What Behavior Does a Polygraph Examiner Look For?

Understanding the Polygraph Instrumentation

The polygraph is an integrated system of sensors, data acquisition hardware, and sophisticated software that work together to capture your body's involuntary physiological responses. A trained polygraph examiner connects several sensor types to the examinee before the test begins [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs.. Each sensor targets a specific physiological system, and together they create a multi-channel picture of your body's autonomic activity throughout the examination. The Federal Psychophysiological Detection of Deception Examiner Handbook published by the U.S. Department of Defense in 2006 standardized the procedures, scoring methods, and quality assurance requirements used across all federal polygraph programs [2]Verified Reliability of the Empirical Scoring System with expert examiners
Confirms Fleiss kappa of.61 indicating substantial inter-rater agreement and 95.4% mean decision agreement excluding inconclusive results..

Modern polygraph systems typically record a minimum of four physiological channels: two respiration channels (thoracic and abdominal), one channel of electrodermal activity, and one channel of relative blood pressure [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs.. Some advanced systems also incorporate plethysmograph sensors for pulse amplitude and motion-detection pads.

Pneumograph — Respiratory Monitoring

The pneumograph consists of two rubber convoluted tubes (also called pneumatic tubes) that wrap around the examinee's body — one around the upper chest and one around the abdominal area [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs.. These tubes expand and contract as you breathe, and the resulting pressure changes are transmitted to transducers that convert them into digital signals.

The polygraph examiner is specifically looking for changes in your breathing pattern. During deception, people commonly exhibit several respiratory anomalies: an increase or decrease in breathing rate, a change in the depth of respiration, suppressed breathing where you hold your breath momentarily, or a shift in the ratio of inhalation to exhalation duration. These changes often occur involuntarily when the sympathetic nervous system activates in response to a threatening stimulus — such as being asked a question you intend to answer deceptively.

Respiratory data is particularly valuable because many people are completely unaware of how their breathing changes under stress. While someone might consciously attempt to control their heart rate or muscle tension, breathing pattern changes are extremely difficult to manipulate without creating obvious artifacts that the examiner will notice immediately.

Cardiosphygmograph — Cardiovascular Monitoring

The cardiosphygmograph uses a standard blood pressure cuff (sphygmomanometer) that the examiner attaches to the examinee's upper arm. In polygraph testing, unlike clinical blood pressure measurement, this cuff is inflated to a lower pressure — typically between 60 and 70 mmHg [3]Verified Relative Accuracy of Polygraph Examiner Diagnosis of Respiration, Blood Pressure, and GSR Recordings
Confirms GSR/electrodermal measures provided the most diagnostic information among individual physiological channels in field polygraph testing. — enough to detect pulse changes and relative blood pressure fluctuations but not enough to cause significant discomfort during the examination.

The cuff records two critical measurements: relative blood pressure changes and heart rate (pulse). When the fight-or-flight response activates, the cardiovascular system responds almost immediately. Blood pressure rises as the heart pumps harder to prepare the body for action, and heart rate increases to deliver more oxygen-rich blood to muscles. The examiner monitors for these spikes in response to specific questions.

Modern cardiograph channels are sensitive enough to detect not just the rate and amplitude of heartbeats but also subtle changes in pulse wave morphology — the shape of each heartbeat's waveform — which can provide additional data about autonomic arousal. Examiners must also be aware that the blood pressure cuff can only be inflated for approximately 10 to 12 minutes before causing the subject discomfort, which is why chart collection periods are kept brief [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs..

Galvanograph — Electrodermal Activity (EDA)

The galvanograph, sometimes called the GSR (Galvanic Skin Response) sensor or EDA sensor, consists of two small electrodes attached to the examinee's fingertips or palm. These sensors measure the electrical conductance of your skin, which changes in direct proportion to sweat gland activity [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs..

The skin conductance response is considered one of the most reliable physiological indicators of sympathetic nervous system arousal. When you experience the stress of deception, your eccrine sweat glands — which are particularly dense on the palms and fingertips — activate, producing a thin film of moisture that increases the skin's ability to conduct electricity. This response typically occurs within 1–3 seconds of the stimulus (the question) and produces a characteristic spike on the examiner's chart.

