History of the Polygraph
The Donkey Knows (1500-1600)
In earlier times, village leaders often faced the challenge of determining who was lying about their involvement in a misdeed. One clever method involved having the villagers enter a donkey stall where the donkey’s tail had been secretly greased. The villagers were told that the donkey would kick only the guilty party when its tail was pulled. After each person claimed to have pulled the tail, the elders inspected their hands. If someone’s hands were clean, it revealed they had not actually pulled the greasy tail — and were therefore presumed guilty. This simple use of psychology and trickery served as an early form of lie detection.
Over time, more scientific approaches were developed — leading to the invention of the modern polygraph instrument.
The Kymograph (1840)
The kymograph was initially a mechanical and hydraulic device, invented by German physiologist Carl Ludwig in the 1840s, and found its first use as a means to monitor blood pressure. It basically consists of a revolving drum wrapped with a sheet of paper on which a stylus moves back and forth, recording perceived changes of phenomena such as motion or pressure. It was believed that when a person feared being detected in a lie, blood pressure variations occurred. This was the earliest form of making a permanent recording of attempts to conceal deception.
The Modern Polygraph (1992)
Today, the polygraph has been computerized and measures heart functions, breathing suppressions, electronic dermal activity, PLE, and countermeasure activity without cumbersome ink handling and endless rolls of paper. It also integrates audio and video via webcams and uses sophisticated scoring algorithms. When properly functioning and administered by a certified examiner using standardized techniques, the polygraph's accuracy is 93% to 95%. Today the polygraph is used in every western civilized country to determine the veracity of truth.
Pioneers of the Polygraph
Frye vs. US (D.C. Circuit Court 1923)
This landmark case involved James Alphonso Frye, accused of robbing and murdering a doctor. Frye agreed to plead guilty to first-degree murder in exchange for a dropped robbery charge. He later rescinded and went to trial for the murder, believing he could beat the charge in front of a jury. Frye's defense team introduced psychologist Dr. William Moulton Marston, who had discovered the systolic blood pressure deception test in 1915 and was eager to promote his test using the kymograph.
According to Marston, Mr. Frye's lawyers came to him, and he agreed to test the defendant gratis. Marston recalled, “I gave him a deception test in the district jail. No one could have been more surprised than myself to find that Frye's final story of innocence was entirely truthful!" His confession to the Brown murder was a lie from start to finish. The judge ruled that since Marston had tested Frye prior to trial, he could not demonstrate the kymograph in court. Ultimately, Marston's involvement in this case resulted in a jury verdict of second-degree murder, which indicates substantial doubt attributed to Marston and his blood pressure instrument.
The General Acceptance Rule
Though it is believed that the Frye vs. US case decision delivered a fatal blow to the admissibility of the polygraph test in trial court, today it is allowed in 23 states under the “general acceptance rule.” New Mexico and Ohio allow the routine use of the polygraph, regardless of opposing counsel. Under the general acceptance rule, a judge can allow results from the polygraph if both the prosecution and the defense agree to the test prior it to being administered, coupled with acceptance of the polygraph from the local scientific community.
The Modern Polygraph
John Augusta Larson (1892 -1965)
In 1921, a medical student named John Larson from the University of California invented the modern polygraph instrument, which was much more accurate in its results than the previous machine, the kymograph. It measured the subjects pulse, blood pressure, and respiratory rate, recording the information on a rotating drum of smoke paper. In 1925, Leonarde Keeler refined the instrument. Instead of using smoke paper to record changes in the suspects’ reactions, he incorporated ink pens in order to ensure the efficiency of the machine.
Leonarde Keeler (1903-1949)
Leonarde Keeler continued improving the kymograph, adding skin conductance recording to the instrument. Keeler called the device he created the “Emotograph,” and he was the first American to receive a patent on what is commonly known as the polygraph—or lie detector device. He invented the analog polygraph instrument that used tracing pens on a moving chart instead of cumbersome smoke paper on a drum. Keeler went on to found a polygraph school in Chicago, the Keeler Polygraph Institute (1948). Eventually John Reid, a Los Angeles police officer, would introduce questioning techniques to polygraphs that are still in use today.
Cleveland Grover Backster (1924-2013)
Cleveland (Cleve) G. Backster was a student of Leonarde Keeler, one of the earliest innovators of the polygraph, and served as an aide to a Navy admiral during World War II. After attracting the attention of the Central Intelligence Agency (CIA), Backster became its first polygraph examiner. According to accounts, he once hypnotized an admiral’s secretary and persuaded her to reveal top-secret war plans — a demonstration that showcased the power of psychological techniques in interrogation.
Backster later founded the Backster School of Lie Detection, where he trained generations of polygraph examiners. He is credited with developing the Zone Comparison Technique, a standardized method for conducting polygraph tests and objectively scoring results — an approach still widely used today. Often called the father of the modern polygraph, Backster also explored the frontier of bio-communication with his book Primary Perception, which detailed his controversial experiments on the emotional responses of plants to human thoughts and actions.
Primary Perception
Cleveland “Cleve” Backster’s discovery of bio-communication is detailed in his book Primary Perception. Although the book is out of print, it is still available through Amazon and other book resellers. It comes highly recommended for anyone interested in exploring his groundbreaking work.