How Accurate Are Polygraph Tests?

With continued advancements in technology and the study of human physiology, it’s unlikely that we’ll see polygraph examination made obsolete any time soon. 

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Often referred to as “lie detectors,” polygraph tests have long held a curious place in both pop culture and criminal justice. These tests are often portrayed as definitive truth-seeking tools, capable of catching a suspect in a lie with the flicker of a needle.

But outside of tabloids and TV dramas, the reality of polygraph testing is far more complicated. Every detail matters, from the testing equipment to the training of the examiner and the testing location.

So, just how accurate are polygraph tests, and when should we trust them? 

How Polygraph Tests Work

A physiological recorder is commonly used as the primary tool for polygraph testing. 

This recorder is an instrument used to gauge autonomic arousal by measuring heart rate/blood pressure, skin conductivity, and respiration. 

Lie detectors don’t directly detect lies. Instead, they measure specific stress responses believed to correlate with deception.

Polygraph testing typically includes something called a “pretest phase,” which is used to explain the test to the subject and review each question. This phase is specifically meant to confirm that the subject understands the questions, as well as prompt any concerns regarding deception. 

Polygraph Questioning Techniques

Polygraph testing includes a few different techniques. 

The Control Question Test (CQT) is a testing format widely used in criminal investigations, aiming to analyze and compare questions deemed relevant to the subject. These questions are often broad in scope. 

There are also Guilty Knowledge Tests, commonly referred to as GKTs, which involve building out multiple-choice tests pertaining to knowledge that only a guilty subject could possess.

GKTs are used less often and have limitations. For example, investigators require knowledge of the same information possessed by a guilty party, which isn’t always practical. 

Finally, there is the Directed Lie Test (DLT), which consists of control questions and comparison, while the Relevant/Irrelevant Technique (R/I) focuses on contrasting relevant/irrelevant questions. 

Debating the Accuracy of Polygraph Tests

Most controversy surrounding polygraph tests centers around their accuracy and legitimacy. 

According to the methods and training of a polygraph examiner, the results of studies vary dramatically; mostly because obtained accuracy from one application won’t always carry over to the next. Also, the standardization of this type of testing is challenging to implement uniformly. 

There are certainly obstacles and variables that could potentially interfere with the accuracy of a polygraph, but there are also several points of universal agreement amongst researchers: 

• While imperfect, polygraphs are significantly better than chance
• To date, there is no better means of deception detection and efficacy 
• Specific issue tests trump all others regarding accuracy
• The examiner’s specific skill set and experience are vital to the result 

Practical Applications for Polygraph Examinations

While the media often presents polygraph tests as a high-stakes event in legal proceedings or a playful way to get your favorite YouTube personality to spill the beans, lie detector tests can play a major role in solving conflicts in relationships of all kinds. 

Accusations of theft, sexual misconduct, substance abuse, and more can be at the center of a polygraph examination. Using this lie detection method can aid in trust-building, settle disputes, and bring clarity to situations like infidelity. 

A trained and licensed polygraph examiner can perform a test in a neutral location and provide an unbiased assessment of the results. With the proper equipment and adherence to industry standards, accuracy as high as 98% is possible.

The Legal Admissibility of Polygraph Tests

It’s a common misconception that polygraph examination results are not admissible as evidence in court. While some jurisdictions exclude polygraphs as admissible evidence, citing concerns regarding reliability and potential prejudice, the rules differ between states.  

For example, private polygraphs may be used in defense strategies despite their highly contested evidentiary value. In some cases, states allow results if both parties stipulate in advance.

While polygraphs aren’t universally accepted in the legal system, they do have their place.

Usage of Polygraphs in Law Enforcement and Hiring

In addition to law enforcement investigations, hiring for high-trust roles in industries like security and government often involves polygraph testing, not necessarily as a pass/fail assessment, but rather as a tool for vetting. This method can help verify statements, uncover inconsistencies, and offer an additional layer of insight that interviews and background checks just don’t cover. 

A polygraph test is a tool; it’s not meant to be a replacement for other parts of the evaluation process. In that context, an accuracy rate above 90% makes these supplemental exams especially valuable. Despite the generally agreed-upon concept that polygraphs can be misused and abused, they’ve still proven helpful in criminal investigations and have successfully helped resolve crimes in situations where other methodologies failed. 

Scientific Consensus and Further Research

In light of continued, widespread usage of polygraph testing, the scientific consensus regarding their overall accuracy remains largely unsettled. The variables that surround each test and each application just make a universal determination of accuracy impossible. 

The American Polygraph Association, a professional organization for examiners, asserts that polygraphs can maintain accuracy levels over 90% provided the testing is conducted by trained professionals. The Polygraph Association maintains that many criticisms result from poorly administered tests or a general misunderstanding/misapplication of polygraph data. 

Agencies like the Department of Defense continue leaning on polygraphs as part of their internal vetting process, citing overall effectiveness as investigative tools rather than lie detectors.

The Verdict on Polygraphs

It is hard to deny that there is a place for polygraphs, or that they are valuable in certain settings.

Widespread use of polygraph tests continues today in government agencies, law enforcement, and employers as a means of gathering information, and for individuals and families as a means of conflict resolution and closure. 

With continued advancements in technology and the study of human physiology, it’s unlikely that we’ll see polygraph examination made obsolete any time soon.