What Is the Directed Lie Test (DLT)? Complete Guide

Defining the Directed Lie Test in Plain Language

The Directed Lie Test (DLT) is a specific format of polygraph examination that uses a unique type of comparison question known as a directed lie comparison question (DLC). In a standard DLT, the polygraph examiner explicitly instructs you to answer a particular question dishonestly. You know you are lying. The examiner knows you are lying. And this deliberate dishonesty creates a measurable physiological response that serves as a comparison baseline against your responses to the actual relevant questions about the issue being investigated.

For example, the examiner might say: "I'm going to ask you whether you have ever told even a small lie to avoid getting in trouble. I want you to answer 'No' to that question, even though we both know the truthful answer is 'Yes.' Everyone has done this at some point."

When you answer "No" — knowing you are being dishonest — your body produces a stress response. The polygraph instrument measures this response across your respiratory, electrodermal, and cardiovascular channels. To understand the physiological systems involved, see our guide on physiological responses when lying.

The core principle is straightforward: if you are truthful on the relevant questions (the questions about the actual issue being investigated), your body should react more strongly to the directed lie questions, because those are the only questions where you know you are being deceptive [1]Verified A Field Study of the Validity of the Directed Lie Control Question
First field validation of the directed-lie comparison question format, showing DLC was at least as accurate as probable-lie CQT with fewer false positive errors. Conversely, if you are being deceptive on the relevant questions, your body will react more strongly to those questions, because they represent a genuine threat — the real deception you are trying to conceal.

This comparison framework — measuring directed-lie reactions against relevant-question reactions — is the foundation of all comparison question polygraph techniques. What makes the DLT unique is its transparency: you are fully aware of the comparison mechanism, and the examiner does not need to rely on subtle psychological manipulation to generate your comparison responses [2]Verified Directed Lie Comparison Questions in Polygraph Testing
Laboratory comparison of directed lie vs. probable lie formats, finding DLC produced fewer false positives while maintaining detection of deception.

How the DLT Fits Into the Broader Polygraph Landscape

The DLT belongs to the family of comparison question tests (CQTs), which represent the most widely used polygraph methodology worldwide. Since its inception by John E. Reid in 1947, the CQT has remained the dominant polygraph test format [3]Verified A review of the polygraph: history, methodology and current status
Confirms CQT inception by John E. Reid in the late 1940s and its status as the most widely used polygraph test format. Reid, a lawyer from Chicago, developed the Control Question Technique while working at the Chicago Police Scientific Crime Detection Laboratory, introducing the concept of comparison (control) questions to replace the earlier Relevant/Irrelevant Question Technique [4]Verified Reid Method: Developing Probable Lie Comparison Questions
Confirms the probable lie comparison question was developed by John Reid in 1947 at the Chicago Police Scientific Crime Detection Laboratory.

In 1960, Cleve Backster built upon Reid's work by developing the Zone Comparison Technique (ZCT) and introducing a quantification system for chart analysis that made polygraph evaluation more objective [5]Verified Cleve Backster Zone Comparison Technique history
Confirms Backster developed the Zone Comparison Technique and the first numerical scoring system for polygraph chart analysis. Backster's numerical scoring system — the first polygraph interpretation system to use numerical evaluation — became a standard procedure in the field and remains widely used today [6]Verified Backster's Numerical Chart Analysis History
Confirms Backster introduced numerical scoring chart analysis circa 1960, revolutionising polygraph chart evaluation.

The directed lie comparison question was introduced by David C. Raskin of the University of Utah in the 1980s [7]Verified Utah Approach to Comparison Question Polygraph Testing
Confirms Raskin introduced the Directed Lie Control Question (DLCQ) in the 1980s at the University of Utah. Raskin, working with colleagues including Charles Robert Honts and John C. Kircher, sought to create a more standardised and scientifically rigorous alternative to the probable-lie comparison question. Their work at the University of Utah Psychology Laboratory represented a systematic effort to refine comparison question methodology through empirical research [8]Verified Utah Approach to Comparison Question Polygraph Testing — Research Overview
Confirms David Raskin began studying polygraph technique at the University of Utah in 1970 and that the Utah-CQT resulted from over 30 years of systematic research.

