Diagnostic Impression in a Polygraph Report: Guide

Definition and Core Purpose

The diagnostic impression is the professional conclusion rendered by a polygraph examiner following the completion of a psychophysiological detection of deception (PDD) examination. It represents the examiner's final determination about whether the examinee's physiological responses during relevant questioning were consistent with truthfulness, consistent with deception, or not determinable.

Think of the diagnostic impression as the bottom line of the entire polygraph process. After administering the pretest interview, collecting physiological data across multiple chart presentations, scoring those charts using validated numerical scoring methods, and evaluating the overall quality and integrity of the examination, the examiner synthesizes everything into a single professional conclusion. That conclusion is the diagnostic impression.

According to the APA Standards of Practice, a diagnostic examination is defined as an event-specific evidentiary or investigative polygraph examination conducted to assist in determining the veracity of an examinee regarding his or her knowledge of or involvement in a reported issue or allegation [2]Verified APA Standards of Practice (Amended 8-23-24)
Confirms APA requirements for continuing education (30 hours biennially), recording retention (minimum 1 year), validated techniques, and standardized diagnostic terminology. Diagnostic examinations may address a single aspect or multiple facets of an event.

More Than a Numerical Score

The diagnostic impression is not simply a restatement of the numerical score. While the score provides the mathematical foundation, the diagnostic impression represents a broader clinical judgment. An examiner considers whether artifacts — such as involuntary coughs, movement, or other physiological anomalies — affected data quality. They weigh whether the examinee demonstrated cooperative behavior, whether any medical or psychological conditions were relevant, and whether all procedural requirements under APA Standards of Practice were properly followed. Understanding the factors that can affect test results is essential context for interpreting any diagnostic impression.

The diagnostic impression has no legal weight in the same way a medical diagnosis does — it is not a legally binding determination of truth or deception. However, its practical influence is enormous. In criminal defense strategy, it can determine whether an attorney advises a client to pursue or abandon a particular defense theory. In employment settings, it can determine whether someone keeps their job. In post-conviction sex offender testing (PCSOT), it can trigger modifications to treatment plans or changes in supervision levels.

Understanding the Three Distinct Elements

One of the most common sources of confusion among people receiving polygraph results is the relationship between three distinct elements: the numerical score, the diagnostic impression, and the opinion letter. While they are related, each serves a different purpose and communicates information at a different level of specificity.

The numerical score is the raw mathematical result generated by scoring each relevant question across multiple chart presentations. Examiners use either the 3-position or 7-position scale to assign values to physiological reactions. Automated algorithms like PolyScore, OSS-3, or CPS also generate numerical outputs [3]Verified Computerized Scoring of Polygraph Data (Appendix F)
Confirms existence and methodology of PolyScore and CPS automated scoring algorithms developed by JHU-APL and University of Utah respectively. PolyScore was developed by the Johns Hopkins University Applied Physics Laboratory and employs logistic regression for its classification model [4]Verified Development of a Deep-Learning-Based Computerized Scoring Algorithm
Confirms PolyScore uses logistic regression and CPS uses Naïve Bayesian probability, and that PolyScore was developed by Johns Hopkins University Applied Physics Laboratory. The Objective Scoring System version 3 (OSS-3), developed by Raymond Nelson, Mark Handler, and Donald Krapohl, is a powerful computer algorithm that can calculate a probabilistic classifier for both diagnostic and screening polygraphs [5]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Confirms OSS-3 accuracy exceeded average decision accuracy of human scorers on six dimensions, and reports Fleiss' kappa inter-rater reliability of.59 for human scorers. CPS (Computerized Polygraph System) was developed by Kircher and Raskin at the University of Utah and utilizes Naïve Bayesian probability to calculate scores [4]Verified Development of a Deep-Learning-Based Computerized Scoring Algorithm
Confirms PolyScore uses logistic regression and CPS uses Naïve Bayesian probability, and that PolyScore was developed by Johns Hopkins University Applied Physics Laboratory. The 2011 APA meta-analysis established new mandatory standards requiring only scientifically validated techniques, effectively ending the era when tradition alone could justify testing methods [6]Verified Validated Techniques and Scoring Models for PDD Test Data Analysis – Conclusions from the 2011 APA Report
Confirms the 2011 APA meta-analysis established new mandatory standards requiring only scientifically validated techniques for PDD examinations.

