Lies on the Line: The Enigma of Polygraph Examinations

In the world of criminal investigations, where uncovering the truth is paramount, the polygraph or lie detector has been a tool of significant interest and debate.  

But have you ever wondered just how the polygraph came to be? Do they really work? Have they ever successfully been used to solve crimes? 

These answers and more we explore below.

The History and Application of the Polygraph

Invented in 1921 by John Augustus Larson, a police officer in Berkeley, California, the polygraph machine marked a significant leap in criminal investigations. Larson believed this device could detect dishonesty by measuring physiological changes, such as blood pressure, pulse, respiration, and skin conductivity. The theory posited that deceptive answers would yield distinct physiological responses, differentiating them from truthful answers.

The polygraph’s first brush with the legal system occurred in 1923 when William Moulton Marston attempted to introduce polygraph test results as evidence in the case United States v. Frye. The court staunchly rejected this, marking the inception of the Frye Standard, a benchmark for the admissibility of scientific evidence in courtrooms. This principle stressed that for scientific evidence to be considered, the method used must have widespread acceptance in its specific field. Despite the advancements and refinements in polygraph technology over the years, the echoes of the Frye Standard continue to influence the polygraph’s contentious standing in legal contexts today. 


How Does a Polygraph Work? 

In essence, the polygraph doesn’t directly detect lies. Instead, it measures physiological responses that may accompany truth-telling or deception. It operates on the premise that emotional reactions can involuntarily manifest in these measurable physiological changes. Let’s delve into the technical workings and the process that makes up a polygraph examination.

Technical Mechanics of the Polygraph

  • Cardiographs: These measure heart rate. A set of pneumograph tubes is wrapped around the examinee’s chest to monitor the heart’s beats per minute.
  • Galvanometers: Used to gauge skin conductivity. Small electrodes are attached to the examinee’s fingers or palms, which assess the skin’s ability to conduct electricity. When an individual is stressed or anxious, sweat production can increase, leading to a change in skin conductivity.
  • Pneumographs: These measure breathing rate and depth by monitoring the examinee’s inhalation and exhalation patterns.

The Polygraph Process

  • Pre-test interview: Before the actual test, the examiner discusses the test procedure and reviews the questions that will be asked. This helps to familiarize the examinee with the process, potentially easing any anxieties.
  • Question formulation: Polygraph tests use a mixture of relevant questions (about the specific incident under investigation), comparison/control questions, and neutral questions. The examiner observes the physiological responses to different types of questions to infer deception or truthfulness.
  • Testing phase: While being asked a series of questions, the examinee’s physiological responses are simultaneously recorded. Their reactions to specific questions are then compared to baseline measurements and control questions.

Preparation and Execution

  • Environment: The testing environment is controlled to minimize distractions, ensuring accuracy in readings.
  • Equipment Calibration: Before starting, the equipment is calibrated to the individual’s physiological responses.
  • Interrogative Technique: The examiner adopts a structured and consistent interrogative technique. Randomizing the order of questions can prevent the examinee from anticipating and controlling their responses.
  • Post-test Analysis: Once the test concludes, the examiner analyzes the data, comparing responses to control and relevant questions, ultimately drawing conclusions about the examinee’s truthfulness on the topic under investigation.

One important aspect to note is the interpretation of the results is subjective, relying heavily on the skill and experience of the polygraph examiner.


Controversies and Criticisms

A significant debate centers on the accuracy and reliability of lie detector tests. Critics argue that polygraph tests rest on the unverified assumption that deception is accompanied by anxiety, which in turn produces noticeable physiological changes. Yet, individuals may exhibit these physiological responses for a plethora of reasons unrelated to deceit, leading to potential false positives.

Questioning Reliability and Validity

    • The scientific community remains divided on the polygraph’s efficacy. Research and studies spotlight inconsistencies in test results. Various factors, including the examiner’s competence and the subject’s mental and physical condition, can influence outcomes. The American Psychological Association has highlighted these concerns, underscoring the limited reliability and validity of polygraph testing.

Notable Errors

    • Instances where polygraph tests have been proven wrong cast further doubt on their utility. Innocent individuals have sometimes been wrongly accused based on polygraph results, while actual perpetrators might pass the test, a phenomenon known as “beating the polygraph.”
    • A notable case is that of Gary Ridgway, the Green River Killer, who passed a polygraph test in 1984, allowing him to evade justice for nearly two more decades. Conversely, innocent individuals have faced unjust scrutiny and accusations based on inaccurate polygraph results.

Legal and Ethical Concerns

    • Legal systems worldwide exhibit varying stances on polygraph test admissibility as evidence. The admissibility of polygraph evidence in criminal trials remains a contentious issue. While some jurisdictions in the U.S. may permit polygraph evidence under certain conditions, the general rule skews toward exclusion, reinforcing the cautious and critical stance of the legal community towards polygraph testing in the context of criminal law. The potential for inaccurate results, leading to miscarriages of justice, underscores the legal hesitations and restrictions applied to polygraph testing within the criminal law framework.
    • Over a quarter of the known 311 people exonerated through post-conviction DNA testing had given false confessions. The Reid Technique, a widely used interrogation method based on polygraph testing discussed in an article in The New Yorker,  has been linked to producing false confessions. As there is no national database on wrongful convictions, the true extent of the issue remains unknown. However, the data suggests that false confessions are not uncommon, and interrogations incorporating polygraph tests like the Reid Technique can potentially contribute to such outcomes.