The 1988 field study by Honts and Raskin was the first field validation of the directed-lie comparison question format, examining 25 criminal cases and demonstrating that the DLC was at least as accurate as the probable-lie CQT with fewer false positive errors [1]Verified A Field Study of the Validity of the Directed Lie Control Question
First field validation of the directed-lie comparison question format, showing DLC was at least as accurate as probable-lie CQT with fewer false positive errors. This landmark study established the DLC as a viable alternative to the traditional probable-lie format and opened the door for widespread federal adoption.

Origins at the University of Utah

The directed lie comparison question emerged from the broader research programme conducted at the University of Utah beginning in 1970, when Dr. David Raskin started systematically studying the probable-lie comparison question polygraph technique [8]Verified Utah Approach to Comparison Question Polygraph Testing — Research Overview
Confirms David Raskin began studying polygraph technique at the University of Utah in 1970 and that the Utah-CQT resulted from over 30 years of systematic research. Raskin and his colleagues — including John C. Kircher and Charles Robert Honts — refined the elements of polygraphy to determine which aspects could be scientifically proven to increase validity and reliability.

Their efforts culminated in what is known today as the Utah approach to the Comparison Question Test (CQT), an empirically consistent and unified approach to polygraphy [8]Verified Utah Approach to Comparison Question Polygraph Testing — Research Overview
Confirms David Raskin began studying polygraph technique at the University of Utah in 1970 and that the Utah-CQT resulted from over 30 years of systematic research. The directed lie comparison question was a key innovation within this framework. Unlike the probable-lie question — which requires the examiner to carefully craft questions and subtly manipulate the examinee into lying — the directed lie question was standardised, transparent, and easier to administer consistently.

An early unpublished manuscript by Fuse (1982) documented a directed lie control testing technique [9]Verified Recent Laboratory and Field Research on Polygraph Techniques
Confirms early DLT research including Fuse (1982) unpublished manuscript and that DLT is at least as accurate as CQT with fewer false positive errors, followed by the laboratory comparison by Driscoll, Honts, and Jones (1987) in Psychophysiology that found the DLC produced fewer false positives while maintaining detection of deception [2]Verified Directed Lie Comparison Questions in Polygraph Testing
Laboratory comparison of directed lie vs. probable lie formats, finding DLC produced fewer false positives while maintaining detection of deception. This laboratory work was rapidly followed by the 1988 field study, cementing the DLC's scientific credentials.

Federal Adoption and the Test for Espionage and Sabotage

Around 1992, the Department of Defense Polygraph Institute (DoDPI) began development of an improved test for security screening [10]Verified Can we trust counterintelligence polygraph tests?
Confirms DoDPI began development of TES around 1992 and all DoD agencies switched from CSP to TES by 1994. The result was the Test for Espionage and Sabotage (TES), a directed-lie screening format that was significantly more standardised and less intrusive than older methods [11]Verified Psychophysiological Detection of Deception Accuracy Rates Using the TES
Confirms TES uses directed lie comparison questions and reports 98% accuracy for innocent and 83.3% for guilty examinees in simulation studies. Dr. Sheila D. Reed served as the principal investigator throughout the planning, data collection, and drafting of the TES studies [12]Verified DoDPI TES Study — Principal Investigator
Confirms Dr. Sheila D. Reed served as principal investigator throughout TES planning, data collection, and manuscript drafting.