The NRC's 2003 report confirmed that electrodermal activity is the most sensitive measure in laboratory studies of the detection of deception [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing.. A number of studies have shown that EDA data has a stronger correlation with the external criterion compared to other data recorded during comparison question testing [5]Verified Expertise in Deception Detection Involves Actively Prompting Diagnostic Information Rather Than Passive Behavioral Observation
Confirms expert interviewers using active questioning achieved 97.8% to 100% deception detection accuracy.. The landmark field study by Stanley Slowik and Joseph Buckley (1975) compared the diagnostic value of individual physiological channels and found that electrodermal (GSR) measures provided the most diagnostic information, followed by cardiovascular and respiratory channels [6]Verified The Reliability of Polygraph Examiner Diagnosis of Truth and Deception
Seminal reliability study confirming high inter-rater reliability for experienced examiners using structured scoring methods.. Because the sympathetic nervous system drives EDA exclusively — unlike heart rate, which both branches of the autonomic nervous system influence — it provides a particularly clean signal of sympathetic activation.

From Analog Pens to Digital Analysis

The polygraph has undergone a remarkable technological evolution. Early instruments, used from the 1920s through the 1990s, relied on a kymograph — a mechanical system that drew paper across a writing surface while ink pens traced lines representing each physiological channel. Examiners would manually examine these paper charts, measuring pen excursions with rulers.

Modern polygraph systems have replaced this entirely with digital data acquisition. Today's instruments connect the pneumograph, cardiosphygmograph, and galvanograph sensors to a compact data acquisition module that digitizes the analog signals at high sampling rates — typically 200 samples per second or higher. This control box connects via USB or Bluetooth to the examiner's laptop, where specialized polygraph software displays the data in real time on screen.

The software provides several critical advantages over the old paper-based systems. First, it allows precise digital storage, meaning data can be reviewed, zoomed in on, and compared with surgical accuracy. Second, it enables the use of computerized scoring algorithms that supplement the examiner's manual analysis with objective numerical scores. Third, it facilitates easy sharing of data files between examiners for quality assurance and peer review. Learn more about these workflows in our guide to polygraph examiner digital workflow.

Computerized Scoring Algorithms

Several validated computerized scoring systems are now available that supplement the examiner's manual analysis. The most widely used include PolyScore, developed by the Johns Hopkins University Applied Physics Laboratory (JHU-APL) [7]Verified The Accuracy and Consistency of Polygraph Examiners' Diagnoses
Confirms examiner accuracy of 92.4% for deceptive subjects and 95.5% for truthful subjects in real criminal cases using structured scoring., and the Objective Scoring System version 3 (OSS-3), developed by Raymond Nelson, Donald Krapohl, and Mark Handler [8]Verified A Validation Study of Polygraph Examiner Judgments
Pioneering field validity study finding 92% agreement between polygraph results and independent panel verdicts.. The Computerized Polygraph System (CPS), developed by Scientific Assessment Technologies based on research at the University of Utah, is another established algorithm [7]Verified The Accuracy and Consistency of Polygraph Examiners' Diagnoses
Confirms examiner accuracy of 92.4% for deceptive subjects and 95.5% for truthful subjects in real criminal cases using structured scoring..

PolyScore uses logistic regression analysis based on criminal case data to produce a probability of deception [7]Verified The Accuracy and Consistency of Polygraph Examiners' Diagnoses
Confirms examiner accuracy of 92.4% for deceptive subjects and 95.5% for truthful subjects in real criminal cases using structured scoring.. The OSS-3 is based on measurements of features first described by researchers at the University of Utah — commonly known as "Kircher features" — which include the amplitude of increase for electrodermal and cardiovascular activity along with reduction of respiration activity [8]Verified A Validation Study of Polygraph Examiner Judgments
Pioneering field validity study finding 92% agreement between polygraph results and independent panel verdicts.. Lafayette Instrument Company's LXSoftware is bundled with the OSS-3 scoring algorithm, and also supports PolyScore and other systems [9]Verified Psychophysiological and Behavioral Measures for Detecting Concealed Information: The Role of Memory for Crime Details
Confirms central crime details produce stronger physiological responses than peripheral details in concealed information testing..

