Behavioral Cues Analyzed by a Polygraph Examiner in Lie Detector Tests


Polygraph examinations, commonly known as lie detector tests, play a crucial role in identifying deception. These tests rely on the expertise of polygraph examiners who analyze various behavioral indicators to determine the truthfulness of individuals. In this blog, we will explore the behavior that polygraph examiners look for during a lie detector test and understand the significance of their observations.

Understanding the Polygraph Test

To comprehend the behavior analyzed in a polygraph examination, it is important to grasp how the test functions. The polygraph machine, equipped with sensors, records physiological responses such as blood pressure, heart rate, respiration patterns, and electrodermal activity. These measurements are then used to assess the subject’s truthfulness. Additionally, the examiner poses different types of questions, including relevant, irrelevant, and control questions, to elicit distinct reactions.

Behavioral Indicators of Deception

Physical signs observed during the test

During a polygraph examination, the polygraph examiner carefully monitors physical signs that may indicate deception. Changes in blood pressure and heart rate can reveal heightened stress or anxiety. Fluctuations in respiration patterns, such as rapid breathing or shallow breaths, may indicate nervousness. Electrodermal activity, measured through sweat response, can provide insights into emotional arousal and physiological reactions.

Non-verbal cues examined by the polygraph examiner

Non-verbal cues offer valuable information about a subject’s truthfulness. Polygraph examiners pay close attention to microexpressions, which are fleeting facial expressions that may contradict the subject’s verbal responses. Body language and posture can also reveal signs of discomfort or attempts to conceal information. Eye movements, including prolonged blinking or avoiding eye contact, might suggest uneasiness or attempts to fabricate.

Psychological and cognitive factors considered by the examiner

In addition to physical and non-verbal cues, polygraph examiners assess various psychological and cognitive factors. Changes in speech patterns and vocal tone, such as voice trembling or unusual hesitations, can raise suspicions of deception. Verbal indicators of deception, such as inconsistency in responses or contradictory statements, provide further insight into the subject’s truthfulness. Psychological stress indicators, like excessive sweating or visible nervousness, are also taken into account during the examination process.

Polygraph Test Techniques and Methodologies

Comparison Question Technique (CQT)

The Comparison Question Technique, or CQT, is one of the most commonly used polygraph test techniques. It involves asking the subject a series of relevant questions pertaining to the specific incident being investigated, along with control questions that are designed to elicit a known physiological response. The subject’s physiological responses to the relevant and control questions are compared to determine any significant deviations, which may indicate deception.

Concealed Information Test (CIT)

The Concealed Information Test, or CIT, focuses on the subject’s recognition of specific details related to a crime or event under investigation. The test includes multiple-choice questions, with one correct answer and several foils. The subject’s physiological responses to each option are measured, and if a stronger response is observed to the correct option, it suggests knowledge of the concealed information. The CIT is based on the assumption that a guilty individual will exhibit a stronger physiological response to the relevant information.

Relevant/Irrelevant Test (RIT)

The Relevant/Irrelevant Test, or RIT, is a polygraph test methodology that involves asking both relevant and irrelevant questions to assess the subject’s truthfulness. Relevant questions pertain to the specific incident being investigated, while irrelevant questions are unrelated. The examiner compares the subject’s physiological responses to the relevant and irrelevant questions, looking for significant differences. Deceptive individuals are expected to show greater physiological arousal in response to the relevant questions.

Guilty Knowledge Test (GKT)

The Guilty Knowledge Test, or GKT, is primarily used in investigations where the examiner has specific knowledge of details only known to the perpetrator and investigators. The test consists of multiple-choice questions, with one option containing the guilty knowledge and the others serving as foils. The subject’s physiological responses are measured, and a stronger response to the option with the guilty knowledge suggests familiarity with the information, indicating possible guilt.

Interpretation of Polygraph Results

The role of the polygraph examiner is pivotal in the interpretation of test results. They meticulously analyze the collected data, distinguishing between truthful and deceptive responses. This analysis requires considering contextual factors and establishing a baseline for the subject’s behavior. By combining physiological, non-verbal, and psychological indicators, the examiner forms an assessment of the subject’s truthfulness.

Limitations and Controversies

Despite their widespread use, polygraph examinations face criticism and limitations. False positives and false negatives can occur, leading to incorrect conclusions. The tests are also susceptible to manipulation and countermeasures, which individuals can employ to deceive the examination. Moreover, the admissibility of polygraph results in court varies, and legal guidelines and regulations govern their use.

Applications of Polygraph Examinations

Law enforcement investigations

Polygraph examinations have widespread application in law enforcement investigations. They are utilized to gather information, assess the credibility of suspects, and aid in the identification of perpetrators. By analyzing behavioral cues and physiological responses, polygraph examiners assist law enforcement agencies in narrowing down suspects, verifying alibis, and uncovering crucial details that can aid in solving crimes.

Pre-employment screenings

Many organizations utilize polygraph examinations as part of their pre-employment screening process, especially for positions that require high levels of trust and security. Polygraph tests help assess the honesty and integrity of job applicants, particularly in fields such as law enforcement, government agencies, and sensitive industries. These screenings can assist employers in making informed decisions during the hiring process.

Criminal justice system

Polygraph examinations find application within the criminal justice system, where they can be used to assist in the investigation and monitoring of individuals on parole or probation. Polygraph testing can be employed to verify compliance with conditions, assess the risk of reoffending, and gather additional information related to criminal activities. However, the admissibility and use of polygraph results as evidence vary across jurisdictions.

National security and intelligence agencies

National security and intelligence agencies employ polygraph examinations as a tool to assess the trustworthiness and reliability of individuals involved in sensitive positions. This includes personnel working in defense, intelligence, and counterintelligence sectors. Polygraph tests help identify potential security risks, protect classified information, and mitigate the chances of espionage or unauthorized disclosure.

Private sector and corporate use

Polygraph examinations are also utilized in the private sector and corporate settings for various purposes. Companies may employ polygraph testing to investigate instances of theft, fraud, or other misconduct within their organizations. Additionally, in cases involving workplace accidents or incidents, polygraph tests can aid in determining liability and uncovering the truth. However, it is important to note that the use of polygraph examinations in the private sector may be subject to legal and regulatory considerations.


Polygraph examinations are a valuable tool in detecting deception, with polygraph examiners playing a crucial role in analyzing behavioral cues. By observing physical, non-verbal, and psychological indicators, these experts aim to differentiate between truthfulness and deception. However, it is essential to acknowledge the limitations and controversies surrounding polygraph tests, including potential inaccuracies and legal considerations. Understanding the behavior analyzed in polygraph examinations helps shed light on their significance while encouraging a critical approach to their interpretation.