The TES differed from previous counterintelligence screening formats in several important ways: it reduced the number of issues being tested, standardised the question sequence, used a brief and logical pretest, and incorporated directed lie comparison questions [12]Verified DoDPI TES Study — Principal Investigator
Confirms Dr. Sheila D. Reed served as principal investigator throughout TES planning, data collection, and manuscript drafting. By fiscal year 1994, all DoD agencies had switched from the Counterintelligence Scope Polygraph (CSP) to the TES for security screening [10]Verified Can we trust counterintelligence polygraph tests?
Confirms DoDPI began development of TES around 1992 and all DoD agencies switched from CSP to TES by 1994. In 1999, the Department of Energy adopted the TES format for its counterintelligence polygraph screening programme [13]Verified The Polygraph and Lie Detection — Appendix B: DOE and Federal Agencies
Describes the TES directed-lie screening test, DOE adoption in 1999, and directed-lie question methodology in federal use.

The NCCA (formerly DoDPI), which provides graduate-level education in polygraph to 25 federal agencies, incorporates directed-lie methodology into its curriculum [14]Verified NCCA ribbon-cutting — U.S. Army article
Confirms NCCA provides graduate-level education in polygraph to 25 federal agencies, first established in 1951 as the Army Polygraph School. In 2021, the Defense Intelligence Agency officially transferred operational control of the NCCA to the Defense Counterintelligence and Security Agency (DCSA) [15]Verified DCSA Takes Operational Control of Credibility Assessment Service Center
Confirms NCCA management transition from DIA to the Defense Counterintelligence and Security Agency (DCSA) in October 2021. Today, the NCCA oversees approximately 1,100 federally trained polygraph examiners who conduct more than 110,000 examinations per year [16]Verified DCSA Fiscal Year 2025 Budget Estimates
Confirms NCCA oversees approximately 1,100 federally trained polygraph examiners conducting more than 110,000 examinations per year.

Key Milestones in DLT Development

The development of the directed lie test followed a clear trajectory of scientific refinement:

1947: John E. Reid developed the Control Question Technique (CQT) in Chicago, introducing comparison questions to polygraph testing [3]Verified A review of the polygraph: history, methodology and current status
Confirms CQT inception by John E. Reid in the late 1940s and its status as the most widely used polygraph test format.

1960: Cleve Backster developed the Zone Comparison Technique and introduced numerical scoring for polygraph chart analysis [5]Verified Cleve Backster Zone Comparison Technique history
Confirms Backster developed the Zone Comparison Technique and the first numerical scoring system for polygraph chart analysis.

1980s: David C. Raskin introduced the Directed Lie Control Question (DLCQ) at the University of Utah [7]Verified Utah Approach to Comparison Question Polygraph Testing
Confirms Raskin introduced the Directed Lie Control Question (DLCQ) in the 1980s at the University of Utah.

1987: Driscoll, Honts, and Jones published the first laboratory comparison of directed lie vs. probable lie formats in Psychophysiology [2]Verified Directed Lie Comparison Questions in Polygraph Testing
Laboratory comparison of directed lie vs. probable lie formats, finding DLC produced fewer false positives while maintaining detection of deception.

1988: Honts and Raskin published the first field validation of the directed-lie comparison question, establishing its viability for criminal investigation [1]Verified A Field Study of the Validity of the Directed Lie Control Question
First field validation of the directed-lie comparison question format, showing DLC was at least as accurate as probable-lie CQT with fewer false positive errors.

1988: Kircher and Raskin at the University of Utah developed the Computer Assisted Polygraph System (CAPS), incorporating the first algorithm for evaluating physiological data [17]Verified Computerized Polygraph System history
Confirms Kircher and Raskin developed the Computer Assisted Polygraph System (CAPS) at the University of Utah in 1988.

1992-1995: DoDPI developed and validated the Test for Espionage and Sabotage (TES), incorporating directed lie comparison questions [12]Verified DoDPI TES Study — Principal Investigator
Confirms Dr. Sheila D. Reed served as principal investigator throughout TES planning, data collection, and manuscript drafting.

1993: Dr. Dale E. Olsen and John C. Harris at Johns Hopkins University Applied Physics Laboratory completed the PolyScore software, which used mathematical algorithms to analyse polygraph data [18]Verified PolyScore development at Johns Hopkins APL
Confirms PolyScore was developed at Johns Hopkins University Applied Physics Laboratory using logistic regression and neural network models.