These computerized scoring systems have the potential to reduce bias in chart reading and inter-rater variability [7]Verified The Accuracy and Consistency of Polygraph Examiners' Diagnoses
Confirms examiner accuracy of 92.4% for deceptive subjects and 95.5% for truthful subjects in real criminal cases using structured scoring.. A study on the reliability of the Empirical Scoring System with expert examiners found a Fleiss kappa of.61 (95% CI:.54–.68) indicating substantial inter-rater agreement, with mean decision agreement reaching 95.4% excluding inconclusive results [10]Verified The Identification of Concealed Memories Using Event-Related Potentials and Implicit Behavioral Measures
Confirms 90%+ hit rate in detecting concealed thought using P300-based methods.. For a deeper look at how manual scoring works, see our guide to spot analysis in polygraph chart marking and scoring.

Real-Time Monitoring and Recording

During the examination, the polygraph software displays all channels simultaneously as scrolling waveforms on the examiner's screen. The examiner watches these traces in real time while asking questions, noting any significant physiological changes that coincide with specific questions. The software automatically timestamps each question, creating a precise record of which physiological responses occurred in response to which stimuli.

Simultaneously, the entire session is captured on video recording equipment. Many modern polygraph setups use multiple camera angles — one focused on the examinee's face and upper body, and another providing a wider view of the exam room. This video becomes crucial during the post-test review phase, when the examiner compares the physiological chart data with the examinee's observable behavior, body language, and facial expressions.

Sweat Gland Activity — Beyond Basic EDA

While the galvanograph captures overall skin conductance, modern polygraph systems can provide more nuanced data about sweat gland activity. The eccrine sweat glands on your palms and fingertips are under direct sympathetic nervous system control — meaning they respond specifically to emotional and psychological stress, not just temperature regulation [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing..

When you prepare to lie, the brain's limbic system (specifically the amygdala) signals a threat response, and one of the earliest physical manifestations is microscopic activation of these eccrine glands. The examiner watches for both the amplitude (size) and latency (timing) of these sweat responses. A large, rapid-onset electrodermal response occurring 1–3 seconds after a relevant question is flagged as potentially deceptive. The recovery time — how quickly your skin conductance returns to baseline — is also informative. Prolonged elevation suggests sustained autonomic arousal, which often correlates with ongoing deception-related stress.

Motion Sensing — The Activity Pad

The motion-sensing activity pad (also called a countermeasure detection pad) is a thin pressure-sensitive mat placed on the seat of the examinee's chair. It detects physical movements including leg muscle contractions, gluteal clenching, toe pressing, and general body shifting [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs..

The primary purpose of this sensor is to identify physical countermeasure attempts. Some individuals attempt to manipulate their physiological responses by deliberately inflicting subtle pain (such as biting their tongue or pressing a tack hidden in a shoe) or clenching muscles during comparison questions. The goal of such countermeasures is to artificially elevate physiological responses to comparison questions, making them appear similar to responses on relevant questions.

The activity pad renders most physical countermeasures detectable. If the examiner sees motion sensor activation coinciding with comparison questions, it indicates the examinee is attempting manipulation. The OSS-3 algorithm includes a test of proportions to help discriminate between countermeasures and random artifacts [8]Verified A Validation Study of Polygraph Examiner Judgments
Pioneering field validity study finding 92% agreement between polygraph results and independent panel verdicts.. However, published research presents a complex picture: while motion sensors can detect physical countermeasures, some laboratory studies have found that mental countermeasures (such as counting backwards by seven) are more difficult to detect instrumentally [11]Verified The Polygraph and Lie Detection
NRC's comprehensive 2003 review estimating median CQT accuracy at.85 and confirming EDA as the most sensitive polygraph measure..

