Concealed Information Test (CIT): Complete Examiner Guide

Definition and Core Concept

The Concealed Information Test (CIT) is a psychophysiological examination technique designed to determine whether an individual possesses specific knowledge related to a crime or investigated event. Unlike traditional polygraph approaches that attempt to detect deception directly, the CIT tests for recognition of information that only a guilty party or knowledgeable witness could possess.

Originally developed by psychologist David T. Lykken in 1959 and initially termed the "Guilty Knowledge Test" (GKT), the technique was later renamed the Concealed Information Test to more accurately reflect its mechanism [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. Lykken's landmark 1959 paper in the Journal of Applied Psychology demonstrated that 89.8% of participants could be correctly classified using the GSR-based guilty knowledge test [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. The name change acknowledged that the test does not measure "guilt" in a moral or legal sense, but rather detects whether specific information is concealed within the examinee's memory. Today, both terms appear in the literature, though CIT is preferred among researchers.

How the CIT Works in Practice

The CIT operates on a multiple-choice recognition paradigm. The examiner presents the examinee with a series of questions, each containing one critical item (a detail of the crime known only to investigators and the perpetrator) embedded among several plausible but incorrect alternatives.

For example, if a robbery suspect is being tested and investigators know the stolen item was a gold watch, the examiner might ask: "Regarding the item stolen from the victim, was it: a diamond ring, a gold watch, a silver bracelet, a leather wallet, or a pearl necklace?"

An innocent person — who genuinely does not know what was stolen — will show roughly equal physiological responses to all five items, since none carries special significance. However, a guilty person who recognizes "gold watch" as the correct answer will produce an involuntary orienting response to that item, even while trying to appear equally reactive to all alternatives [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies.

The power of this method lies in its logical structure. If an examinee consistently shows enhanced physiological reactions specifically to the critical items across multiple questions, the probability that this pattern occurred by chance can be calculated precisely. With five alternatives per question and five separate questions, the probability of a random innocent pattern mimicking a guilty pattern is astronomically low (1/5 raised to the 5th power = 1 in 3,125). Understanding how various types of polygraph examinations differ is essential for examiners choosing the right method for each case.

Historical Development

While Lykken formalized the CIT framework in his landmark 1959 paper and 1960 empirical study [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants, the conceptual roots trace further back. Early polygraph practitioners recognized that suspects sometimes reacted to crime-specific details, and the Peak of Tension (POT) test — a predecessor technique — operated on similar principles. However, Lykken provided the first systematic theoretical framework connecting the test to established psychological mechanisms, specifically the orienting response described by Sokolov in 1963.

In the decades following Lykken's work, the CIT was primarily studied in laboratory settings in North America and Europe. Meanwhile, Japanese police adopted the technique for operational use beginning in the 1950s [5]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test in Forensic Investigations
Confirms GKT extensively used in Japan since the 1950s, with field application data from Japanese police [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues. The Keeler model 302 polygraph was first introduced to Japan in 1953, and since that year police officers and technical officers have been trained as polygraph examiners at the National Institute of Police Science [14]Verified Development of the Polygraph Technique in Japan for Detection of Deception
Confirms over 5,000 polygraph examinations per year in Japan with ~90% accuracy rate, and court acceptance of results. This parallel development — laboratory research in the West and field application in Japan — has shaped the technique's current status in forensic psychophysiology. For a deeper dive into this history, see our guide on the history of polygraph use in Japan.

The Orienting Response Explained

The theoretical backbone of the CIT is the orienting response (OR), a well-established psychological phenomenon first systematically described by Russian physiologist Evgeny Sokolov. The orienting response is the body's involuntary reaction to a stimulus that is novel, significant, or personally meaningful [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies. When we encounter something that stands out from background stimuli, our nervous system produces a characteristic pattern of physiological changes.