2011: The APA published its meta-analytic survey of criterion accuracy, covering 38 studies and finding aggregated decision accuracy of 87% across all validated techniques [19]Verified Polygraph Validity Research — APA Meta-Analysis
Confirms APA meta-analysis of 38 studies found aggregated decision accuracy of 87% for validated techniques with 13% inconclusive rate.

2015: Honts and Reavy published their 250-participant study confirming no differences between directed-lie and probable-lie test types in countermeasure vulnerability [20]Verified Countermeasure Attempts in the Directed-Lie vs. Probable-Lie CQT
250-participant study found no differences between DL and PL test types in spontaneous countermeasure attempts; DLT has equivalent validity and is more standardized.

The Pre-Test Interview

Every polygraph examination, including the DLT, begins with a thorough pre-test interview. During this phase, the examiner explains the entire testing procedure, reviews all questions that will be asked, and ensures the examinee understands each one. This is consistent with the four-phase testing procedure used across all modern polygraph formats.

In a DLT, the examiner explicitly explains the purpose of the directed lie comparison questions. You will be told that certain questions are being included specifically so that you can demonstrate your physiological capability when answering dishonestly. The examiner will instruct you to lie to these questions and explain why this is being done. This transparency is one of the DLT's greatest strengths — there are no hidden psychological games [21]Verified Directed Lie Comparison Questions in Polygraph Examinations: History and Methodology
Confirms that DLC questions were intended to provide examinees an opportunity to demonstrate physiological capability when answering deceptively.

The examiner will also review the relevant questions about the actual issue under investigation, as well as any neutral or irrelevant questions included in the test sequence. Every question you will hear during the test is discussed beforehand.

Data Collection: The In-Test Phase

During the data collection phase, the examiner asks all questions while polygraph sensors record your physiological responses. The standard four components are used: two pneumograph tubes measuring respiration, electrodermal plates measuring skin conductance, and a cardiovascular cuff measuring blood volume changes [22]Verified The Polygraph and Lie Detection — Appendix A: Techniques
Describes directed-lie tests where examinees are instructed to respond negatively and untruthfully to comparison questions.

The test typically includes three types of questions: relevant questions (about the issue being investigated), directed lie comparison questions (which you have been instructed to answer dishonestly), and neutral or irrelevant questions (simple biographical questions that establish a baseline).

The question sequence is repeated multiple times — typically three presentations — to ensure reliable data collection. Between each presentation, the examiner may pause briefly. The entire data collection phase usually takes 15 to 25 minutes, though the full examination including pre-test and post-test can last 90 to 120 minutes.

Scoring and Decision Making

After data collection, the examiner evaluates the physiological recordings using one or more validated scoring methods. The Utah Numerical Scoring System, developed by Bell, Raskin, Honts, and Kircher, provides a standardised framework for comparing reactions to directed lie questions against reactions to relevant questions [23]Verified Manually Scoring Polygraph Charts Utilizing the Seven-Position Numerical Scoring System
Describes the Utah Numerical Scoring System used for DLT and CQT chart evaluation.

Modern polygraph systems also offer computerised scoring algorithms. The Computerized Polygraph System (CPS), developed by Raskin and Kircher at the University of Utah, uses discriminant analysis to weigh and combine physiological measures [17]Verified Computerized Polygraph System history
Confirms Kircher and Raskin developed the Computer Assisted Polygraph System (CAPS) at the University of Utah in 1988. The PolyScore algorithm, developed at Johns Hopkins University Applied Physics Laboratory, uses logistic regression or neural network models to estimate the probability of deception [18]Verified PolyScore development at Johns Hopkins APL
Confirms PolyScore was developed at Johns Hopkins University Applied Physics Laboratory using logistic regression and neural network models. The Objective Scoring System (OSS-3), bundled with Lafayette LXSoftware, provides another validated algorithmic approach [24]Verified Lafayette LXSoftware with OSS-3
Confirms LXSoftware includes Objective Scoring System (OSS) and PolyScore algorithms for polygraph analysis.

