The polygraph changed how law enforcement handled interrogations in the early 1900s. With over a century of development going into the device, it’s a technological marvel. When John Larson and Leonard Keeler perfected the polygraph, they had no idea how their creation would evolve over the decades.

What started as an electro-mechanical device is now a computer-driven system governed by machine learning and algorithms. According to experts, the polygraph is 97% accurate at detecting deceptive behavior in examinees. That’s an impressive feat.

However, the legacy of polygraphy and its progression to the modern era came with controversy. There are plenty of instances in the past showing the inaccuracies of earlier versions of the device.

Polygraphy science does have some limitations, it’s not an infallible technology, and there’s always room for improvement. After all, even though 97% accuracy sounds impressive, the detractor will always ask questions about the lagging 3%.

This post examines these limitations and how they affect the application of polygraph technology in law enforcement and public and private-sector applications.


The Polygraph – Industry Applications and Limitations of Use

Polygraph exams have several applications across many industries, from questioning sex offenders to verifying winners of fishing competitions and identifying fraudulent insurance claims. Polygraph exams are considered accurate, and many industries use them.

In law enforcement, the lie detector test assists with questioning terrorists, interrogating murder suspects, and other heinous crimes. Both local and state law enforcement institutions utilize the polygraph in this regard, and it’s a mainstay in government organizations like the CIA, FBI, DOD, and others.

For example, the US Border Patrol uses the polygraph to question immigrants they feel may threaten US national security. The polygraph acts as a barrier of protection, ensuring these organizations don’t make mistakes that could compromise the safety of Americans.

The private sector operates under a different ruleset for polygraph usage than government and public-sector organizations. The Employee Polygraph Protection Act of 1988″ (EPPA) determines how organizations can implement polygraph tests in the workplace.

Private sector employers may not use polygraph policies in employment pre-screening or in random and specific employee testing. However, there are some loopholes to the EPPA. For instance, this rule doesn’t apply to certain industries.

Those companies involved in high-risk industries, such as security, armed guarding, High-value asset transport and storage, and pharmaceutical manufacturing and distribution, are exempt from the EPPA. That means they can implement polygraph testing on employees and employment candidates.

For example, a pharmaceutical company may wish to pre-screen candidates for positions using a polygraph. This practice allows them to weed out candidates with drug habits that may abuse their position or those involved in distribution that may use their authority to involve crime syndicates in robberies.

The EPPA also provides room for private sector companies to institute polygraph policies in various circumstances that might affect the company’s operations or sustainability. For example, if the company experiences a large inventory theft. If an employee accuses a colleague of sexual harassment, management suspects drug abuse in the workplace, or financial fraud, they may implement a polygraph policy.


What are the Limitations of the Use of the Polygraph in Exam Scenarios?

The polygraph also has limitations on what it can achieve in exam scenarios. The lie detector test involves the examiner hooking up instrumentation to the examinee and connecting it to their computer, where a software program monitors the changes in the examinee’s vital signs.

The system monitors changes in blood pressure, heart rate, respiration, and skin and sweat activity during the questioning process. Essentially, the tools look for activation of the “fight-or-flight” response (FoF). The FoF is an autonomous system and part of the “sympathetic” nervous system. It’s an ancient biological mechanism and a vital part of our evolution.

When we feel threatened, such as by the uncertainty surrounding a polygraph exam, the brain tells the sympathetic nervous system to initiate the FoF response. When we experience an environmental trigger, such as the examiner asking a question and we must lie, the FoF instantly activates.

Our blood pressure increases, the hairs on our neck stand up, our pupils widen, our heart rate increases, and we start to sweat. The polygraph instrumentation and software pick up these changes, presenting them to the examiner on their screen.

It’s essentially impossible to defeat or control the FoF because it’s autonomous and doesn’t respond to conscious thought. It’s the same way you can’t control your heart rate or body temperature – your body does that for you.


Countermeasures & Manipulation

Despite the FoF being an autonomous process, there are individuals that attempt to prevent it from fully activating. In 1941, a Chicago Lawyer, Willian Scott Stewart, published an article in Esquire Magazine titled “How to Beat the Lie Detector.”

Stewart introduced a set of “countermeasures” examinees can use to “beat” the polygraph by limiting the FoF response. He stated that by intensifying emotions during the questioning process, examinees could influence the polygraph results.

Examinees would use these countermeasures during the Control Question Test (CQT) exam phase. During this stage of the lie detector test, the examiner creates a baseline response to the examinee’s answers, using this data to compare against the harder questions they ask later in the exam.

Stewart also introduced the concept of “physical” countermeasures for beating the polygraph test. Flexing the leg muscles, curling the toes, or biting the cheek when answering questions seemed to throw off the polygraph, leading to inconclusive results or false positives.

Stewart claimed these countermeasures could reduce polygraph accuracy to less than 50%. However, he introduced these methods in the 1950s before introducing polygraph systems and better examiner training. Today’s polygraph technology and examiner training vastly improved countermeasure detection.

Using these countermeasures is no longer considered a way to beat the polygraph, but that doesn’t stop people from trying. A former Oklahoma City Detective and polygraph examiner, Sergeant Doug Williams, taught people these countermeasures, and the government didn’t appreciate it. In 2015, Williams received a two-year sentence for teaching people countermeasures to beat the polygraph.