How the Autonomic Nervous System Drives Polygraph Reactions

To truly understand what a polygraph examiner looks for during a lie detector test, you need to understand the neuroscience behind the fight-or-flight response. The entire foundation of polygraph testing rests on the involuntary activation of the sympathetic nervous system (SNS), a branch of the autonomic nervous system (ANS) that operates outside of conscious control.

The ANS has two opposing branches:

The Sympathetic Nervous System (SNS) — responsible for the fight-or-flight arousal response. It accelerates heart rate, raises blood pressure, dilates bronchial passages, triggers sweat production, and redirects blood flow to muscles. Cardiovascular activity is governed by both the sympathetic and parasympathetic systems, with the former acting through norepinephrine to speed the heart and increase blood pressure [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing..

The Parasympathetic Nervous System (PNS) — responsible for rest-and-digest functions. It slows heart rate, promotes digestion, and returns the body to a calm baseline state through the neurotransmitter acetylcholine [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing..

When you sit in the polygraph chair and the examiner asks a question that you intend to answer deceptively, your brain's threat detection centers — primarily the amygdala — perceive the situation as dangerous. Within milliseconds, a cascade of physiological changes begins: adrenaline surges into the bloodstream, your heart beats faster, blood pressure rises, breathing patterns shift, and your skin begins to produce sweat. This process is autonomous — you cannot consciously prevent it from happening.

What the Examiner Sees on Their Screen

When the fight-or-flight response activates during a relevant question, the examiner observes a characteristic pattern across multiple channels simultaneously:

Respiratory Channel Disruption: The breathing trace shows a sudden change — often a brief suppression or holding of breath, followed by either rapid shallow breathing or a deliberate deep breath as the examinee tries to regain composure.

Cardiovascular Spike: The blood pressure and heart rate traces show a notable increase. The amplitude of the pulse wave grows larger, and heartbeat frequency increases. This spike typically begins within 2–5 seconds of the question and may persist for 15–30 seconds.

Electrodermal Response: The skin conductance trace shows a sharp upward deflection — often the most dramatic of all channels. This reflects sudden eccrine sweat gland activation. The onset is typically 1–3 seconds after the question [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing..

Motion Sensor Baseline: In a straightforward deceptive response without countermeasures, the activity pad should remain relatively quiet. Movement detected during this response alerts the examiner to possible countermeasure techniques.

How the Examiner Differentiates Deception from Nervousness

One of the most common concerns before a polygraph test is: "What if I'm just nervous and the machine thinks I'm lying?" This is a valid concern, and it is one that polygraph methodology has addressed through careful test design.

The key lies in the comparison question technique (CQT), which is the most widely used polygraph methodology [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs.. The examiner does not simply compare your responses to relevant questions against a calm baseline. Instead, they compare your relevant question responses against your responses to carefully crafted comparison (probable lie) questions — questions designed to elicit a mild stress response from truthful examinees.

For example, a comparison question might be: "Before the age of 25, did you ever lie to someone who trusted you?" This question is broad enough that virtually everyone would feel uncomfortable answering "no." A truthful examinee will typically show greater physiological responses to these comparison questions than to the relevant questions. A deceptive examinee, however, will show significantly greater responses to the relevant questions — because those questions pose the real threat of discovery.

This comparison-based approach means that general nervousness — which would affect responses to all questions relatively equally — does not produce the differential pattern that indicates deception. The polygraph is essentially measuring relative reactivity, not absolute arousal levels. Learn more in our guide on diagnostic vs. screening polygraphs and their sensitivity and specificity.

The Role of Fear, Guilt, and Consequence Anxiety

The fight-or-flight response during polygraph testing is driven by several interrelated emotions: fear of detection (the most direct driver — you know you are lying and fear being caught), guilt (your internal moral compass recognizes the act of deception), shame (focused on how being caught would affect your self-image), and consequence anxiety (fear of practical outcomes like job loss or legal trouble).

All of these emotions contribute to autonomic arousal, and the polygraph captures their cumulative physiological effect. The examiner understands that sometimes a question can trigger a strong response for reasons unrelated to the specific issue being tested. In such cases, the examiner typically explores this during the post-test interview and may rephrase the question to remove emotional baggage, allowing the examinee to answer truthfully. A thorough understanding of the pre-test questionnaire process helps examiners identify potential emotional triggers in advance.