For automated scoring in modern polygraph analysis, these algorithms complement human evaluation by providing consistent, objective analysis of the physiological data.

If the comparison question reactions are significantly larger than the relevant question reactions, the result is classified as Not Deceptive (truthful). If the relevant question reactions are significantly larger, the result is classified as Deceptive. If the differences are not sufficiently clear, the result may be classified as Inconclusive.

Probable-Lie vs. Directed-Lie Comparison Questions

The fundamental difference between the DLT and the traditional CQT lies in how comparison questions are constructed and presented. In a probable-lie CQT, the examiner formulates questions about past behaviour that the examinee is likely to lie about — but the examinee is not told to lie. The comparison questions deal with issues concerning the examinee's moral character and are designed to be "formulated and asked in a way that is intended to subtly prompt the examinee to answer them with 'no'" [25]Verified ResearchGate — David C. Raskin research profile
Confirms directed-lie test as a variant CQT where examiner instructs the examinee to answer 'no' to all comparison questions. This requires considerable examiner skill and creates variability between examiners.

In the DLT, the comparison mechanism is completely transparent. The examinee is explicitly told: "I want you to lie to this question." There is no ambiguity, no subtle manipulation, and no dependence on the examiner's ability to craft psychologically effective comparison questions [21]Verified Directed Lie Comparison Questions in Polygraph Examinations: History and Methodology
Confirms that DLC questions were intended to provide examinees an opportunity to demonstrate physiological capability when answering deceptively. The original designers intended the DLC to provide examinees an opportunity to demonstrate physiological capability when answering dishonestly, while providing additional motivation to remain alert throughout the examination [21]Verified Directed Lie Comparison Questions in Polygraph Examinations: History and Methodology
Confirms that DLC questions were intended to provide examinees an opportunity to demonstrate physiological capability when answering deceptively.

Pamela K. Shaw's 2012 comprehensive review found "little to no meaningful difference in detection accuracy between directed lie and probable lie comparison questions" [26]Verified The Empirical Basis for the Use of Directed Lie Comparison Questions in Diagnostic and Screening Polygraphs
Found little to no meaningful difference in detection accuracy between directed lie and probable lie comparison questions, supporting the scientific validity of DLCQs in both diagnostic and screening contexts.

Standardisation and Examiner Independence

One of the most significant advantages of the DLT is its inherent standardisation. Because the directed lie questions follow a consistent format, the DLT reduces the variability that can occur when different examiners construct probable-lie questions differently. The Honts and Reavy (2015) study of 250 participants confirmed that while the probable-lie and directed-lie variants produced equivalent results in detection accuracy, the directed-lie variant "has much to recommend it as it is inherently more standardized in its administration" [20]Verified Countermeasure Attempts in the Directed-Lie vs. Probable-Lie CQT
250-participant study found no differences between DL and PL test types in spontaneous countermeasure attempts; DLT has equivalent validity and is more standardized.

This standardisation is particularly valuable in large-scale screening programmes where consistency across thousands of examinations is essential. The TES format, for example, specifies exact directed lie questions from an approved list and requires that examiners follow the same procedures [12]Verified DoDPI TES Study — Principal Investigator
Confirms Dr. Sheila D. Reed served as principal investigator throughout TES planning, data collection, and manuscript drafting. This level of consistency would be difficult to achieve with probable-lie comparison questions, which must be individually tailored to each examinee.

For examinees, this standardisation means a more predictable and transparent testing experience. The role of examiner intuition remains important in interpreting results, but the DLT reduces the degree to which the outcome depends on any single examiner's questioning technique.