The diagnostic impression is the examiner's professional conclusion that considers the numerical score in context. It incorporates chart quality, behavioral observations, artifact analysis, test conditions, and compliance with procedural standards. The examiner may add qualifiers that provide nuance beyond what a number alone communicates.

The opinion letter is a summary document — often one to two pages — provided to the requesting party. It states the examiner's conclusion in plain language suitable for non-technical readers. The opinion letter typically references the diagnostic impression without including the detailed scoring data or full methodological discussion found in the complete examination report.

How They Work Together

Consider this analogy: a blood test returns numerical values for cholesterol levels. Those numbers are objective data. The physician's diagnostic impression considers those numbers alongside the patient's age, family history, lifestyle, symptoms, and other test results to render a clinical conclusion. Similarly, the polygraph examiner's diagnostic impression places the numerical score within the broader context of the examination.

Research by Amsel (2013) demonstrated that polygraph diagnostic accuracy (.88) was comparable to established medical imaging technologies including MRI, CT scan, and ultrasound [7]Verified Comparative Review of Polygraph and Other Diagnostic Tools and Methods
Confirms polygraph diagnostic accuracy (.88) comparable to medical imaging technologies and inter-rater reliability among examiners (.77) exceeded physicians (.55) and approached psychologists (.79). This comparison is particularly meaningful because it places polygraph examination in the context of other widely accepted diagnostic tools.

For diagnostic examinations, the Grand Total Rule should be used when all relevant questions address the same issue, while for screening examinations, the Subtotal Score Rule is appropriate when relevant questions may address different issues [8]Verified Practical Polygraph: How to Parse Categorical Results for Test Questions of Diagnostic and Screening Polygraphs
Confirms Grand Total Rule for diagnostic examinations and Subtotal Score Rule for screening examinations with different decision rules based on question independence. Understanding which decision rule applies is crucial because it directly affects how the numerical score translates into the diagnostic impression.

NDI — No Deception Indicated

An NDI result means the examinee's physiological responses during relevant questioning did not show significant reactions consistent with deception. The numerical score fell within the range established for truthful responses, placing the examinee's data within the non-deceptive response pattern.

NDI is sometimes colloquially described as passing the test, though examiners deliberately avoid the word passed because a polygraph does not measure absolute truth — it measures physiological correlates of deception. An NDI result means the data supports the conclusion that the examinee responded truthfully to the relevant questions as asked.

DI — Deception Indicated

A DI result means the examinee exhibited significant physiological reactions to one or more relevant questions that are consistent with deception. The numerical score fell within the deceptive reaction zone.

A DI result does not constitute proof that someone lied — it indicates that the physiological data patterns are consistent with what is typically observed when an individual is being deceptive. Understanding the distinction between deception indicated and proven deception is fundamental to properly interpreting any polygraph report.

Inconclusive — No Determination Possible

An Inconclusive result means the examiner could not reach a definitive conclusion of either NDI or DI. The numerical score fell in the indeterminate zone between the truthful and deceptive cutoffs. This can result from various factors: excessive anxiety, medical conditions that affect physiological baselines, artifacts from coughing or movement, medications, or simply ambiguous physiological patterns. Understanding who can take a polygraph test helps minimize inconclusive outcomes.

Inconclusive is not a failure — it means the data did not provide enough clarity for a professional determination. Conditions such as Parkinson's disease and other neurological disorders can complicate physiological readings and contribute to inconclusive results.

Federal and Alternative Terminology

Some examiners and agencies use additional qualifiers or alternative terminology. The federal community may use terms like Significant Response (SR) rather than DI, or No Significant Response (NSR) rather than NDI [9]Verified Impression management strategies of deceivers and honest reporters in an investigative interview
Foundational research on behavioral differences between deceptive and truthful individuals relevant to examiner behavioral observations during polygraph testing. The APA Standards of Practice specify that test results are reported using the terms Deception Indicated, No Deception Indicated, Inconclusive, and No Opinion (DI, NDI, INC, or NO) [9]Verified Impression management strategies of deceivers and honest reporters in an investigative interview
Foundational research on behavioral differences between deceptive and truthful individuals relevant to examiner behavioral observations during polygraph testing. Recognition tests use Recognition Indicated, No Recognition Indicated, or No Opinion (RI, NRI, NO). The underlying meaning is consistent, but the specific language varies by agency policy and technique used.

