There’s some controversy around polygraph science about exam results’ accuracy. Speak to technology advocates, and they’ll tell you the lie detector machine is up to 97% accurate at detecting deception. Detractors state it’s far lower than that, with test results showing accuracy rates between 50% to 70%.

So, who’s on the right side of history here?

This post gives you everything you need to know about polygraph accuracy. We’ll look into the history of lie detector machines and the progression of this science and give you the real answer on whether or not you can trust the examiner’s interpretation of your lie detector test.


The History of Polygraphy

The invention of the modern lie detector test comes from innovations in technologies created in the late 1800s. Many men are responsible for developing theories that introduced the invention of the first crude devices to detect deception in subjects under interrogation by law enforcement.

Criminologists, psychologists, and law enforcement officials like Marie Gabriel Romain Vigouroux, Cesare Lombroso, and Vittorio Benussi were the first to determine the relationship between vital signs, like blood pressure, and deception in the late 1800s.

However, a cardiologist named Dr. James MacKenzie invented the original “polygraph,” launching it in 1902. MacKenzie’s device had nothing to do with deception detection. Rather, it was involved in medical diagnosis, allowing the doctor to track the cardiovascular activity of his patients.

Dr. William Marston was the first American to create a lie detector test for deception detection in 1915. His invention, “The Systolic Blood Pressure Test,” formed the foundation for John A. Larson’s work on his “Sphggy” device that would become the first polygraph device used in law enforcement applications in 1921.


Are Polygraph Exams Accurate? – The Keeler Era

While Larson’s device was a true innovation in polygraph science, his friend, Leonard Keeler, advanced Larson’s designs, bringing about the modern polygraph with his invention of the “Emotograph” in 1925. Keeler went on to redevelop his design several times until his death in 1949 at the age of 45.

However, Keeler’s technology partner, “Associated Research,” a Chicago-based firm, went on to redevelop and release several versions of the “Keeler Polygraph” from the 1930s to the 1960s. These polygraph machines were considered the gold technology standard until the first software-based systems were released in the 1990s.


Are Polygraph Exams Accurate? – The Software Era

The issue was that the Keeler polygraph was estimated to be between 60% to 70% accurate at detecting deception in a lie detector test. Its electromechanical operation led to the invention of countermeasures designed to fool the test, and the device had a challenging time separating anxiety in subjects from deception.

This changed in the 1990s as Axciton Systems, and John Hopkins Laboratory released the “PolyScore,” the world’s first computerized polygraph device. Over the last three decades, we’ve seen algorithmic technology dominate the field, and device accuracy soared from 60% to 70% to 87% to 97%, depending on who you talk to.

According to the American Polygraph Association (APA), the world’s leading polygraph association in evidence-based scientific methodology for credibility assessment, the polygraph is 87% accurate at detecting deception. However, independent polygraph software developers, like Lafayette instruments, Stoelting, and Axciton Systems, state their software can produce 97% accuracy in test results.


When Do Employers Use Polygraph Exams?

The introduction of the “Employee Polygraph Protection Act of 1988” (EPPA) put an end to polygraph use in the workplace. Reagan signed the Act into power during his final weeks in office, which still stands today.

The Act came about due to the complaints received by the US labor Department from candidates and employees regarding their employer’s abuse of the lie detector in hiring and firing practices. As a result, the Act banned the use of polygraph exams in pre-employment screening in the private sector.

However, despite polygraphs being all but illegal for employers to use, the Act makes provisions for the use of pre-employment screening and random and specific employee testing in private sector applications. Some industries are exempt from complying with the Act, depending on their nature of business.

For instance, companies involved in high-risk industries, such as security, high-value asset transport and storage, and pharmaceutical manufacturing and distribution, may use the polygraph in hiring and firing employees.


Pre-Employment Screening

Polygraphs are useful for these high-risk industries in pre-employment screening practices. By polygraphing candidates, these companies can tell if the employee is acting deceptively under questioning to do harm to the company if hired. As a result, companies can prevent hiring bad actors and criminals that might damage the organization’s operations and reputation.


Random & Specific Testing

These high-risk industries may also initiate polygraph policies for their employees’ random and specific testing. However, the Act also provides provisions for those private sector companies operating outside of these high-risk industries. For example, if an employer experiences a severe economic theft at their company, they may use a polygraph policy to uncover the perpetrator of the crime.


Are Polygraph Exams Legal?

As mentioned, polygraphs are mostly illegal to use in the private sector. However, public sector organizations involved in national security operations, such as the CIA, FBI, and DOD, don’t have to comply with the EPPA legislation.

If a private sector employer uninvolved in a high-risk industry wishes to implement a polygraph policy, they must follow the guidelines of the EPPA or risk an investigation by the US Labor Department. To ensure they follow the guidelines of the EPPA, the employer must hire the services of a qualified attorney experienced in these matters.

The employer must also hire an independent polygraph company that appoints an examiner to assist the employer with setting up the polygraph policy and rolling it out to employees. Provided the employer has a valid reason to polygraph their team and follows the EPPA guidelines directed to them by their attorney and the examiner, they have the right to polygraph their team.