Visual and Behavioral Indicators of Deception

While the polygraph instrumentation provides the primary data for determining truth or deception, experienced polygraph examiners also pay close attention to body language, facial expressions, speech patterns, and overall demeanor. These behavioral observations serve as a supplementary data source that can confirm or contextualize the physiological data.

However, it is important to note that research on behavioral cues to deception paints a sobering picture for purely observational approaches. A massive meta-analysis of 116 studies examining behavioral deception cues conducted by Bella DePaulo (2001), published in Psychological Bulletin, found that most behavioral cues are weak or unreliable — explaining why unaided human deception detection hovers near chance levels [12]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
APA's 2011 meta-analysis of 38 studies finding 87% decision accuracy across all validated techniques with 13% inconclusive rate.. This research underscores why instrument-based approaches like polygraph testing are valuable: physiological measurements capture involuntary responses that behavioral observation alone cannot reliably detect.

Research by Timothy Levine and colleagues (2014) found that expert interviewers using flexible, active questioning strategies achieved near-perfect accuracy (97.8% to 100%) in detecting deception — but this expertise involved actively prompting diagnostic information rather than passive behavioral observation [13]Verified Do 'lie detectors' work? What psychological science says about polygraphs
Confirms APA industry meta-analysis found 89% accuracy rate and notes the NRC 2003 identified about 70% lie identification rate.. This finding supports the polygraph examiner's dual approach: combining active, structured questioning with objective physiological measurement.

Micro-Expressions and Facial Cues

Micro-expressions are brief, involuntary facial expressions that typically last between 1/25th and 1/5th of a second [14]Verified Effects of the duration of expressions on the recognition of microexpressions
Confirms the upper limit of microexpression duration is around 1/5 of a second and that recognition can be enhanced with practice.[15]Verified Could Micro-Expressions be Quantified? Electromyography Gives Affirmative Evidence
Provides precise EMG-based ME duration estimates of 307-327ms and confirms MEs are less controllable than macro-expressions.. Pioneered by researchers Haggard and Isaacs in 1966 and formally named by Paul Ekman and Wallace Friesen, these fleeting facial movements reveal emotions a person may be attempting to conceal [14]Verified Effects of the duration of expressions on the recognition of microexpressions
Confirms the upper limit of microexpression duration is around 1/5 of a second and that recognition can be enhanced with practice..

Recent EMG-based research has provided more precise estimates of micro-expression duration, with the main duration ranging from approximately 307 to 327 milliseconds [16]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms the cardio cuff is typically inflated to 60-70 mmHg in polygraph testing.. Research confirms that micro-expressions are less controllable and less consciously recognized compared to regular macro-expressions [16]Verified Cardiovascular and Respiratory Factors Affecting Polygraph Recordings
Confirms the cardio cuff is typically inflated to 60-70 mmHg in polygraph testing.. Seven universal micro-expressions — happiness, sadness, anger, fear, surprise, disgust, and contempt — have been identified across all human cultures by Dr. Paul Ekman's cross-cultural research [15]Verified Could Micro-Expressions be Quantified? Electromyography Gives Affirmative Evidence
Provides precise EMG-based ME duration estimates of 307-327ms and confirms MEs are less controllable than macro-expressions..

While trained examiners look for micro-expressions during the pre-test interview and test phases, these observations are always secondary to the objective physiological data. The PEACE model and cognitive interviewing approach provides structured frameworks for integrating behavioral observation with evidence-based questioning.

Speech Patterns and Verbal Indicators

Beyond physiological data and facial expressions, examiners also note changes in speech patterns. Common verbal indicators include increased response latency (taking longer to answer), changes in vocal pitch or pace, excessive qualifiers or hedging language, unsolicited explanations or over-elaboration, and inconsistencies between pre-test and in-test statements.

These observations are recorded in the examiner's notes and may be referenced during post-test analysis, but they never form the basis for a determination on their own. Polygraph professionals follow strict ethical standards outlined by the APA, which require that conclusions be based on validated physiological scoring methods.

