Berkeley Psychograph: History, Specs & Collector’s Guide

The Berkeley Tradition of Polygraph Innovation

The Berkeley Psychograph — also commonly known as the Lee Polygraph — was developed by Captain Clarence D. Lee, Chief of Detectives at the Berkeley Police Department in California [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s. Lee was the second member of the Berkeley Police group — after John Larson — to construct a polygraph instrument, beginning work in the 1920s [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy. His innovations built directly upon Larson's pioneering 1921 cardio-pneumo-psychograph, the first device to simultaneously and continuously record blood pressure, pulse, and respiration during questioning [3]Verified The Cardio-Pneumo-Psychograph (First Continuous Polygraph)
Confirms John A. Larson developed the first continuous polygraph recording device at the Berkeley Police Department in 1921.

The Berkeley Police Department had become a hotbed of forensic science innovation under its legendary police chief, August Vollmer. Vollmer was the first police chief of Berkeley, California, and has been described as "the father of modern policing" [4]Verified August Vollmer — Wikipedia
Confirms August Vollmer was the first police chief of Berkeley, California, described as 'the father of modern policing'. He promoted the use of new technologies such as fingerprinting, polygraph machines, and crime laboratories [5]Verified Vollmer, August — Encyclopedia.com
Confirms Vollmer promoted the use of fingerprinting, polygraph machines, and crime laboratories at the Berkeley Police Department, and it was his encouragement and support that led John Larson to develop the polygraph [6]Verified Major New Biography, Exhibit on August Vollmer — Berkeleyside
Confirms Vollmer's influence and support led John Larson to develop the polygraph and that protégés invented the lie detector. The modern polygraph was truly born in Berkeley, where Vollmer built a police department that served as a model of police professionalism [7]Verified The Polygraph Wars — Jim Fisher Forensic Science
Confirms the modern polygraph was born in Berkeley, California, under August Vollmer's leadership. To learn more about ancient lie detection methods, see our comprehensive guide.

Lee's Role in the Berkeley Polygraph Lineage

Lee's place in polygraph history is significant not only for his instrument design but also for his contributions to polygraph technique. Captain Lee was the first to introduce the use of the guilt complex control question and the first 'Control Test', which was later renamed the Pre-Test [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. These procedural innovations improved testing methodology alongside his hardware improvements.

Lee was also an early and persistent advocate of the Peak of Tension (POT) approach to polygraphy over the then-prevailing Relevant/Irrelevant (R/I) technique [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy. In the POT test, questions are asked in a recognised order and a guilty examinee is expected to show a pattern of responsiveness that increases as the correct alternative approaches and decreases when it has passed [9]Verified The Polygraph and Lie Detection — Appendix A: Questioning Techniques
Confirms the Peak of Tension test format where questions are asked in recognisable order and guilty examinees show increasing responsiveness. Lee's advocacy for this technique contributed meaningfully to the evolution of polygraph questioning methods. For more on the Berkeley polygraph tradition, see our guide to Keeler vs. Larson: The Rivalry Behind the Polygraph.

The Berkeley Police Department's Polygraph Pioneers

The Berkeley Police Department produced three of the most important figures in early polygraph history: John Larson, Clarence D. Lee, and Leonarde Keeler. The polygraph was invented in 1921 by John Augustus Larson, a medical student at the University of California, Berkeley, and a police officer of the Berkeley Police Department [10]Verified Polygraph — Wikipedia
Confirms the polygraph was invented in 1921 by John Augustus Larson at Berkeley, and the Berkeley Psychograph was developed by C.D. Lee in 1936. Larson developed the first continuous polygraph recording device under the guidance of Chief August Vollmer [3]Verified The Cardio-Pneumo-Psychograph (First Continuous Polygraph)
Confirms John A. Larson developed the first continuous polygraph recording device at the Berkeley Police Department in 1921.