These changes include increased skin conductance (due to sweat gland activation), heart rate deceleration (a parasympathetic response associated with attentional processing), decreased respiration rate and amplitude, and specific brain electrical patterns (the P300 event-related potential) [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies [7]Verified Field Findings From the Concealed Information Test in Japan
Confirms detailed field CIT data from Japan including searching CIT methodology and question-focused judgment. The critical insight for CIT application is that these responses are largely involuntary. Even when a person is highly motivated to conceal their recognition, the orienting response fires automatically as part of the brain's stimulus evaluation system.

Why the Orienting Response Is Ideal for Detection

Several properties of the orienting response make it particularly well-suited for concealed information detection. First, it is automatic — it does not require conscious effort and is difficult to suppress completely. Second, it is stimulus-specific — it occurs in response to meaningful stimuli while habituating rapidly to repeated neutral stimuli. Third, it is measurable across multiple physiological channels, providing convergent evidence [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. Fourth, it is well-understood theoretically — decades of basic research in cognitive psychophysiology have mapped its mechanisms in detail [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies.

This strong theoretical grounding distinguishes the CIT from most other polygraph techniques. The Zone Comparison Test (ZCT), for example, relies on comparison question methodology, which lacks a comparably clear theoretical mechanism. The CIT's connection to established cognitive science gives it unique standing among psychophysiological detection methods.

Memory and Recognition Processes

The CIT depends on memory encoding and retrieval. For the test to work, the guilty examinee must have: (1) perceived the crime-relevant detail during the event, (2) encoded it into memory, and (3) retained it until the time of testing. Research by Nahari and Ben-Shakhar (2010) found that central crime details produced stronger physiological responses than peripheral details, with direct implications for real-world CIT application [4]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 the CIT.

Items chosen for CIT questions should involve central, salient features of the crime that a perpetrator would almost certainly have noticed and remembered. The color of a victim's clothing, the type of weapon used, the specific location where a body was left — these are strong CIT candidates. Understanding how memory affects polygraph testing is essential for examiners selecting effective CIT items. Additionally, Waid and Orne (1980) found that electrodermally labile subjects were more frequently detected in CIT tasks, highlighting the impact of individual physiological differences on test performance [10]Verified Electrodermal Lability and Concealed Information Detection
Confirms individual differences in physiological reactivity (electrodermal lability) affect CIT detection accuracy.

Fundamental Distinctions

Understanding the distinction between the CIT and the Comparison Question Test (CQT) is essential for examiners. The CIT detects recognition of information — it measures whether the examinee recognizes crime-specific details among neutral alternatives, based on the well-established orienting response mechanism [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies. The CQT detects deception through comparison — it compares physiological responses to relevant questions against comparison questions, based on the assumption that guilty people react more strongly to relevant questions while innocent people react more to comparison questions.

The CIT draws on decades of basic research in orienting response theory, attention, and memory — established fields within cognitive neuroscience [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues. The CQT, by contrast, has been criticized for lacking a clear theoretical mechanism. A survey of members of the American Psychological Association and the Society for Psychophysiological Research found that 77% of SPR and 72% of APA Division 1 members believed the CIT to be based on scientific principles, compared to only 36% and 30% for the CQT respectively [5]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test in Forensic Investigations
Confirms GKT extensively used in Japan since the 1950s, with field application data from Japanese police. For a comprehensive list of validated approaches, see our APA validated polygraph techniques guide.

Applicability and Practical Trade-offs

Despite its stronger scientific foundation, the CIT is far less widely used than the CQT in practice. The primary reason is applicability: the CIT requires the examiner to possess specific crime details that are unknown to the public and that the guilty person would remember [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies. Many investigations simply do not produce enough suitable items. Research by Podlesny (2003) found usable CIT items in only 7% of 758 FBI case files examined [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues.

The CQT can be applied to virtually any situation where a yes/no question about behavior can be formulated. Additionally, the CIT is designed for specific-issue investigations rather than screening. Pre-employment polygraph testing, which constitutes a large portion of the polygraph industry, typically requires screening-type protocols where the CIT is not applicable.

Error Profile Differences

The CIT and CQT produce very different patterns of errors. The CIT's hallmark is an extremely low false-positive rate — approximately 5% across studies — meaning innocent people are very rarely identified as possessing guilty knowledge [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies. However, its false-negative rate is higher, meaning some guilty people may escape detection when few CIT items are available or when the person has poor memory for crime details.

