Blog Post #4: Can a Machine Detect a Lie? The History, Impact and Controversy of the Polygraph

When most people hear the word "polygraph", the first thing that comes into mind are mostly related to crime shows, murder cases, or any other television show where a person is asked, "did you do it?" While the polygraph is typically known to the public as a "lie detector," its history and how it came to be the modern technology it is today is a lot more complex than most individuals realize. In fact, the polygraph was not originally invented to help aid in criminal cases. Over the past century, the polygraph has influenced criminal investigations, government employment, and public perceptions of truth. While also sparking continuous debates about science, privacy and ethics.  

From Medical Device to Lie Detector 

One of the most surprising facts I learned during my research is that the polygraph began as a medical device rather than a tool for criminal investigations. According to Theodora Burbank in The Origins of the Polygraph, "the original polygraph machine had nothing to do with lies and criminal investigation: it was actually a medical device" (Burbank, 2020). Scottish physician Dr. James Mackenzie developed the first ink-writing polygraph in the 1892 to monitor patients' heartbeats and study irregular heart rhythms. 

Mackenzie's invention used rubber tambour attached to a patients neck and wrist to record pulse patterns onto paper. At a time when physicians lacked effective methods for tracking heart activity, this technology represented an important breakthrough in medicine. Although the machine was eventually replaced by the electrocardiogram (EKG), its basic concept of recording physiological responses would later become the foundation for the modern polygraph. 

Later in 1895 Cesare Lombroso used the scientific instrument to measure physiological response. Lombroso modified an existing instrument called a hydrophygmograph and used it to measure physiological changes in the blood pressure and pulse of a suspect questioned by police. After Lombroso came William Moulton Marston, an American lawyer and psychologist credited with the invention of a basic form of the lie detector in 1915. Dr. Marston used a standard blood pressure cuff and a stethoscope to take intermittent readings of the systolic blood pressure of a subject during an interview to determine deception. 

The modern polygraph emerged in 1921 when John A. Larson, a Canadian psychologist working for the Berkeley Police Department built which many people consider the "original" lie detector. A device that measured several physiological responses at the same time. Using this polygraph Larson was the first person to measure and record continuously and at the same time the heart rate, blood pressure and respiratory changes of a person during interrogation. In 1939, Leonarde Keller patented what was considered the prototype of the modern polygraph (the Keeler Polygraph). Today Leonarde Keeler is known to be the father of the polygraph. 

Finally in 1993, the official entry of the polygraph into the modern age of technology happened when statisticians at John Hopkins University Applied Physics Laboratory in Maryland completed a software called Polyscore, which used a mathematical algorithm to analyze the polygraph data in order to estimate the probability level of lying or sincerity of a subject. This advancement helped standardize
the interpretation of polygraph results, reducing some of the subjectivity involved in human analysis and paving the way for the computerized polygraph systems that are commonly used today. 

How Does a Polygraph Work Today?

Opposite to popular belief, a polygraph doesn't actually detect lies. Alternatively, it measures physical responses that are linked to stress or anxiety. According to Jenifer González of the Law Library of Congress, "The modern polygraph records multiple physical measures simultaneously: respiration, heart rate, blood pressure, and sweat gland activity" (González, 2022).

A modern polygraph examination generally follows three stages: 

Step 1: Pre-Test Interview 

The examiner starts by explaining the process and reviewing the questions, which then establishes a baseline for the individuals physiological responses.

Step 2: Polygraph Examination 

The examinee is connected to sensors that monitor breathing, blood pressure, heart rate, and perspiration while answering a series of questions. These questions often include relevant questions, comparison questions, and neutral questions. 

Step 3: Analysis and Post-Test Interview 

The examiner reviews the physiological data and looks for significant reactions to particular questions. If unusual responses are detected, the examiner may conduct a follow-up interview.  

Today, polygraphs are commonly used by federal agencies such as the FBI, CIA, and NSA during employment screening and security clearance investigations. González notes that "the FBI require all applicants to pass a polygraph exam as part of the employment process" (González, 2022). While the results are often used as investigative tools, they are rarely considered conclusive evidence 

How the Polygraph Changed Communication 

With its creation, the polygraph revolutionized communication by showing how technology can measure honesty and reliability. Prior to the polygraph, investigators depended primarily upon verbal statements, witness testimony, and confessions. The design of this new device gave way to additional forms of communication based on the honesty and reliability of individuals through the use of physiological data instead of spoken or written expression alone. 

The device also influenced how society views honesty. Many people began believing that machines could determine truth more accurately than humans. This perception helped make the polygraph a powerful psychological tool. In some cases, suspects confess before the examination even begins because they believe that machine will expose deception. 

The polygraph's influence extends beyond law enforcement. It become a fixture in television, movies, talk shows, and true crime programs. Even people with little knowledge of criminal justice recognize the phrase "lie detector test." Through popular culture, the polygraph helped shape public beliefs about truth, deception, and trust 

The Controversy Surrounding Polygraphs 

Despite their popularity, polygraphs remain highly controversial. One major issue is that they do not actually detect lies, they detect physiological reactions. A person may show signs of stress because they are nervous, frightened, embarrassed, or simply uncomfortable being questions. Likewise, a deceptive person may remain calm and produce few noticeable physiological changes. 

This debate has existed almost since the invention of the machine. In Frye v. United States (1923), one of the first major court cases involving the polygraph, the court ruled that the technology had not gained sufficient scientific acceptance to be admitted as evidence. Nearly a century later, courts remain skeptical. 

In United States v. Scheffer (1998), Justice Clarence Thomas wrote that "to this day, the scientific community remains extremely polarized about the reliability of polygraph techniques" (González, 2022). Because of this uneasiness, many courts either prohibit polygraph evidence or allow it only under very limited circumstances. 

Researchers John Synnott, David Dietzel, and Maria Loannou also found that while polygraph often perform better than chance, they are far from perfect. Their research suggests that polygraph examinations may be useful investigative tools but should not be viewed as definitive proof of truth or deception. 

Why the Polygraph Still Matters

More than 100 years after its invention, the polygraph remains one of the most recognizable communication technologies in the world. What began as a device for studying heart rhythms evolved into a tool used by law enforcement agencies, intelligence organizations, and employers. It changed the way investigators gather information, influenced government security practices, and shaped public perceptions of honesty. 

At the same time, the polygraph raises important questions about privacy, scientific reliability, and the role of technology in determining credibility. Should an employer or government agency be able to determine an individuals honesty using objective data from a device? Is it even possible for a device to determine whether someone is telling the truth? While the answers to these questions may be impossible to know for certain, the history of the polygraph demonstrates how communication technologies can significantly shape both communication and society. Even though the machine may not always be able to "detect lies" the way the polygraph has influenced law enforcement, public trust and modern communication is undeniable. 

Sources 

Burbank, T. (2020). The Origins of the Polygraph. Warren Anatomical Museum. https://countway.harvard.edu/news/origins-polygraph 

González, J. (2022). To Tell the Truth: A Short History of the Polygraph. Law Library of Congress https://blogs.loc.gov/law/2022/11/to-tell-the-truth-a-short-history-of-the-polygraph/ 

Kelley Polygraphe | Brief History of the Polygraph. (n.d.) http://www.kellypolygraphe.com/polygraph-history.php

Synnott, J., Dietzel, D., & Loannou, M. (2015). A Review of the Polygraph: History, Methodology and Current Status. Crime Psychology Review. https://www.tandfonline.com/doi/full/10.1080/23744006.2015.1060080#d1e451