Leonarde Keeler, who worked for the Berkeley Police Department while still in high school under Chief Vollmer [11]Verified Leonarde Keeler — Wikipedia
Confirms Keeler was a Berkeley high school student who worked for the Berkeley Police Department under Chief Vollmer, built upon Larson's and Lee's designs. Keeler submitted a patent application for his own device in 1925 [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy and later moved to Chicago in 1930 to work at Northwestern University's Scientific Crime Detection Laboratory [12]Verified A Comprehensive History of the Polygraph — Polygraph UK
Confirms Keeler moved to Chicago, added GSR in 1938, opened the first polygraph school in 1948, and details about Reid's CQT development. In 1938, Keeler further refined the polygraph when he added a third physiological measuring component — the psychogalvanometer — measuring changes in galvanic skin resistance during questioning [13]Verified History of Polygraph — Ohio Polygraph Services
Confirms Keeler added the psychogalvanometer in 1938, Keeler founded the first polygraph school in 1948, and Kircher and Raskin developed CAPS in 1988. Keeler opened the world's first polygraph school, the Keeler Polygraph Institute, in Chicago in 1948 [14]Verified Keeler Polygraph Institute — Ohio Polygraph Services
Confirms Leonarde Keeler founded the world's first polygraph school — the Keeler Polygraph Institute — in Chicago in 1948. For more on Keeler's instruments, see our Keeler Polygraph Instruments: History & Model Guide.

The Broader Polygraph Landscape of the 1930s–1950s

The Berkeley Psychograph entered the market during a pivotal era in polygraph development. The first polygraph was created in 1921, when Larson devised an apparatus to simultaneously measure continuous changes in blood pressure, heart rate, and respiration rate [15]Verified A Review of the Polygraph: History, Methodology and Current Status
Comprehensive review confirming the development of polygraph technology from Larson through Keeler, including the addition of GSR in 1938 based on Reverend Summers' work. By the 1930s, several competing instruments were available, including Keeler's portable polygraph and the Darrow Behavior Research Photopolygraph, developed solely for research experiments [10]Verified Polygraph — Wikipedia
Confirms the polygraph was invented in 1921 by John Augustus Larson at Berkeley, and the Berkeley Psychograph was developed by C.D. Lee in 1936.

John E. Reid developed the Control Question Technique (CQT) between 1945 and 1947, a major breakthrough in polygraph methodology that replaced Keeler's Relevant/Irrelevant question technique [16]Verified History of Polygraph — Ohio Polygraph Services (CQT)
Confirms the Reid Control Question Technique replaced the Relevant/Irrelevant technique as a major breakthrough in polygraph methodology. Cleve Backster later refined Reid's work in 1960 with the Zone Comparison Technique, which introduced concepts like psychological set and numerical scoring [17]Verified A Comprehensive History of the Polygraph — Backster Zone Comparison
Confirms Cleve Backster developed the Zone Comparison Technique in 1960, building upon Reid's CQT. These methodological advances occurred alongside hardware developments, creating an increasingly sophisticated field of psychophysiological deception detection. Our guide to Cleve Backster: Polygraph Pioneer & Primary Perception covers his remarkable contributions in detail.

Four Core Functional Units

The Berkeley Psychograph consists essentially of four units: (a) a chart drive or recording unit, (b) a pneumograph or respiration unit, (c) a cardiograph or pulse-blood pressure unit, and (d) a stimulus signal unit [18]Verified Polygraphy: Understanding Lie Detection — Scribd
Confirms the Lee Psychograph consists of four units: chart drive, pneumograph, cardiograph, and stimulus signal unit. This four-unit design provided a logical and practical division of instrument functions, making the Berkeley Psychograph straightforward to operate in the field.

The instrument was designed to be a compact, portable unit that encompasses a novel arrangement of rubber tambours and a manually operated stimulus key [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. The rubber tambours served as mechanical transducers, converting physiological pressure changes into pen deflections on the chart paper. Visible on the instrument are pens for recording respiration, blood pressure, pulse, and stimulus response changes [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles.

Key Design Innovations Over Larson's Instrument

Lee introduced several meaningful improvements over Larson's original cardio-pneumo-psychograph. His innovations included a sprocket drive for the movement of chart paper instead of Larson's smoked drum method and an improved means of converting blood pressure signals into a reliable tracing [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy. The sprocket-drive system ensured consistent chart paper speed, which was critical for accurate timing analysis of physiological responses.

The major difference between the Berkeley Psychograph and the earlier Keeler instruments was that the Berkeley Psychograph incorporated a new design in the pulse-blood pressure unit [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. This novel cardiovascular recording mechanism represented a distinct engineering approach to capturing blood pressure and pulse data during examination. The instrument also included a pressure cuff and hand bulb, along with a pneumograph tube for recording respiration changes [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles.