The CQT tends to have the opposite pattern: higher sensitivity (catching more guilty people) but also a higher false-positive rate (incorrectly classifying more innocent people). For examiners or attorneys weighing which technique to recommend, this error trade-off is critical. In contexts where protecting innocent suspects is paramount, the CIT offers a significant advantage. Learn more about error patterns in our guide to inconclusive and false polygraph results.

Electrodermal Activity (Skin Conductance)

Skin conductance response (SCR) is considered the most reliable single autonomic measure for CIT detection [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies. Measured via electrodes placed on the fingertips or palms, SCR reflects eccrine sweat gland activity controlled by the sympathetic nervous system. When an examinee recognizes a critical item, the orienting response triggers a measurable increase in skin conductance within 1–5 seconds of stimulus presentation.

The Meijer et al. (2014) meta-analysis found a mean effect size (d*) of 1.55 for SCR across CIT studies [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. The earlier Ben-Shakhar and Elaad (2003) meta-analysis, covering 80 laboratory studies with 5,198 participants, reported the same overall average effect size of 1.55 for SCR, with mock-crime studies producing an even higher average of 2.09 [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. Under optimal conditions — motivational instructions, deceptive verbal response, and at least five questions — the effect size reached 3.12 [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants.

Cardiovascular Measures

Heart rate and blood pressure provide valuable supplementary information in the CIT. The characteristic cardiovascular response to a recognized item is heart rate deceleration — a brief slowing of the heart following presentation of a significant stimulus [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. This deceleration reflects parasympathetic (vagal) activation associated with attentional orienting and is the opposite of what might be expected from a simple "stress" model. The Meijer et al. (2014) meta-analysis found a mean effect size of 0.89 for heart rate changes [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies.

Finger pulse amplitude typically decreases in response to recognized items, reflecting peripheral vasoconstriction. While individually less diagnostic than SCR, cardiovascular measures contribute meaningfully when combined with other channels. Examiners should be aware that medications can affect polygraph test results, including cardiovascular measures.

Respiration

Respiration patterns change in characteristic ways during CIT recognition. Examinees tend to show suppression of respiration amplitude and rate following presentation of a recognized item. This respiratory suppression — shallower, slower breathing — reflects the attentional capture component of the orienting response [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies.

The Meijer et al. (2014) meta-analysis found a mean effect size of 1.11 for respiration line length (RLL) [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. Respiration is measured using pneumograph tubes placed around the chest and abdomen. These sensors detect changes in the circumference of the thoracic and abdominal regions during breathing. Respiration measures add incremental validity to CIT scoring, particularly when SCR responses are ambiguous. Understanding purposeful distortion in polygraph charts helps examiners distinguish genuine respiratory patterns from deliberate manipulation.

Brain Event-Related Potentials (P300)

Electroencephalographic (EEG) measurement of event-related potentials (ERPs), particularly the P300 component, represents a newer approach to CIT measurement. The P300 is a positive-going brain wave occurring approximately 300–800 milliseconds after stimulus presentation, and it is larger for stimuli that are meaningful, rare, or task-relevant [7]Verified Field Findings From the Concealed Information Test in Japan
Confirms detailed field CIT data from Japan including searching CIT methodology and question-focused judgment.

The Meijer et al. (2014) meta-analysis found the largest mean effect size (d* = 1.89) for P300, though P300 outperformed SCR only in the personal-item paradigm, not in the mock-crime paradigm [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. A 2025 meta-analysis by Knappe, Ullsperger, and Kirschner included 54 experimental studies and found a large mean effect size (d*) of 1.59 for P300, with Complex Trial Protocols maximizing effect sizes [8]Verified Decoding Deception with the P300: A Meta-Analysis of the Concealed Information Test
Confirms large mean effect size (d*=1.59) for P300 across 54 studies, with Complex Trial Protocols maximizing effect sizes.