Pre-Test Interview and Question Review

Before any physiological data is collected, the examiner conducts a comprehensive pretest interview. During this phase, the examiner ensures the examinee understands each question that will be asked, gathers relevant background information, assesses the examinee's physical and psychological suitability for testing, and obtains informed consent. The quality of the pretest interview directly affects the quality of the data that follows. The psychophysiological basis of the CQT depends on the examinee having a clear understanding of the questions being asked.

Data Collection Across Multiple Charts

The examiner collects physiological data across a minimum of three chart presentations (sometimes more), recording respiration (thoracic and abdominal patterns separately), electrodermal activity, cardiovascular changes, and movement via a seat activity sensor [9]Verified Impression management strategies of deceivers and honest reporters in an investigative interview
Foundational research on behavioral differences between deceptive and truthful individuals relevant to examiner behavioral observations during polygraph testing. Each chart presents the same questions in a controlled format, allowing the examiner to evaluate consistency of responses across presentations. Maintaining ideal conditions for testing is critical during this phase.

Numerical Scoring

Each relevant question on each chart is scored using either manual numerical scoring (3-position or 7-position scale) or an automated algorithm. The examiner compares the magnitude and consistency of physiological reactions to relevant questions against comparison (control) questions using spot analysis methods. The cumulative score across all charts and relevant questions produces a total that falls into NDI, DI, or Inconclusive ranges.

The APA's 2011 meta-analysis reviewed 38 studies involving 3,723 examinations scored by 295 scorers. Event-specific single-issue diagnostic testing produced an aggregated decision accuracy of 89% with a confidence interval of 83%-95% [1]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms aggregated decision accuracy of 89% for single-issue diagnostic testing and 87% across all validated techniques in 38 studies involving 3,723 examinations. The combination of all validated PDD techniques produced an overall decision accuracy of 87% with a confidence interval of 80%-94% [1]Verified Meta-Analytic Survey of Criterion Accuracy of Validated Polygraph Techniques
Confirms aggregated decision accuracy of 89% for single-issue diagnostic testing and 87% across all validated techniques in 38 studies involving 3,723 examinations. These findings provide a strong empirical foundation for the numerical scoring that underlies every diagnostic impression.

Artifact and Anomaly Assessment

Before rendering a diagnostic impression, the examiner reviews the charts for artifacts — physiological anomalies caused by movement, coughing, sneezing, deep sighs, or other non-deception-related factors. If artifacts contaminate a significant portion of the data, the examiner may need to collect additional charts, adjust scoring, or render an Inconclusive result. The OSS-3 algorithm includes the ability to mark artifacted segments that should not be included in the statistical analysis, providing a more objective approach to handling compromised data [5]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Confirms OSS-3 accuracy exceeded average decision accuracy of human scorers on six dimensions, and reports Fleiss' kappa inter-rater reliability of.59 for human scorers.

Behavioral Observation Integration

While the numerical score forms the primary basis for the diagnostic impression, the examiner also documents behavioral observations from the pre-test, in-test, and post-test phases. Research on impression management strategies has shown that deceivers and honest reporters employ different behavioral patterns during investigative interviews [10]Verified The Empirical Basis for the Use of Directed Lie Comparison Questions in Diagnostic and Screening Polygraphs
Confirms little meaningful difference in detection accuracy between directed lie and probable lie comparison questions, supporting the scientific validity of DLCQs. These observations may include the examinee's demeanor, verbal responses, spontaneous statements, and overall cooperation level. Behavioral observations alone are never sufficient to change a diagnostic impression, but they provide important context. The examiner's role requires careful integration of multiple data streams — understanding the role of the polygraph examiner helps clarify how this synthesis occurs.

Final Professional Determination

The examiner weighs all factors — numerical score, chart quality, artifact analysis, testing conditions, examinee suitability, and procedural compliance — to render the diagnostic impression. This process is sometimes referred to as global evaluation, which goes beyond pure numerical analysis to incorporate the full examination context.

In well-conducted examinations using APA-validated techniques, the diagnostic impression should be reproducible by another qualified examiner reviewing the same data. This expectation of reproducibility is a cornerstone of scientific quality in polygraph testing. Research using the OSS-3 algorithm demonstrated that computer algorithms can meet or exceed human experts in polygraph decision making, providing a valuable cross-check on examiner conclusions [5]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Confirms OSS-3 accuracy exceeded average decision accuracy of human scorers on six dimensions, and reports Fleiss' kappa inter-rater reliability of.59 for human scorers.