Portable Suitcase Form Factor

The Berkeley Psychograph was designed to be as portable as a suitcase [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s. This design philosophy reflected the practical needs of law enforcement agencies that needed to transport their instruments between facilities, courthouses, and field locations. The instrument was housed in a mahogany wood case with a leather carrying handle, measuring approximately 17 inches wide by 8.5 inches deep by 6 inches tall [19]Verified BERKELEY PSYCHOGRAPH Lie Detector Machine — Auction Listing
Confirms the Berkeley Psychograph in original mahogany case measuring approximately 17 x 8.5 x 6 inches with leather handle.

This compact form factor made the Berkeley Psychograph particularly appealing to smaller and mid-sized law enforcement agencies that may not have had dedicated examination rooms. The mahogany case provided both protection during transport and a professional appearance during use.

Two-Channel Recording System

The Berkeley Psychograph is a two-channel polygraph with an event marker [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s. It records respiration via a pneumograph channel and cardiovascular activity via a cardiograph channel, with these channels recorded simultaneously on moving graph paper [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s. The stimulus marker allowed examiners to denote the precise moment each question was asked, enabling accurate correlation between questions and physiological responses.

Unlike the Keeler Polygraph (from 1938 onward), the Berkeley Psychograph does not include a Galvanic Skin Response (GSR) channel. Keeler was the first to add the GSR channel in 1938, based on the work of Fordham University psychologist Reverend Walter G. Summers [15]Verified A Review of the Polygraph: History, Methodology and Current Status
Comprehensive review confirming the development of polygraph technology from Larson through Keeler, including the addition of GSR in 1938 based on Reverend Summers' work. The electrodermal channel was slow to be adapted to polygraph applications, largely due to problems in devising a method of producing a permanent recording and the difficulty in interpretation of the recordings [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy.

Physical Dimensions & Components

Based on surviving auction specimens, the Berkeley Psychograph in its original mahogany case measures approximately 17 inches wide by 8.5 inches deep by 6 inches tall [19]Verified BERKELEY PSYCHOGRAPH Lie Detector Machine — Auction Listing
Confirms the Berkeley Psychograph in original mahogany case measuring approximately 17 x 8.5 x 6 inches with leather handle. The instrument was delivered complete with pens, sensors, and chart paper [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s.

The instrument's accessories included a standard blood pressure cuff, a hand bulb for inflation, a pneumograph tube (chest strap) for recording respiration, ink pens for tracing physiological data on chart paper, and rolls of compatible graph paper. The sprocket-driven chart paper system was one of Lee's most practical innovations, ensuring consistent and reliable paper feed during examinations.

Pre-Test Setup & Subject Preparation

Operating the Berkeley Psychograph required the examiner to first attach physiological sensors to the subject. The pneumograph tube was strapped around the chest to record respiration, while the blood pressure cuff was placed on the upper arm and inflated using the hand bulb. The subject was then seated in a comfortable position, and the examiner ensured all recording pens were properly inked and making contact with the moving chart paper.

Captain Lee was the first to develop the pre-test procedure, originally called the 'Control Test' [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. This pre-examination interview allowed the examiner to gather background information, establish rapport, and calibrate the instrument to the subject's baseline physiological state. This innovation represented a significant methodological advancement that remains a fundamental component of modern polygraph examinations.

Testing Procedure & Chart Interpretation

During the actual examination, the examiner would ask questions in sequence while simultaneously operating the stimulus marker key to note each question's precise position on the chart. The instrument recorded continuous tracings of both respiration and cardiovascular activity on the moving graph paper.

Chart interpretation was performed by visual analysis of the ink tracings, comparing physiological responses to relevant questions against responses to neutral or control questions. Lee's advocacy for the Peak of Tension approach [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy meant that many examinations conducted with the Berkeley Psychograph likely employed this technique, wherein questions are arranged in a specific sequence designed to elicit progressively stronger responses as the critical item approaches. The polygraph examiner Richard O. Arther later built upon these foundational techniques.

Agencies That Used the Berkeley Psychograph

The Berkeley Psychograph was used by municipal, county, and state law enforcement agencies across the United States [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. Lee sold his Berkeley Psychographs from the 1930s into the 1950s [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s, and some units remained in active law enforcement service well beyond the production period. One documented example was an instrument used by the Abilene Police Department from 1955 through the 1970s [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles.