The most validated P300-based CIT protocol is the Complex Trial Protocol (CTP), developed by J. Peter Rosenfeld and colleagues at Northwestern University in 2008 [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy. The CTP was specifically designed to resist countermeasures that defeated earlier P300 methods, achieving high accuracy even with countermeasure-trained subjects [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy. Diagnostic accuracy from CTP studies has ranged from 75–90%, with enhancements using N200, performance feedback, and auxiliary tests restoring accuracy above 90% [11]Verified Review of Recent Studies and Issues Regarding the P300-Based Complex Trial Protocol for Detection of Concealed Information
Confirms CTP diagnostic accuracy from 75-90%, with enhancements using N200, feedback, and auxiliary tests restoring accuracy above 90%. The first independent replication by Lukács et al. (2016) corroborated the CTP's accuracy and countermeasure resistance using the probe vs. all-irrelevant comparison method [12]Verified The First Independent Study on the Complex Trial Protocol Version of the P300-Based Concealed Information Test
First independent replication of Rosenfeld's CTP, corroborating accuracy and countermeasure resistance using probe vs. all-irrelevant comparison.

Multi-Channel Integration

Research consistently demonstrates that combining multiple physiological channels produces substantially better CIT detection than any single channel alone [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues. When SCR, heart rate, respiration, and finger pulse amplitude are analyzed together, detection rates for guilty examinees can exceed 90% while maintaining the CIT's characteristically low false-positive rate [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies.

This multi-measure approach mirrors the general philosophy of modern polygraph practice, where examiners routinely monitor multiple physiological channels simultaneously. Examiners who understand the specific response patterns expected in each channel are better equipped to evaluate results. For guidance on proper documentation of multi-channel data, see our polygraph test data sheet documentation guide.

Principles of Effective Item Selection

The quality of CIT items is the single most important determinant of test validity [4]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 the CIT. An effective CIT item must satisfy three critical criteria simultaneously: it must be known to the guilty person (the detail must be something the perpetrator would certainly have perceived, encoded, and retained in memory), unknown to the innocent suspect (the detail must not have been leaked through media coverage, police questioning, or community gossip), and discriminating among alternatives (the critical item must be embedded among plausible alternatives that an innocent person cannot distinguish from the correct answer) [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues.

Developing items that meet all three criteria simultaneously requires close collaboration between the polygraph examiner and the investigative team. This collaboration should begin early in the investigation, ideally before details are disclosed during interrogation or shared with the media. Research suggests the CIT performs best with central features of the crime, especially when the test is delayed [4]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 the CIT.

Types of Crime Details Suitable for CIT Items

Effective CIT items typically involve concrete, perceptual details of the crime scene or criminal act. Research and field experience suggest the following categories work well: objects (type of weapon, specific items stolen, items left at the scene), locations (where a body was found, where stolen goods were hidden, the room where an assault occurred), actions (how a victim was restrained, method of entry, specific acts performed), victim characteristics (clothing, physical features, items possessed), temporal details (time-related information known only to those present), and sensory details (unusual sounds, smells, or visual features at the crime scene) [5]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test in Forensic Investigations
Confirms GKT extensively used in Japan since the 1950s, with field application data from Japanese police [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues.

Japanese polygraph examiners traditionally visit crime scenes and are required to be experts in crime scene analysis, treating the process of selecting key items for a CIT as an investigation within itself [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. Understanding the factors that contaminate polygraph exam results helps examiners avoid common pitfalls in item selection.

Alternative (Foil) Selection and Pre-Testing

The neutral alternatives (foils) presented alongside the critical item must be carefully chosen. They should be equally plausible (an uninformed person should consider each alternative equally likely to be correct), from the same semantic category, similar in emotional intensity, and free from investigative contamination [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues.

Pre-testing alternatives on a sample of uninformed individuals is considered best practice. If any particular alternative is chosen as "correct" by a disproportionate number of uninformed raters, it should be replaced. This plausibility testing ensures that differential responses to the critical item reflect genuine recognition rather than some incidental property of the stimulus.