Establishing Baselines and Building Rapport

The pre-test interview is one of the most critical phases of the entire polygraph examination. It typically accounts for a significant portion of the total exam time and serves multiple essential functions.

During the pre-test, the examiner reviews all test questions with the examinee. No question asked during the formal test should come as a surprise — this is a fundamental principle of valid polygraph testing established in the Federal Examiner Handbook [2]Verified Reliability of the Empirical Scoring System with expert examiners
Confirms Fleiss kappa of.61 indicating substantial inter-rater agreement and 95.4% mean decision agreement excluding inconclusive results.. The pre-test also allows the examiner to identify potential medical conditions that could affect physiological readings, such as cardiovascular conditions or medications. For more on how conditions like diabetes may affect testing, see our guide on diabetes and polygraph testing.

The examiner uses this phase to build rapport with the examinee, explain the testing process, review the consent form, and address any concerns. The pre-test interview also includes establishing the examinee's baseline physiology through calibration charts. This baseline information is essential for accurately interpreting responses during the formal test phase.

Acquaintance Test and Stim Test

Most examiners conduct a stimulation (stim) test or acquaintance test before the formal examination. This involves a demonstration — often a card test or number test — in which the examinee is asked to choose an item and then deny their choice while connected to the instrument. The examiner then demonstrates the instrument's ability to detect the known deception.

This phase serves two purposes: it demonstrates to the examinee that the instrument is effective (which research on the bogus pipeline effect suggests increases test validity by enhancing detection apprehension in deceptive examinees), and it allows the examiner to observe how the examinee's physiology responds to a known lie, helping calibrate their interpretation of the formal test charts.

How Examiners Identify Countermeasure Attempts

Countermeasures are deliberate techniques used by examinees to attempt to alter their physiological responses during a polygraph test. They generally fall into two categories: physical countermeasures (such as biting the tongue, pressing toes to the floor, or clenching muscles during comparison questions) and mental countermeasures (such as counting backwards by seven or engaging in arousing mental imagery during comparison questions) [11]Verified The Polygraph and Lie Detection
NRC's comprehensive 2003 review estimating median CQT accuracy at.85 and confirming EDA as the most sensitive polygraph measure..

Modern polygraph examinations use motion-sensing activity pads specifically designed to detect physical countermeasure attempts. When the examiner sees motion sensor activation consistently coinciding with comparison questions, it strongly suggests the examinee is attempting manipulation. The OSS-3 algorithm includes a test of proportions feature that helps distinguish between systematic countermeasure attempts and random artifacts [8]Verified A Validation Study of Polygraph Examiner Judgments
Pioneering field validity study finding 92% agreement between polygraph results and independent panel verdicts..

The research on countermeasures presents nuanced findings. A study by Honts, Raskin, and Kircher found that when examinees used separate EMG analysis, examiners could detect the use of physical countermeasures approximately 80% of the time [17]Verified Appendix F: Computerized Scoring of Polygraph Data (from The Polygraph and Lie Detection)
Confirms PolyScore was developed by Johns Hopkins University APL and describes CPS from the University of Utah.. However, the same research found that without EMG, experienced examiners had difficulty detecting countermeasure use through observation alone [17]Verified Appendix F: Computerized Scoring of Polygraph Data (from The Polygraph and Lie Detection)
Confirms PolyScore was developed by Johns Hopkins University APL and describes CPS from the University of Utah.. This highlights why modern instrumentation — including motion sensors and multiple recording channels — is essential for maintaining test integrity.

Why Countermeasures Are Difficult to Execute Successfully

While countermeasures pose a theoretical threat, successfully executing them in practice is considerably more challenging than internet guides suggest. The examinee must correctly identify which questions are comparison questions and which are relevant questions — a distinction that skilled examiners work to obscure during the pre-test review. The examinee must then apply the countermeasure precisely at the right moment, with enough intensity to create a notable physiological response, but not so much that it creates detectable movement artifacts.