The instrument was used primarily on juveniles during the 1930s, as the conventional rules of evidence did not apply at that time [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. The Berkeley Psychograph was particularly popular among smaller to mid-sized agencies that needed reliable, cost-effective polygraph equipment, as it offered a more affordable alternative to the Keeler Polygraph line.

The Berkeley Psychograph in the Field

The instrument's portability — designed to be carried like a suitcase [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s — made it well-suited for field use in various locations. Law enforcement agencies could transport the Berkeley Psychograph to different jurisdictions, courthouses, or interrogation facilities as needed.

The 'Lee Polygraph' (the original, earlier model) was taken out of service around 1938, after Dr. Bril, a criminologist from New York City, developed his own instrument — a 'Brilograph' — which measured changes in skin resistance (GSR) [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. However, the improved Berkeley Psychograph model introduced in 1938 continued in production and use well into the 1950s, representing a significant evolution from Lee's earlier design. For context on polygraph use during the 1960s, see our dedicated guide.

Comparison with Keeler Polygraph Instruments

The key differences between the Berkeley Psychograph and Keeler Polygraphs are significant. The Berkeley Psychograph has two recording channels, while Keeler Polygraphs (from 1938 onward) have three, including the psychogalvanometer (GSR) channel [13]Verified History of Polygraph — Ohio Polygraph Services
Confirms Keeler added the psychogalvanometer in 1938, Keeler founded the first polygraph school in 1948, and Kircher and Raskin developed CAPS in 1988. The Berkeley Psychograph was developed and assembled by Captain C.D. Lee at Berkeley, while Keeler Polygraphs were manufactured by Associated Research, Inc. (ARI) in Chicago [20]Verified Polygraph — National Museum of American History (ARI/Keeler)
Confirms Associated Research, Inc. manufactured Keeler Polygraph instruments including the 6308 and Pacesetter series models. The Berkeley Psychograph featured a novel pulse-blood pressure unit design that distinguished it from earlier Keeler instruments [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles.

Keeler's instruments generally commanded higher prices and greater name recognition, partly because Keeler moved to Chicago in 1930 to work at Northwestern University's Scientific Crime Detection Laboratory [12]Verified A Comprehensive History of the Polygraph — Polygraph UK
Confirms Keeler moved to Chicago, added GSR in 1938, opened the first polygraph school in 1948, and details about Reid's CQT development and actively promoted his devices through high-profile cases and even a film appearance in 1948 [21]Verified Leonarde Keeler — Wikipedia (Film Appearance)
Confirms Keeler appeared in the 1948 film Call Northside 777 playing himself, contributing to the polygraph's popularity. For a comprehensive overview of Keeler's instrument line, see our Keeler Polygraph Instruments guide.

Comparison with Stoelting Instruments

The Stoelting Company of Chicago, which had been producing polygraph instruments since 1935, introduced the Deceptograph Model 22500 around 1955 [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. The Model 22500 contained three recording channels — cardio, pneumo, and GSR — and used vacuum tubes in its amplifier, requiring approximately thirty minutes of warm-up time before use [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles. It weighed approximately thirty-one pounds with accessories [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles.

By comparison, the Berkeley Psychograph was lighter, simpler, and purely mechanical — requiring no electrical power or warm-up time. However, its two-channel limitation meant it captured less physiological data than the three-channel Stoelting instruments. Today's modern systems such as the LX5000 and Stoelting CPS Elite represent dramatically advanced technology compared to any analog-era instrument.

Transition from Analog to Digital

The Berkeley Psychograph's production era ended in the 1950s [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s, though individual units continued in service for decades afterward. The broader polygraph field underwent a transformative shift during the 1980s when research was conducted on computerized polygraph at the University of Utah by Drs. John C. Kircher and David C. Raskin [22]Verified History of Polygraph — CAPS Development
Confirms Kircher and Raskin developed CAPS in 1988 at the University of Utah, incorporating the first diagnostic algorithm for polygraph data. In 1988, they developed the Computer Assisted Polygraph System (CAPS), which incorporated the first algorithm used for evaluating physiological data collected for diagnostic purposes [22]Verified History of Polygraph — CAPS Development
Confirms Kircher and Raskin developed CAPS in 1988 at the University of Utah, incorporating the first diagnostic algorithm for polygraph data.