Number of Items and Alternatives

Research recommends a minimum of five separate CIT items, each with at least four to six response alternatives [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. The Ben-Shakhar and Elaad (2003) meta-analysis found that when the number of CIT questions was at least six, the average effect size was 1.99, compared with 1.45 when fewer questions were used [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. More items increase statistical power and overall test reliability.

Each item should be presented multiple times (typically three to five repetitions) to ensure stable response patterns. The order of alternatives within each item should be randomized across repetitions to prevent positional effects. With five items, each having five alternatives and three repetitions, a standard CIT examination involves 75 individual stimulus presentations. Understanding how many chart runs a polygraph exam requires helps examiners plan adequate examination protocols.

Pre-Test Phase

The pre-test phase involves several critical steps. First, the examiner must review case materials and collaborate with investigators to identify suitable CIT items. Second, the examiner interviews the examinee to determine what the examinee claims to know about the crime [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. In Japan, if the examinee says they know some crime details, the examiner will not perform CITs on those details [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968.

Third, the examiner conducts a card test or similar demonstration to ensure the examinee understands the trial timing, to assess physiological response patterns, and to check the apparatus [5]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test in Forensic Investigations
Confirms GKT extensively used in Japan since the 1950s, with field application data from Japanese police. This practice test is standard in Japanese field CIT protocols and serves as both a familiarization exercise and a calibration opportunity.

Sensor Attachment and Calibration

The examiner attaches sensors to the examinee. In standard CIT practice, the examiner records several physiological measures: electrocardiography (ECG), respiratory movement, skin conductance, and pulse wave [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. Modern polygraph instruments can detect extremely small changes in electrodermal activity with high precision. For guidance on working with equipment, see our polygraph equipment trade-in programs guide and our guide on how to travel safely with polygraph equipment.

Test Administration and Item Presentation

During the test, the examiner presents each CIT question by showing the five items as possible answers (e.g., "a necklace?" "an earring?" "a watch?" "a brooch?" "a ring?"), including one correct crime-relevant item [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. The examinee is typically instructed to answer "no" to all items. Each question is repeated multiple times with randomized item order.

Pacing is critical — there must be sufficient inter-stimulus intervals (typically 10–15 seconds) to allow physiological responses to return to baseline between items. Examiners must also monitor for signs of fatigue and manage the examination length appropriately.

Post-Test Evaluation

After chart collection, the examiner evaluates whether the examinee showed differential responses based on the charts, examining the difference between mean responses to crime-relevant and irrelevant items and the consistency of response differences across repetitions [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. In Japan, an examiner only decides on whether an examinee recognizes each crime-relevant item and never integrates results across multiple CIT questions to judge guilt or innocence — that integration is the investigators' task [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968.

Quality of examination should be subject to polygraph peer review to maintain high standards and ensure consistency across examiners.

Meta-Analytic Findings

Major meta-analyses of CIT research provide robust evidence for the technique's validity. Ben-Shakhar and Elaad (2003) covered 80 laboratory studies with 169 experimental conditions and 5,198 participants, reporting an overall average effect size (Cohen's d) of 1.55 for SCR [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. Studies using mock-crime paradigms produced an even higher average effect size of 2.09, and under optimal conditions the effect size reached 3.12 [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants.

The Meijer, Klein Selle, Elber, and Ben-Shakhar (2014) meta-analysis extended this work to four physiological measures: SCR (d* = 1.55), respiration line length (d* = 1.11), heart rate (d* = 0.89), and P300 (d* = 1.89) [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. The CIT's false-positive rate remains extremely low — approximately 5% across studies — making it particularly valuable for protecting innocent suspects [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies.

Motivation to avoid detection, which is high in real-life investigations, was generally associated with increased CIT detection efficiency in laboratory studies [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. This suggests the CIT should perform even better in realistic investigations than in laboratory experiments [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies.

Field Validity

While published field data are relatively scarce compared to laboratory studies, the response patterns of various physiological measures in field CITs are similar to those observed in laboratory CITs — including skin conductance increase, heart rate decrease, respiration suppression, and finger pulse volume decrease for critical items compared to non-critical items [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968.