Field and Laboratory Accuracy Data

The scientific evidence supporting the directed lie test is robust. The APA's 2011 meta-analytic survey of 38 studies found that the combination of all validated polygraph techniques produced an aggregated decision accuracy of 87%, with an inconclusive rate of 13% [19]Verified Polygraph Validity Research — APA Meta-Analysis
Confirms APA meta-analysis of 38 studies found aggregated decision accuracy of 87% for validated techniques with 13% inconclusive rate. Single-issue diagnostic techniques achieved 89% accuracy, while multiple-issue screening techniques achieved approximately 85% [27]Verified APA Meta-Analysis — Accuracy by Test Type
Confirms single-issue techniques achieve 89% accuracy and that DLST/TES formats meet APA boundary requirements for validated accuracy.

Specifically regarding the DLT, Raskin and colleagues demonstrated through laboratory and field research that the DLT is at least as accurate as the CQT, produces fewer false positive errors, and is simpler to construct and administer [28]Verified Recent Laboratory and Field Research on Polygraph Techniques — DLT accuracy
Confirms DLT is at least as accurate as CQT, produces fewer false positive errors, and is simpler to construct and administer. The landmark 1988 Honts and Raskin field study confirmed DLC accuracy in real criminal cases with independently verified outcomes [1]Verified A Field Study of the Validity of the Directed Lie Control Question
First field validation of the directed-lie comparison question format, showing DLC was at least as accurate as probable-lie CQT with fewer false positive errors.

Brandon G. Bell, John C. Kircher, and Peter C. Bernhardt (2008) demonstrated that new physiological measures could further improve directed-lie test accuracy in mock crime scenarios, addressing previous limitations where respiration measures were less diagnostic in the directed-lie format [29]Verified New measures improve the accuracy of the directed-lie test when detecting deception using a mock crime
New physiological measures improved directed-lie test accuracy in mock crime scenarios, addressing previous limitations with respiration measures. These findings show the DLT continues to evolve and improve.

The DLST/TES scored with the seven-position TDA model and the DLST/TES scored with the Empirical Scoring System (ESS) are both among the techniques meeting APA boundary requirements for validated accuracy [30]Verified APA Validated Techniques FAQ
Confirms DLST/TES scored with TDA model and ESS are among techniques meeting APA boundary requirements, and that the APA does not 'approve' techniques but summarises research.

Countermeasure Resistance

A common concern is whether the DLT might be more vulnerable to countermeasures because examinees know which questions are the directed lies. Research does not support this concern.

The 250-participant study by Honts and Reavy (2015) found no differences between directed-lie and probable-lie test types in spontaneous countermeasure attempts, confirming that the DLT format is not more vulnerable [20]Verified Countermeasure Attempts in the Directed-Lie vs. Probable-Lie CQT
250-participant study found no differences between DL and PL test types in spontaneous countermeasure attempts; DLT has equivalent validity and is more standardized. Additional research by Honts, Handler, Shaw, and Gougler (2015) suggests that directed-lie formats may actually be more robust against deliberate manipulation [31]Verified Directed Lie Comparison Questions and Countermeasure Resistance
Research suggests modern testing formats with directed lies may be more robust against deliberate manipulation attempts.

Separate research by Honts (2002) found that some countermeasure behaviours produce distinctive physiological patterns that can be detected by experienced examiners [32]Verified Detection of Subjects Employing Directed Countermeasures on the Comparison Question Test
Found that some countermeasure behaviours produced distinctive physiological patterns detectable by experienced examiners. This means that even when individuals attempt to manipulate their results, trained polygraph professionals can often identify the interference.

The seriousness with which federal authorities treat countermeasure attempts is demonstrated by enforcement actions. In 2015, Doug Williams was convicted on multiple counts of mail fraud and witness tampering for teaching polygraph countermeasures to undercover agents [33]Verified Doug Williams (polygraph critic) - Wikipedia
Confirms Williams was convicted in 2015 on mail fraud and witness tampering charges for teaching polygraph countermeasures to undercover agents. For more on the topic of substances and polygraph accuracy, see our guide on whether Xanax can affect a polygraph test.