CAPS was later replaced by the Computerized Polygraph System (CPS), which used a computer without the analog polygraph [23]Verified Fundamentals of Polygraph Practice — CAPS/CPS Reference
Confirms CAPS was replaced by CPS (Computerized Polygraph System), which used a computer without the analog polygraph. In 1992, the polygraph made its official entrance into the computer age [22]Verified History of Polygraph — CAPS Development
Confirms Kircher and Raskin developed CAPS in 1988 at the University of Utah, incorporating the first diagnostic algorithm for polygraph data. These digital systems could digitise, store, edit, and analyse physiological data using discriminant analysis to produce statements of probability of deception [24]Verified Computer Assisted Polygraph System (CAPS) — Polygraph UK Glossary
Confirms CAPS was developed by Raskin and Kircher at University of Utah, using discriminant analysis to produce probability of deception statements. Validated algorithms have exceeded 98% accuracy in quantifying physiological data from polygraph examinations administered in real criminal cases [25]Verified A Comprehensive History of the Polygraph — Algorithm Accuracy
Confirms validated algorithms have exceeded 98% accuracy in quantifying physiological data from polygraph examinations in real criminal cases. For a look at modern computerized systems, see our Limestone Technologies product guide.

The Employee Polygraph Protection Act & Industry Evolution

The Employee Polygraph Protection Act of 1988 (EPPA) is a United States federal law that generally prevents employers from using polygraph tests, either for pre-employment screening or during the course of employment, with certain exemptions [26]Verified Employee Polygraph Protection Act — Wikipedia
Confirms the EPPA of 1988 generally prevents employers from using polygraph tests for pre-employment screening or during employment, with certain exemptions. The EPPA prohibited private employers from using lie detector tests, thereby eliminating approximately 85 percent of the tests then being given [27]Verified Employee Polygraph Protection Act of 1988 — Office of Justice Programs
Confirms the EPPA prohibited private employers from using lie detector tests, eliminating 85% of tests then being given.

However, the law does not cover federal, state, and local government agencies [26]Verified Employee Polygraph Protection Act — Wikipedia
Confirms the EPPA of 1988 generally prevents employers from using polygraph tests for pre-employment screening or during employment, with certain exemptions, and law enforcement polygraph testing has continued to grow. Modern computerized polygraph instruments — such as the Lafayette LX6 and ParagonX systems and the Axciton computerized polygraph — record at least five physiological channels with digital data acquisition, representing a dramatic advancement over the Berkeley Psychograph's two analog channels. These digital systems made analog instruments like the Berkeley Psychograph technologically obsolete, though they remain valued as important historical artifacts.

Current Market Values

The Berkeley Psychograph is considered rare on the collector market, with far fewer surviving units compared to Keeler or Stoelting instruments. Current market values reflect this scarcity:

Working units with original accessories (pressure cuff, pneumograph tube, ink pens, chart paper) typically sell for $500–$2,500 depending on condition and completeness. Display-only units in presentable cosmetic condition range from $200–$600. Museum-quality specimens with documented provenance from a specific law enforcement agency command the highest prices and may exceed the typical range.

Authentication Guide

When evaluating a Berkeley Psychograph, collectors should look for several key identifying features. The instrument should be housed in a mahogany wood case with a leather carrying handle [19]Verified BERKELEY PSYCHOGRAPH Lie Detector Machine — Auction Listing
Confirms the Berkeley Psychograph in original mahogany case measuring approximately 17 x 8.5 x 6 inches with leather handle. The approximate dimensions should be 17 inches wide by 8.5 inches deep by 6 inches tall [19]Verified BERKELEY PSYCHOGRAPH Lie Detector Machine — Auction Listing
Confirms the Berkeley Psychograph in original mahogany case measuring approximately 17 x 8.5 x 6 inches with leather handle. Authentic units will feature the sprocket-drive chart paper system and rubber tambour arrangement characteristic of Lee's design [8]Verified 7 Fascinating Facts About Polygraph History — Polygraph Sales
Confirms the Berkeley Psychograph was introduced in 1938 in Chicago, developed by Captain Lee of Berkeley PD, details about its design, novel pulse-blood pressure unit, guilt complex control question, and use on juveniles.

Collectors should verify that the instrument contains both the pneumograph and cardiograph recording components, along with the manually operated stimulus key. Original accessories including the blood pressure cuff, hand bulb, pneumograph tube, ink pens, and compatible chart paper significantly increase the value and authenticity of a specimen.