Japanese field studies by Hira and Furumitsu (2002) documented that the GKT has been extensively and successfully used in Japanese criminal investigations since the 1950s [5]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test in Forensic Investigations
Confirms GKT extensively used in Japan since the 1950s, with field application data from Japanese police. Osugi (2018) provided detailed field findings from the CIT in Japan, describing why and how the CIT is applied effectively in criminal investigations across the country [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues [7]Verified Field Findings From the Concealed Information Test in Japan
Confirms detailed field CIT data from Japan including searching CIT methodology and question-focused judgment. Nakayama (2002) further documented Japan's standardized CIT procedures in cases involving murder, arson, and theft [13]Verified Practical Use of the Concealed Information Test for Criminal Investigation in Japan
Documented Japan's routine operational use of CIT in criminal investigations including murder, arson, and theft. The well-controlled Japanese polygraph technique has been reported to achieve accuracy rates of approximately 90% for diagnoses [14]Verified Development of the Polygraph Technique in Japan for Detection of Deception
Confirms over 5,000 polygraph examinations per year in Japan with ~90% accuracy rate, and court acceptance of results.

Physical and Mental Countermeasures

Studies by Ben-Shakhar and Dolev (1996) and Honts, Devitt, Winbush, and Kircher (1996) demonstrated that mental countermeasures reduced SCR detection efficiency but did not eliminate detection entirely [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants [16]Verified Psychophysiological Detection Through the Guilty Knowledge Technique: Effects of Mental Countermeasures
Confirms mental countermeasures significantly reduced SCR detection efficiency in the CIT. Importantly, no countermeasure effects were observed when respiration line length (RLL) or heart rate (HR) were used as the detection measures [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants [16]Verified Psychophysiological Detection Through the Guilty Knowledge Technique: Effects of Mental Countermeasures
Confirms mental countermeasures significantly reduced SCR detection efficiency in the CIT. This response fractionation — where different measures show different vulnerability to countermeasures — suggests that using multiple physiological channels provides built-in protection against countermeasure attempts.

Physical countermeasures (such as biting the tongue during control items) and mental countermeasures (recalling emotional memories or performing cognitive tasks during control item presentation) both aim to increase responses to neutral items, thereby masking the differential response to the critical item [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. Research using covert respiration measures hidden in the examination chair found that physical countermeasures lowered SCR accuracy but had relatively small effects on other standard measures [16]Verified Psychophysiological Detection Through the Guilty Knowledge Technique: Effects of Mental Countermeasures
Confirms mental countermeasures significantly reduced SCR detection efficiency in the CIT. For more on this topic, see our guide on whether polygraph examiners can detect countermeasures.

P300-Based Countermeasure Resistance

The Complex Trial Protocol (CTP) developed by Rosenfeld et al. (2008) was specifically designed to resist countermeasures that defeated earlier P300 CIT methods [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy. The CTP achieved high accuracy (>90% hit rates) even when countermeasure-trained subjects attempted to defeat the test, and attempted countermeasure use was detectable via elevated reaction time [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy.

The first independent replication study by Lukács et al. (2016) corroborated the CTP's countermeasure resistance when using the probe vs. all-irrelevant comparison method, though it identified vulnerability in the probe vs. max-irrelevant comparison [12]Verified The First Independent Study on the Complex Trial Protocol Version of the P300-Based Concealed Information Test
First independent replication of Rosenfeld's CTP, corroborating accuracy and countermeasure resistance using probe vs. all-irrelevant comparison. These findings underscore the importance of using appropriate statistical comparison methods when employing the P300-based CIT.

Scale and Infrastructure

Japan is the only country in the world where the Concealed Information Test is applied on a large scale [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. The CIT is the only polygraph technique used in Japan — the Control Question Test is no longer applied [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. About 100 professional polygraph examiners conduct approximately 5,000 CIT examinations annually across the country's 47 prefectural police headquarters [5]Verified Polygraphic Examinations in Japan: Application of the Guilty Knowledge Test in Forensic Investigations
Confirms GKT extensively used in Japan since the 1950s, with field application data from Japanese police [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968.