However, the employer has no right to enforce their polygraph policy on the workforce. If any employer refuses to participate in a lie detector test, the employer must comply with their wishes. The employer may not use the polygraph results or the employee’s refusal to undertake it to fire them from the organization or bully or intimidate them into leaving.


How Does the Polygraph Exam Work?

The polygraph exam is between 45 to 90 minutes long. It involves the examiner sitting alone with the employee or candidate in the room. They’ll ask the examinee a series of five to seven predetermined questions regarding the examinee’s reason for taking the test.

The questions require yes-or-no answers, and the examiner may not ask questions that pry into the examinee’s personal life or are outside of the predetermined questions set before the test. The examiners have the duty to make the employee feel comfortable before the test, and they must release the employee at any stage during the exam if they wish to end the polygraph and leave the room.


How Does the Polygraph Detect Deception?

The lie detector test doesn’t actually detect “lies” or when a person is telling the truth. It sees “deception” in the examinee’s answers by monitoring the body’s vital signs. We need insight into the nervous system and how it launches the “fight-or-flight” (FoF) response to understand how the polygraph works.


Understanding The Sympathetic Nervous System

The human nervous system consists of two primary branches – the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). Concerning the FoF, we’re interested in the PNS, particularly the “Sympathetic Nervous System” (SNS).

The SNS is part of the PNS and is responsible for launching the FoF.


Understanding the Fight-or-Flight Response

The FoF is a primal human response developed through our evolution. It’s thousands of years old, developed by our ancestors to help us escape predators. The FoF activates when we experience severe stress in our environment.

In the past, the FoF would activate if a predator charged us, hoping to turn us into its dinner. However, these threats don’t exist to us anymore. Modern humans experience stress through other means, such as work, relationships – or a lie detector test.

When stress reaches a specific level in the body and becomes overwhelming in the face of a threat, the SNS activates the FoF. The body and brain are already on red alert when sitting in the exam room. All it takes is the examiner to ask a question where your only option is to lie to save yourself, and the stress causes the SNS to activate the FoF.

The examiner notices the changes in your physiological response when the FoF launches. Your blood pressure and heart rate elevate, as does your breathing. Your skin sends electrical charges through it, and you start to sweat. The instrument attached to your body picks up these changes, relaying the data to the examiner.


Can I Beat a Polygraph Exam?

So, can you beat a polygraph? The answer is not likely. To do so, you would have to have control of the SNS and how it activates the FoF. Unfortunately for you, the FoF and SNS are “autonomous” systems. That means they launch without your conscious input.

So, you have no way of controlling it. The FoF activates, and the examiner picks it up immediately. They’ll know you’re hiding something and repeat the question to confirm the result. The FoF slightly diminishes each time you answer, but the examiner’s software notices it, giving them the information they need to classify your answer as deceptive.

Some internet forums and message boards discuss how to use “countermeasures” to beat the polygraph.


What are the Types of Countermeasures Used in Polygraph Exams?

Countermeasures are tactics examinees use during the lie detector test to interfere with the body’s ability to launch the FoF. People use several types of countermeasures, with common ones being biting the inside of the cheek, clenching their thigh muscles, controlling their breathing, or curling the toes.

They’ll execute the countermeasure as the examiner asks the question. In the past, the feedback of this countermeasure to the polygraph would lead to an “inconclusive” result. However, these countermeasures come from a time when the older types of polygraphs were used in the industry.

Today’s software polygraph systems can interpret if an examinee is using a countermeasure. The examiner has the experience to know when the examinee is attempting to use these countermeasures, and they’ll ask them if they’re using this strategy.

If the examinee is caught using a countermeasure, they immediately fail the exam. Today, a popular countermeasure is the use of Xanax or beta-blockers during the exam. These drugs suppress stress in the nervous system and might interfere with the launch of the FoF during the lie detector test.

However, a talented and experienced examiner can tell when the examinee uses a drug-based countermeasure and the examinee will fail the test.


Can The Lie Detector Tell the Difference Between Anxiety and Deception?

In the older days of polygraph technology, between the 1920s to the 1990s, the technology in lie detectors and the questioning systems used, particularly in law enforcement and intelligence operations, creating false positives in exam results.

One of the common complaints was that the machine couldn’t distinguish between someone nervous and someone displaying deceptive behavior. However, the modern polygraph can determine these differences.


The Defining Difference in Polygraph Accuracy – The Examiner

When you arrive in the exam room, the examiner does their best to make you feel at ease. They encourage you to research the polygraph before you take the exam. This approach helps you familiarize yourself with the polygraph process and how it works.

By learning about the exam and how it works, you reduce the fear of the unknown, and there’s less chance of being overly nervous when you enter the exam room. When you sit down for the test, the examiner will review your rights and what they’ll ask you during the exam. They expect you to be nervous and will ask you if you have any questions regarding the exam.

The examiner aims to make you feel comfortable during the test. Doing so reduces your anxiety around the situation and the chances of a false positive.