Preservation & Display

For long-term preservation, the mahogany case should be kept in a climate-controlled environment to prevent warping or cracking. Rubber tambours and tubing components are particularly susceptible to deterioration over time and should be stored away from direct sunlight and extreme temperatures. Original ink pens and mechanical components should be kept clean and dry.

Museum-quality display should include informational plaques identifying the instrument's place in the Berkeley Police Department polygraph tradition alongside Larson's and Keeler's instruments. Provenance documentation — such as purchase records, department inventory tags, or examiner correspondence — greatly enhances both the historical and monetary value of any specimen.

A Bridge Between Pioneer and Professional Polygraphy

The Berkeley Psychograph occupies a unique place in the lineage of polygraph instruments — from the earliest physiological monitoring devices like Cesare Lombroso's hydrosphygmograph in 1895 [28]Verified Forensic Psychological Detection of Deception Standards
Confirms the Berkeley Psychograph was created by C.D. Lee in 1936 as a blood pressure-pulse-respiration recorder, and Lombroso's 1895 hydrosphygmograph use, through James Mackenzie's clinical ink polygraph in 1906 [29]Verified Sir James Mackenzie — History of Polygraph Instrumentation
Confirms Mackenzie refined his clinical polygraph in 1906 with watchmaker Sebastian Shaw, creating the clinical ink polygraph, William Marston's systolic blood pressure test in 1915 [15]Verified A Review of the Polygraph: History, Methodology and Current Status
Comprehensive review confirming the development of polygraph technology from Larson through Keeler, including the addition of GSR in 1938 based on Reverend Summers' work, Larson's continuous polygraph in 1921 [3]Verified The Cardio-Pneumo-Psychograph (First Continuous Polygraph)
Confirms John A. Larson developed the first continuous polygraph recording device at the Berkeley Police Department in 1921, and ultimately to the sophisticated computerized systems used today.

As one of the earliest practical field instruments designed by an active law enforcement professional, the Berkeley Psychograph demonstrated that reliable polygraph testing could be conducted by trained officers using relatively affordable, portable equipment. Lee's technical innovations — particularly the sprocket drive and improved blood pressure recording — solved real operational problems that examiners faced in the field. His advocacy for the Peak of Tension technique and his introduction of the control test concept [2]Verified Polygraph Development and People Behind — Educational Resource
Confirms C.D. Lee was the second Berkeley Police group member to construct a polygraph in the 1920s, details his sprocket drive innovation, improved blood pressure conversion, and POT advocacy had lasting impacts on polygraph methodology. To explore polygraph history in other countries, see our international coverage.

Historical Documentation & Scholarly Recognition

The comprehensive review by Synnott, Dietzel, and Ioannou (2015) in Crime Psychology Review documented the historical evolution of polygraph technology, including the contributions of the Berkeley Police Department pioneers [15]Verified A Review of the Polygraph: History, Methodology and Current Status
Comprehensive review confirming the development of polygraph technology from Larson through Keeler, including the addition of GSR in 1938 based on Reverend Summers' work. Paul V. Trovillo's definitive two-part history of lie detection (1939) in the Journal of Criminal Law and Criminology remains a standard reference that documents the transition from ancient truth-seeking methods to scientific instruments [30]Verified A History of Lie Detection (Parts I & II)
Definitive two-part history of lie detection from ancient China through modern polygraphy, standard historical reference. Walter G. Summers' 1938 work on lie detection history and methods provided an early comprehensive account documenting this pivotal era of development [31]Verified Lie Detection: Its History, Methods and Techniques
Early comprehensive account of lie detection history and methods, documenting the transition from ancient ordeals to scientific instruments.

The Berkeley Psychograph is formally documented in the PDD Terminology Reference maintained by the American Polygraph Association as a two-channel polygraph with event marker assembled by C.D. Lee of Berkeley [1]Verified Berkeley Psychograph (or Lee Polygraph) — PDD Terminology Reference
Confirms the Berkeley Psychograph was assembled by C.D. Lee of Berkeley, was a two-channel polygraph with event marker, delivered complete with pens and sensors, and sold from the 1930s into the 1950s. This official recognition ensures the instrument's place in the professional polygraph literature. For a broader perspective on how the APA's founding shaped polygraph standards, see our detailed account.