All examiners are assigned to forensic science laboratories within prefectural police headquarters and complete a three-month training course at the Forensic Science Training Center, affiliated with the National Research Institute of Police Science (NRIPS) [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. The NRIPS, established in 1948, has been central to Japan's forensic science capabilities, with polygraph training beginning in 1953 when the Keeler model 302 polygraph was first introduced to Japan [14]Verified Development of the Polygraph Technique in Japan for Detection of Deception
Confirms over 5,000 polygraph examinations per year in Japan with ~90% accuracy rate, and court acceptance of results. Examiner trainees are selected from university graduates majoring in psychology or related fields [14]Verified Development of the Polygraph Technique in Japan for Detection of Deception
Confirms over 5,000 polygraph examinations per year in Japan with ~90% accuracy rate, and court acceptance of results.

Court Acceptance and Legal Status

The Supreme Court of Japan acknowledged that a polygraph examination report had probative force of evidence in 1964, and formally admitted polygraph results as evidence in 1968 [14]Verified Development of the Polygraph Technique in Japan for Detection of Deception
Confirms over 5,000 polygraph examinations per year in Japan with ~90% accuracy rate, and court acceptance of results [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. While the results are rarely dealt with directly in court — only a few of the approximately 5,000 annual cases are discussed each year — the CIT result showing that a defendant knows a crime-relevant fact can serve as reference information for the judge's determination [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968.

Japanese courts have focused on whether differential responding to crime-relevant facts could be explained by means other than memory obtained through perpetration [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. This judicial approach aligns well with the CIT's theoretical foundation — it asks a scientific question (does the person recognize this detail?) rather than a moral one (is the person lying?).

Unique Features of the Japanese CIT

The Japanese CIT has several distinctive features. First, examiners make intensive use of "searching questions" — CIT items where the examiner does not know which alternative is the correct answer, using the examinee's responses to discover new investigative leads [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. Second, Japanese examiners apply question-focused judgment, making individual decisions about recognition for each CIT question rather than integrating across questions [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. Third, Japanese polygraph examiners primarily judge differences in autonomic responses by visual inspection, which has been repeatedly confirmed to produce sufficiently high discrimination performance [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968.

These features enable Japanese investigators to address the problem of information leakage and use the CIT as a tool for both verification and discovery [6]Verified Memory Detection: Theory and Application of the Concealed Information Test (Book)
Comprehensive edited volume covering CIT theoretical foundations, laboratory research, field applications in Japan, countermeasures, and legal issues. For a comprehensive exploration, visit our history of polygraph use in Japan guide.

The P300 as a Recognition Signal

The P300 is a positive-going event-related potential (ERP) elicited approximately 300–600 milliseconds post-stimulus by rare and/or meaningful information [7]Verified Field Findings From the Concealed Information Test in Japan
Confirms detailed field CIT data from Japan including searching CIT methodology and question-focused judgment. In the CIT context, recognized crime items produce enhanced P300 amplitudes compared to unrecognized neutral items. Mere recognition of familiar faces and autobiographical information has been shown to suffice to elicit a larger P300, confirming that recognition plays a fundamental role in the P300-based CIT [7]Verified Field Findings From the Concealed Information Test in Japan
Confirms detailed field CIT data from Japan including searching CIT methodology and question-focused judgment.

The P300-based CIT has generated substantial research interest because it measures brain activity more directly than peripheral physiological measures and may be more resistant to certain countermeasures [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy. A 2025 meta-analysis including 54 experimental studies found a large mean effect size of 1.59 for the P300, with complex trial protocols maximizing effect sizes [8]Verified Decoding Deception with the P300: A Meta-Analysis of the Concealed Information Test
Confirms large mean effect size (d*=1.59) for P300 across 54 studies, with Complex Trial Protocols maximizing effect sizes. Wojciechowski (2014) found that while P300 potential recording shows promising results, its efficiency in field applications may not yet significantly exceed standard polygraph examinations [17]Verified Detection of concealed information with the P300 potential amplitude analysis
Found P300 recording does not attain significantly higher efficiency than polygraph examinations, though results are promising.