In light of these controversies and criticisms, while the polygraph remains a tool in investigative and security contexts, its use is tinged with caution and skepticism, underscoring the critical need for complementary investigative approaches and methods.

Notable Cases of Polygraph Use 

Ryan Brunn: Child Predator Fails Polygraph After Claiming Innocence

A polygraph test played a significant role in unmasking child murderer Ryan Brunn In Georgia in 2010. After the mutilated body of little Jorelys Rivera was discovered in a trash compactor, the prime suspect Brunn was subjected to a polygraph examination by Keith Sitton, a special agent with the Georgia Bureau of Investigation. Despite Brunn’s initial confidence and assurance on his innocence, the outcome of the polygraph test didn’t align with his claims. With each denial of involvement that Brunn made, the test pointed contrary, and unsealed the fact that he was lying.

The accuracy of the polygraph test outcome ultimately transformed the investigation’s course. The “deception” identified during the test forced Brunn into the spotlight as a prime suspect, resulting in his arrest the following day. Eventually, this led to Brunn confessing his despicable act in a Cherokee County courthouse, providing graphic descriptions of how he manipulated, abused, and took the life of Jorelys Rivera. After his sentencing, he took his own life in prison. Hence, the pivotal point connecting these turn of events was indeed the polygraph examination, affirming its indispensable value in probing criminal investigations. You can watch a video that contains clips of his polygraph here

Weleetka Murders

The 2008 killings of Taylor Paschal-Placker and Skyla Whitaker in Weleetka, Oklahoma, remained a mystery for years. Two young girls were found shot dead along a rural road, leading to a statewide manhunt for their killer. In the ensuing investigation, several individuals were given polygraph tests, including persons of interest. Kevin Sweat, initially arrested for another crime, became a suspect in this case. During the investigation, Sweat was subjected to a polygraph test. While specific details about his polygraph results remain less publicized, the combination of evidence led to his confession and eventual conviction for the murders of both girls.

Aldrich Ames Case

Aldrich Ames, a CIA officer turned Russian spy, caused substantial damage to U.S. intelligence operations in the 1980s and early 1990s. Ames was responsible for the compromise of several U.S. assets, many of whom were executed. Surprisingly, even after his espionage activities began, Ames passed two polygraph examinations in 1986 and 1991, raising significant concerns about the reliability of polygraph tests. His case remains one of the most notable instances where the polygraph failed to detect a high-stakes deception, leading to intensified scrutiny and debate over the machine’s efficacy in security and counterintelligence operations. Ames himself has even given a statement on his concerns of the United State’s overeliance on polygraphs. 

Final Thoughts

The use of polygraphs in criminal investigations has always been a topic of debate, particularly concerning their accuracy and potential implications with false confessions. Meanwhile, lie detection systems are undergoing significant transformations, leveraging cutting-edge technology for more precise results. 

Nonetheless, as we move forward, it’s important to remember that even advanced lie detection systems may continue to provoke the same debates about accuracy, ethical use, and the potential for misuse that surround traditional polygraphs.



Can you cheat on a lie detector test?

While polygraph (lie detector) tests are designed to detect any deceptive behavior, there have been cases where individuals have attempted to cheat the test using a variety of strategies. These may include physical or mental techniques to control physiological responses. However, it is important to note that examiners are trained to recognize such deceptive behaviors, and attempting to cheat a lie detector test can raise suspicion and lead to a negative outcome.

What questions do they ask on a polygraph?

The questions asked during a polygraph test will vary based on the specific context and purpose of the examination. Generally, they can be categorized into three types:

  1. Relevant Questions: These relate directly to the matter at hand and address specific concerns the examination is intended to clarify.
  2. Control (Comparison) Questions: These establish a baseline for physiological responses, often by asking about past behaviors or morally ambiguous actions.
  3. Irrelevant Questions: These serve as neutral questions unrelated to the investigation and help to create a baseline for the person’s normal physiological responses.

How do you stay calm during a lie detector test?

Should you ever find yourself in a situation where you must take a polygraph test, considerr the following tips:

  1. Get a good night’s rest before the examination to ensure you feel well-rested and less anxious.
  2. Avoid stimulants, such as caffeine, that may heighten your nervousness and affect your body’s responses during the test.
  3. Practice deep breathing and other relaxation techniques to stay centered and calm.
  4. Listen carefully to each question and answer honestly, focusing your thoughts only on the question at hand without letting your mind wander.
  5. Be open about any concerns or anxieties you have regarding the examination with the polygraph examiner, who may offer reassurances or additional guidance.
Lou Nightingale
Author: Lou Nightingale

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