The NRC's 2003 review acknowledged that countermeasures are a concern, noting that specific-incident polygraph tests demonstrate accuracy "in populations untrained in countermeasures" [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing.. The fact that polygraph testing continues to be used extensively by federal agencies including the FBI, CIA, NSA, and DEA speaks to its practical effectiveness as an investigative tool, as outlined in the Federal Examiner Handbook [2]Verified Reliability of the Empirical Scoring System with expert examiners
Confirms Fleiss kappa of.61 indicating substantial inter-rater agreement and 95.4% mean decision agreement excluding inconclusive results.. For those who may be wondering about their options, learn more in our guide on whether you can refuse a lie detector test.

Numerical Scoring Methods

After the formal test charts are collected, the examiner conducts a detailed analysis of the physiological data. Most modern examiners use a numerical scoring system — typically a 3-position or 7-position scale — to assign scores to each physiological channel for each question comparison pair.

The 7-position scale assigns values from -3 (strongly deceptive) to +3 (strongly truthful), with 0 indicating no observable difference between relevant and comparison responses. Scores are assigned independently for respiration, cardiovascular, and electrodermal channels, then summed across all channels and all chart presentations to produce a grand total score. A grand total score of +6 or greater typically indicates non-deception, while -6 or less indicates deception, with scores between these values considered inconclusive [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs..

For a detailed look at how scoring works, including the use of p-values and statistical classifiers, see our guide on p-values in polygraph testing.

Peer Review and Quality Assurance

Professional standards require that polygraph charts undergo peer review before final results are issued. A second qualified examiner independently reviews the chart data, scoring it blind — without knowledge of the original examiner's conclusion. This quality assurance step is designed to reduce individual examiner bias and increase reliability.

Research on inter-rater reliability demonstrates the value of this approach. The seminal reliability study by Frank Horvath and John Reid (1971) found high inter-rater reliability for experienced examiners using structured scoring methods [18]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Describes the OSS-3 algorithm and confirms it exceeded the average decision accuracy of human scorers.. The study by Hunter and Ash (1973) examined real criminal cases with confirmed outcomes and found examiner accuracy of 92.4% for deceptive subjects and 95.5% for truthful subjects when using structured scoring methods [19]Verified Mental and physical countermeasures reduce the accuracy of polygraph tests
Confirms physical and mental countermeasures each enabled approximately 50% of subjects to defeat the polygraph, and that countermeasures were difficult to detect by observation.. The pioneering field validity study by Philip Bersh (1969) found 92% agreement between polygraph results and independent panel verdicts [20]Verified A review of the polygraph: history, methodology and current status
Confirms NRC estimated median CQT accuracy at.85 and that GSR has long been considered the most reliable polygraph measure per Slowik & Buckley 1975..

Accredited Training Programs

Becoming a qualified polygraph examiner requires completion of an APA-accredited training program consisting of a minimum of 400 hours of in-residence instruction [21]Verified Practical Polygraph: FAQ on Electrodermal Activity and the Electrodermal Sensor
Confirms EDA data has a stronger correlation with the external criterion compared to other polygraph channels across multiple studies.. These programs are typically 10 to 17 weeks long and cover a comprehensive curriculum including the history of deception detection, human anatomy and physiology, polygraph instrumentation, test question formulation, chart interpretation, numerical scoring, computerized analysis, pre-test and post-test interviewing, ethics, and legal considerations.

At least 95% of all instruction within an APA-accredited program must be delivered by recognized faculty members. Students must also demonstrate proficiency through practical examinations, completing multiple mock crime examinations under supervision. Explore training options at PEAK CATC, which offers APA-accredited basic training and specialized courses including the 40-hour nonconfrontational interviewing course.

For those interested in the PCSOT specialization for sex offender testing, see our guide on how to become a certified PCSOT polygraph examiner.

Continuing Education Requirements

The APA requires practicing examiners to complete a minimum of 30 continuing education hours every two years in coursework related to polygraphy. A practicing examiner is defined as any member who has conducted polygraph training, quality assurance, or examinations in the previous two years. This ongoing education ensures examiners stay current with evolving techniques, research findings, and standards of practice.