The Complex Trial Protocol (CTP)

The Complex Trial Protocol (CTP) was developed by J. Peter Rosenfeld and colleagues at Northwestern University in 2008 and represents the most validated countermeasure-resistant P300-based CIT method [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy [11]Verified Review of Recent Studies and Issues Regarding the P300-Based Complex Trial Protocol for Detection of Concealed Information
Confirms CTP diagnostic accuracy from 75-90%, with enhancements using N200, feedback, and auxiliary tests restoring accuracy above 90%. In each CTP trial, a rare probe or frequent irrelevant stimulus appears in the same trial in which a target or non-target later appears — the subject responds to each in succession, and this dual-stimulus design is what gives the protocol its name [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy.

More than a dozen studies of the CTP have been published since its introduction, and it has been fairly consistently proven to provide high accuracy and strong resistance to countermeasures [11]Verified Review of Recent Studies and Issues Regarding the P300-Based Complex Trial Protocol for Detection of Concealed Information
Confirms CTP diagnostic accuracy from 75-90%, with enhancements using N200, feedback, and auxiliary tests restoring accuracy above 90% [12]Verified The First Independent Study on the Complex Trial Protocol Version of the P300-Based Concealed Information Test
First independent replication of Rosenfeld's CTP, corroborating accuracy and countermeasure resistance using probe vs. all-irrelevant comparison. The CTP currently requires specialized EEG equipment not typically available in standard polygraph laboratories and is used primarily in research settings rather than operational forensic practice.

Item Quality Assurance

Examiners should pre-test all alternatives on uninformed individuals to verify equal plausibility. Each CIT examination should include at least five separate items with at least five alternatives each [2]Verified Current Research and Potential Applications of the Concealed Information Test: An Overview
Confirms CIT's strong theoretical foundation in orienting response theory and ~5% false positive rate across studies [3]Verified The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review
Confirms average effect size of 1.55 across 80 studies, 3.12 under optimal conditions, covering 5,198 participants. Items should focus on central, salient crime features with high encoding probability [4]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 the CIT. Close collaboration with investigators from the earliest stages of the case is essential to preserve holdback information suitable for CIT use.

The ethical responsibilities of a polygraph examiner demand that CIT items be constructed fairly and that examinees not be exposed to crime-relevant information prior to testing.

Multi-Channel Recording and Interpretation

Always record and analyze multiple physiological channels — SCR, respiration, heart rate, and finger pulse amplitude at minimum [1]Verified Memory detection with the Concealed Information Test: A meta-analysis of skin conductance, respiration, heart rate, and P300 data
Confirms effect sizes of d=1.55 for SCR, 1.11 for RLL, 0.89 for HR, and 1.89 for P300 across CIT studies. Use standardized scoring procedures and consider statistical decision methods to supplement visual inspection [15]Verified Broadening the Use of the Concealed Information Test in the Field
Confirms ~100 examiners conduct ~5,000 CIT cases per year in Japan, Supreme Court admitted CIT evidence in 1968. Document all procedures, item construction decisions, and scoring rationale thoroughly in the test data sheet.

Be aware that individual differences in physiological reactivity can affect CIT accuracy — electrodermally labile subjects are more frequently detected while stabile subjects may be less detectable [10]Verified Electrodermal Lability and Concealed Information Detection
Confirms individual differences in physiological reactivity (electrodermal lability) affect CIT detection accuracy. Monitor for countermeasure indicators including irregular respiration patterns, unusual movements, and elevated reaction times [9]Verified Development of a Countermeasure-Resistant P300-Based Concealed Information Test
Confirms the Complex Trial Protocol (CTP) was introduced by Rosenfeld to resist countermeasures, achieving high accuracy. Regular peer review of polygraph results enhances quality and credibility.

Training and Professional Development

Examiners interested in adding CIT methodology to their practice should seek training through APA-accredited programs and European Polygraph Association training programs. Understanding the complete research literature on the CIT, including both its strengths and limitations, is essential for competent administration.

For those considering a career in polygraph examination, our guide to private polygraph examiner career opportunities provides practical information on professional pathways.