Research on emerging technologies like fMRI has shown that cognitive countermeasures can reduce memory decoding accuracy to chance-level performance [34]Verified Goal-directed modulation of neural memory patterns: Implications for fMRI-based memory detection
Demonstrated cognitive countermeasures reduced fMRI memory decoding from reliable detection to chance-level performance, highlighting the importance of continued research into countermeasure detection across all credibility assessment tools.

Federal Government Applications

The directed lie format is now integral to U.S. federal polygraph programmes. The Test for Espionage and Sabotage (TES) is the primary counterintelligence-scope polygraph screening format used by the U.S. Departments of Defense and Energy [13]Verified The Polygraph and Lie Detection — Appendix B: DOE and Federal Agencies
Describes the TES directed-lie screening test, DOE adoption in 1999, and directed-lie question methodology in federal use. The TES covers critical security topics including espionage, sabotage, terrorism, unauthorised disclosure of classified information, and unauthorised foreign contacts [35]Verified The Polygraph and Lie Detection — Appendix B: DOE Polygraph Screening
Confirms DOE counterintelligence polygraph covers espionage, sabotage, terrorism, unauthorised disclosure, and foreign contacts using TES format.

The NCCA, now under the Defense Counterintelligence and Security Agency (DCSA) [15]Verified DCSA Takes Operational Control of Credibility Assessment Service Center
Confirms NCCA management transition from DIA to the Defense Counterintelligence and Security Agency (DCSA) in October 2021, provides training and oversight for federal polygraph programmes. Only nine of the 25 agencies the NCCA supports are defense organisations — the remainder span the full range of federal agencies requiring polygraph capability [14]Verified NCCA ribbon-cutting — U.S. Army article
Confirms NCCA provides graduate-level education in polygraph to 25 federal agencies, first established in 1951 as the Army Polygraph School. U.S. Customs and Border Protection has also adopted a TES-based format — the Test for Espionage, Sabotage, and Corruption (TES-C) — for pre-employment screening [36]Verified U.S. Customs and Border Protection TES-C Documentation
Confirms CBP adopted a TES-based directed-lie format (TES-C) for pre-employment polygraph screening. Learn more about federal polygraph requirements in our guides to the ATF polygraph test and Border Patrol polygraph.

Law Enforcement and Private Sector

Beyond federal applications, directed lie comparison questions are used in law enforcement pre-employment screening, criminal investigations, and private sector examinations. Many state and local law enforcement agencies use DLC-based formats for pre-employment polygraph testing, following the methodology taught at APA-accredited schools that mirrors NCCA training.

In the private sector, DLT methodology is commonly used in specific-issue examinations including infidelity testing, theft investigations, and business polygraph testing. The DLT's transparency makes it particularly well-suited for private examinations, where building trust with the examinee is essential.

Directed lie comparison questions are also commonly incorporated into Post-Conviction Sex Offender Testing (PCSOT) polygraph formats. Both monitoring and maintenance polygraph tests in sex offender management programmes may use DLC questions, as the format's standardisation and transparency support the therapeutic goals of these programmes.

International Use

The directed lie format has gained international adoption alongside the broader spread of polygraph testing. A 2021 meta-analysis by Honts and colleagues identified resident polygraph examiners in 65 countries, with 24 professionally recognised training schools and 12 professional organisations with international memberships [37]Verified A comprehensive meta-analysis of the comparison question polygraph test
Identified polygraph examiners in 65 countries with 24 training schools and 12 professional organisations; APA has 2,800+ members from 58 countries. Many of these programmes incorporate directed-lie methodology.

The American Polygraph Association, with more than 2,800 members from 58 countries [37]Verified A comprehensive meta-analysis of the comparison question polygraph test
Identified polygraph examiners in 65 countries with 24 training schools and 12 professional organisations; APA has 2,800+ members from 58 countries, has included DLC-based techniques in its standards and training requirements. International polygraph training programmes in countries from the UK to Southeast Asia frequently teach directed lie methodology. To explore the global spread of polygraph testing, see our guides on polygraph history in India and polygraph in Southeast Asia.

