Keeler: A Chronological Overview

1903 — Born October 30 in North Berkeley, California, to Charles Keeler (poet/naturalist) and Louise Bunnell (artist) [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.

1921 — John Larson develops the cardio-pneumo psychogram at the University of California, Berkeley [4]Verified John Augustus Larson
Confirms Larson invented the cardio-pneumo psychogram in 1921, his work at the Berkeley Police Department under Vollmer, and the first practical use on William Hightower.[5]Verified Polygraph
Confirms Keeler made the polygraph portable, added GSR, and that his device was purchased by the FBI as the prototype of the modern polygraph.

1923 — Keeler enrolls at the University of California, Berkeley; later follows Vollmer to UCLA and transfers to Stanford University [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[2]Verified Finding Aid to the Leonarde Keeler Papers, 1899-1972
Confirms Keeler attended UC Berkeley, UCLA, and Stanford University to study psychology; married Katherine Applegate in 1930.

1924 — Keeler's first handmade Emotograph prototype destroyed in a fire at his residence [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.

1925 — Files U.S. patent application for an "Apparatus for Recording Arterial Blood Pressure" on July 30; replaces smoke paper with ink pens [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[11]Verified Polygraph — National Museum of American History
Confirms U.S. Patent 1,788,484 (Jan. 13, 1931), Chicago Tribune obituary (Sept. 21, 1949, p. 30), and the Model 302C in the Smithsonian's collection.

1925 — Meets Katherine Applegate at Stanford University [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.

1929 — Scientific Crime Detection Laboratory established at Northwestern University in Chicago [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.

1930 — Moves to Chicago; marries Katherine Applegate; joins Northwestern's crime lab [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.

1931 — U.S. Patent No. 1,788,484 approved on January 13 [11]Verified Polygraph — National Museum of American History
Confirms U.S. Patent 1,788,484 (Jan. 13, 1931), Chicago Tribune obituary (Sept. 21, 1949, p. 30), and the Model 302C in the Smithsonian's collection.

1933 — Showcases the Keeler Polygraph at the Chicago World's Fair [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.

1935 — February 2: First courtroom use of polygraph evidence in State v. Loniello and Grignano, Portage, Wisconsin [7]Verified The Truth, the Whole Truth, and Nothing But
Confirms the Portage trial details including defendants Grignano and Loniello, the attempted murder charge, and Keeler's 75% accuracy claim. Also confirms Keeler and Applegate met at Stanford in 1925.[12]Verified The Lie Detector Man: The Career and Cases of Leonarde Keeler
Confirms Keeler conducted the first admissible polygraph examination in court on February 2, 1935, in Portage, Wisconsin, resulting in criminal convictions.

1936 — Becomes head of the Scientific Crime Detection Laboratory at Northwestern [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.

1937 — Polygraphs Grace Yvonne Loomis in the murder investigation of her five-year-old son Roger William Loomis [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.

1938 — Adds galvanic skin response (GSR) channel to the polygraph; leaves Northwestern to found the Keeler Institute [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.

1938 — Tests Dr. Francis Sweeney, chief suspect in the Cleveland Torso Murders [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.

1944 — Polygraphs German POWs in Rhode Island to screen for post-war police service [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.[17]Verified Polygraph Museum Collection and History
Confirms Leonard Harrelson, the APHS donation in 1996, Fort Getty POW examinations in 1944, Model #302 and #6338 specifications, pricing ($2,325), and FAA-compliant travel cases.

1946 — Creates periodic screening program for the Atomic Energy Commission at Oak Ridge [6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.

1948 — Appears as himself in the film Call Northside 777 [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.[6]Verified A Review of the Polygraph: History, Methodology and Current Status
Confirms Keeler added GSR in 1938 based on the work of Reverend Walter G. Summers, made the device portable, patented it, and founded a polygraph school.

1949 — Dies September 20 in Door County, Wisconsin, at age 45 [1]Verified Leonarde Keeler
Confirms key biographical details: birth in 1903, death in 1949, marriage to Katherine Applegate, Emotograph fire in 1924, Portage trial 1935, Loomis case 1937, Sweeney case 1938, and WASP details.