Drug-based countermeasures are also becoming increasingly popular as a means to beat the lie detector test. Using drugs like Beat-blockers and anti-anxiety medications, like Xanax, are now the hottest trend in polygraph countermeasures.

The issue is that these countermeasures reduce the FoF response in people that use them during the exam. However, a skilled examiner can pick up when examinees are using these drugs, making them largely ineffective at beating the system.


Research on the Impact of Countermeasures on Polygraph Reliability

The use of countermeasures to beat the polygraph became a growing concern for the government. In 2003, the National Research Council (NRC) conducted a study issued by the Department of Energy on the validity of polygraph testing.

While the NRC focused on polygraph exams for personnel security screening, it studied all evidence on polygraph test validity, with the bulk coming from specific-event investigations. The study’s results surrounded the science underlying the physiological response measurements used in polygraph exams and evidence of polygraph test accuracy in simulated and actual investigations.

The study found that while deceptive psychological states tend to affect their physiological responses measured by the polygraph, other factors, such as the anxiety around being tested, also affect these responses.

To assess polygraph accuracy, the committee sought published and unpublished evidence in studies that provide relevant results. The study concluded that inexperienced examinees without training in countermeasure use can discriminate deception from the truth at rates well above chance but below 100% perfection.


Pathological Liars and How they Affect Polygraph Results

Since the polygraph relies on the FoF response to detect deception, those individuals that don’t feel remorse for their actions or believe they’re telling the truth when lying don’t activate the FoF. As a result, they may pass the polygraph exam, despite being deceptive in their answers. The pathological liar is an example of such a person.

These individuals often believe their own lies, and they don’t experience empathy in the same manner as other people. Therefore, they don’t activate the FoF when lying in a polygraph exam. Pathological liars don’t have the same neural connections between their amygdala and the frontal lobe, meaning they don’t experience guilt or shame about their lying behavior.


Legal Limitations and Admissibility of Evidence

The polygraph is effective at pointing out deceptive behavior during the lie detector test. However, due to the history of the older lie detector machines producing dubious results and wrongful convictions, the US Justice Department doesn’t allow polygraph results as admissible evidence in court.

The history of the inadmissibility of polygraph results as evidence in court started in the 1920s. The attempt to introduce polygraph results as evidence in a murder case in the District of Columbia murder case in the 1920s is notable.

The judge refused to allow the of William Moulton Marston. Marston was the first American to develop lie detector technology, with John Larson and Leonard Keeler refining his work in the 1920s. Marston’s work involved measuring changes in systolic blood pressure during criminal interrogations.

In the 1923 case involving Frye v. United States, the court affirmed the judge’s ruling. They stated the following.

“While courts will go a long way in admitting expert testimony deduced from a well-organized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs. We think the systolic blood pressure deception test has not yet gained such standing.”

As a result, the Frye “general acceptance” exam became a dominant rule in governing the admissibility of expert scientific testimony for the following 70 years, despite the advancement and refinement of polygraph technology, far surpassing Marston’s original method. Today, most courts refuse to admit testimony regarding polygraph evidence, referencing Frye.

Then, in 1993, the Supreme Court established the current guidelines for the admissibility of scientific polygraph evidence in federal court during the “Daubert case.” The Daubert test, found in the “Federal Rules of Evidence” in 2000, requires the court judge to act as the gatekeeper, evaluating whether the basis for admission is technical, proffered scientific, or other specialized knowledge is valid and reliable.

While Daubert replaced Frye, many states, including California, New York, Florida, and Illinois, continue to use Frye. Generally, the court looks at the polygraph result admissibility in several ways. Many courts, especially state courts, maintain the “per se” rule for excluding polygraph exam evidence.


Polygraph Testing, Results, and the Constitution

There are two constitutional issues in the court’s decision regarding the admission of polygraph test results as trial evidence. First, excluding exculpatory polygraph results violates the defendant’s Sixth Amendment right to present evidence.

Second, there’s the claim that admission of inculpatory polygraph results will violate the defendant’s Fifth and Fourteenth Amendment rights involving due process. As a result, courts steered clear of the new evidence of results involved in the progression of polygraph technology, treating polygraph test accuracy as not committing to constitutional dimensions.

For instance, in the 1998 case of United States v. Scheffer, the Supreme Court upheld a military court order stating the “per se” rule excludes polygraph evidence. The court ruled the following.

“Exclusionary rules don’t infringe the rights of the accused to present a defense as long as they are not arbitrary or disproportionate to the purposes they are designed to serve.”” To this day, the scientific community remains extremely polarized about the reliability of polygraph techniques.”

Courts held, however, that the defendant’s Fifth Amendment privilege regarding protection against self-incrimination applies to the polygraph exam process. Thus, the defendant’s refusal to do so cannot be held against them.

Moreover, the courts carefully evaluate all waivers of defendants’ rights to counsel or their right to remain silent regarding stipulation agreements concerning polygraph exams.


Wrapping Up – The Leap in Technology Left Behind

Despite the claims of countermeasures beating polygraphs and the court’s refusal to admit polygraph evidence in most cases, the technology marches on. Polygraph sciences are useful in criminal and employee evaluations, despite the attempts to keep them out of these areas.

Both the courts and the law discount the fact that today’s polygraph machines are a different animal from those invented by Marston, Larson, and Keeler. The refinement in accuracy is highly regarded by industry experts as valid and far beyond the capability of the machines responsible for creating the laws regarding the inadmissibility of polygraph results in court.