Before Your Examination

If you are scheduled for a polygraph examination that uses the DLT format, preparation is straightforward. You do not need to study or memorise anything — the examiner will explain everything during the pre-test interview. Arrive well-rested, avoid excessive caffeine, and be prepared for an examination that typically lasts 90 to 120 minutes in total.

The most important thing to understand is that the directed lie questions are not tricks. They are a scientifically validated component of the test designed to measure your physiological capability when you know you are lying. Following the examiner's instructions on these questions is essential for a valid result.

For couples considering polygraph testing, learn more about the process in our guide to lie detector tests for couples. If your partner has requested you take a test, our guide on what to expect when asked to take a polygraph provides helpful context.

During the Test

During the examination itself, you will be seated comfortably with pneumograph tubes around your chest and abdomen, electrodermal sensors on your fingers, and a cardiovascular cuff on your arm. The examiner will ask the questions that were reviewed during the pre-test, and you will answer each one with a simple "Yes" or "No."

When a directed lie comparison question comes up — for example, "Did you ever say something you later regretted?" — you will answer "No" as instructed, even though both you and the examiner know the truthful answer is "Yes." This deliberate lie produces a measurable physiological reaction that serves as the comparison baseline.

Between each presentation of the question sequence, the examiner may briefly pause. You will typically hear the full question sequence three times. Throughout the process, sit still, breathe normally, and focus on the questions. The examiner will guide you through every step.

After Your Examination

Following data collection, the examiner will analyse the charts and provide you with the results. Depending on the context of the examination, you may receive a verbal result immediately or a written report may be prepared.

If you are accused of something you did not do, a polygraph examination using the DLT format can be a powerful tool for demonstrating your truthfulness. Learn more about how a UK polygraph test can clear your name or how a polygraph can support your DUI defense strategy.

Academic Discussion of DLC Limitations

Like all scientific methodologies, the directed lie test has been subject to scholarly scrutiny. Nathan J. Gordon's 2015 theoretical analysis in the European Polygraph questioned whether DLC adoption represents genuine scientific advancement, noting concerns about potential oversimplification of the comparison question mechanism [38]Verified A Theoretical Analysis of the Directed Lie Question (DLC)
Questions whether DLC adoption represents genuine scientific advancement or a problematic simplification.

Shurany and Gordon (2021) reported that 28.6% of directed lie questions failed to provoke physiological reactions during stimulation tests, and a small number of examinees refused to lie as directed [39]Verified Directed Lie – The Correct or the Easy Way?
Found 28.6% of directed lie questions failed to provoke reactions during stimulation tests; some examinees refused to lie as directed. These findings highlight the importance of proper pre-test instruction and examiner skill in ensuring directed lie questions function as intended.

However, the weight of evidence strongly supports the DLT. The Shaw (2012) comprehensive review confirmed equivalent accuracy between directed lie and probable lie formats [26]Verified The Empirical Basis for the Use of Directed Lie Comparison Questions in Diagnostic and Screening Polygraphs
Found little to no meaningful difference in detection accuracy between directed lie and probable lie comparison questions, and the large-scale Honts and Reavy (2015) study demonstrated equivalent validity with superior standardisation [20]Verified Countermeasure Attempts in the Directed-Lie vs. Probable-Lie CQT
250-participant study found no differences between DL and PL test types in spontaneous countermeasure attempts; DLT has equivalent validity and is more standardized. The APA's inclusion of DLC-based techniques among validated formats reflects the scientific consensus that the DLT is a sound and effective polygraph methodology [19]Verified Polygraph Validity Research — APA Meta-Analysis
Confirms APA meta-analysis of 38 studies found aggregated decision accuracy of 87% for validated techniques with 13% inconclusive rate.