The APA promotes standards for its 2,700+ members through the establishment and publication of standards for professional practice including techniques, instrumentation, analysis, research, training, and continuing education.

What the Research Shows

The accuracy of polygraph testing has been studied extensively, with results varying depending on the methodology used and who is interpreting the data.

The American Polygraph Association conducted a comprehensive meta-analysis published in 2011, reviewing 38 studies that met their qualitative and quantitative requirements. These studies involved 3,723 examinations scored by 295 scorers. The meta-analysis found that the combination of all validated polygraph techniques produced a decision accuracy of 87% (confidence interval 80%–94%) with an inconclusive rate of 13%. Event-specific single-issue testing techniques achieved approximately 89% accuracy, while multiple-issue techniques achieved approximately 85%.

The American Psychological Association noted this industry meta-analysis found an accuracy rate of 89% for polygraph tests, while also noting that the research was conducted by the polygraph industry rather than independent researchers.

The National Research Council's landmark 2003 review, "The Polygraph and Lie Detection," assessed 57 studies and estimated the median accuracy of the CQT at.85 using ROC curve statistics. The NRC concluded that in populations untrained in countermeasures, "specific-incident polygraph tests can discriminate lying from truth telling at rates well above chance, though well below perfection" [4]Verified Cues to Deception: A Meta-Analysis of Behavioral Indicators
Confirms most behavioral deception cues are weak or unreliable, supporting the value of instrument-based approaches like polygraph testing.. The APA itself claims that research studies published since 1980 report average accuracy rates ranging from 80 to 98 percent.

Research on the concealed information test (CIT), as studied by Galit Nahari and Gershon Ben-Shakhar (2010) in the journal Psychophysiology, found that central crime details produced stronger physiological responses than peripheral details, with significant implications for real-world CIT application. P300-based concealed information methods have reported hit rates of 90% and above, as demonstrated by Allen, Iacono, and Danielson (1992).

Understanding Potential Errors

No diagnostic test is perfect, and polygraph testing is no exception. There are two primary types of errors in polygraph testing:

False positives occur when a truthful person is classified as deceptive. The NRC noted that the false-positive error rate of CQT polygraph testing was unknown based on available research. False negatives occur when a deceptive person is classified as truthful.

Several factors can influence accuracy including the examiner's skill and training, the examinee's mental and physical state, the quality of question formulation, and the testing environment. Conditions affecting blood pressure, heart rhythm, or breathing can distort readings, making pre-test screening and correct physiological interpretation essential [3]Verified Relative Accuracy of Polygraph Examiner Diagnosis of Respiration, Blood Pressure, and GSR Recordings
Confirms GSR/electrodermal measures provided the most diagnostic information among individual physiological channels in field polygraph testing.. For special populations, such as elderly examinees, additional considerations apply — see our guide on polygraph exams on elderly examinees.

Knowing Your Legal Protections

Polygraph examinees have important rights that are protected by law and professional ethical standards. In most private-sector employment situations in the United States, the Employee Polygraph Protection Act (EPPA) of 1988 restricts the use of polygraph tests [1]Verified Federal Psychophysiological Detection of Deception Examiner Handbook
Official policy manual standardizing testing procedures, scoring methods, and quality assurance requirements for all federal polygraph programs.. However, exceptions exist for government agencies and certain security-sensitive positions.

You always have the right to decline a polygraph test, though doing so may have different consequences depending on the context. In law enforcement pre-employment scenarios, declining may end the hiring process. In legal proceedings, polygraph results are generally inadmissible in most federal courts, though about half of U.S. states allow polygraph evidence when both parties agree. New Mexico is the only state that allows polygraph evidence without both parties' agreement.

For a comprehensive understanding of your options, read our guide on whether you can refuse a lie detector test. When a polygraph is conducted, you will be asked to sign a consent form detailing your rights, the nature of the examination, and how results may be used.

Learn about how polygraph evidence is treated in specific jurisdictions through our guides on Pennsylvania polygraph admissibility under the Frye standard and Commonwealth v. Shrawder.