Approved Professional Language

The specific language used in a diagnostic impression is carefully chosen and carries precise professional meaning. Examiners are trained to use the following standardized terms:

No Deception Indicated (NDI) — The data does not support a conclusion of deception. Deception Indicated (DI) — The data supports a conclusion consistent with deception. Inconclusive — The data does not permit a definitive determination. No Significant Response (NSR) — Used in some federal contexts, equivalent to NDI. Significant Response (SR) — Used in some federal contexts, equivalent to DI. No Opinion — The examination could not be completed or the data was compromised.

Language Examiners Must Avoid

Examiners should not say: "The examinee lied" or "The examinee told the truth" — These are absolute statements that go beyond what physiological data can prove. "Passed" or "Failed" — While commonly used in casual conversation, these terms imply a binary determination that oversimplifies the science. "Guilty" or "Innocent" — These are legal determinations made by courts, not polygraph examiners. "The polygraph proves..." — The polygraph is an assessment tool, not a proof mechanism.

The careful use of qualified language reflects scientific honesty about what the technology can determine. A polygraph measures physiological responses that correlate with deception. The diagnostic impression states whether those correlations were present, absent, or unclear. Some examiners include a narrative qualifier such as: "Based on the physiological data collected during this examination using the Utah Zone Comparison Test, it is the opinion of this examiner that the responses to the relevant questions are No Deception Indicated." This format explicitly states the technique used, the basis for the conclusion, and the professional nature of the determination.

Standard Report Structure

A properly prepared polygraph examination report follows a structured format that places the diagnostic impression in a specific context. A comprehensive report typically includes the following sections:

Cover Page / Header — Identifying information: examinee name, date, case number, requesting party, examiner credentials. Purpose of Examination — A clear statement of why the test was conducted and what issues were addressed. Background Information — Relevant case history, including how the examinee was referred. Pre-Test Interview Summary — Key disclosures, the examinee's understanding of the process, informed consent documentation. Examination Methodology — The specific technique used (e.g., Utah ZCT, Federal ZCT, DLST), the number of charts collected, and the scoring method applied. Research has shown little meaningful difference in detection accuracy between directed lie and probable lie comparison questions, supporting the scientific validity of multiple validated approaches [11]Verified ASTM E2062-11(2017) Standard Guide for PDD Examination Standards of Practice
Confirms this ASTM International standard establishes essential and recommended elements in procedures for PDD examinations. Test Questions — The exact wording of all relevant, comparison, and irrelevant questions. Numerical Scoring Results — The raw scores for each question across each chart presentation, plus any automated algorithm output. Behavioral Observations — Documented observations of the examinee's demeanor and cooperation. Diagnostic Impression / Opinion — The examiner's professional conclusion: NDI, DI, or Inconclusive, with supporting rationale. Examiner Certification — The examiner's signature, license number (where applicable), professional affiliations, and statement of adherence to professional standards.

Why Report Completeness Matters

The diagnostic impression typically appears near the end of the report because it represents the culmination of everything that preceded it. It is the section most readers turn to first, but its meaning is only fully understood in the context of the methodology, scoring, and observations that support it.

Reports that contain only a diagnostic impression without supporting methodology and scoring data should be viewed with skepticism. A properly prepared report must include sufficient detail for another qualified examiner to review the work and reach an independent conclusion. The ASTM International standard E2062 — Standard Guide for PDD Examination Standards of Practice — establishes essential and recommended elements in the procedures for conducting a PDD examination [12]Verified Psycho-legal scholars report positive attitudes towards polygraph validity
Confirms psycho-legal scholars reported positive attitudes toward polygraph validity, supporting acceptance in the most legally relevant scientific community. Working with qualified examiners who follow these standards is essential for producing defensible reports.

Admissibility Standards Across Jurisdictions

The legal treatment of polygraph diagnostic impressions varies dramatically depending on jurisdiction, case type, and procedural context. There is no single rule governing how courts handle this evidence across the United States or internationally.

Some jurisdictions allow polygraph results under stipulation — meaning both parties agree in advance to admit the results. Under the Daubert standard, courts evaluate whether the polygraph methodology meets criteria for scientific reliability, scrutinizing the diagnostic impression for its methodological foundation. Under the Frye standard, courts ask whether the underlying technique has gained general acceptance in the relevant scientific community. Psycho-legal scholars have reported positive attitudes toward polygraph validity, suggesting that the scientific community most relevant to legal proceedings views polygraph testing favorably [13]Verified United States v. Scheffer, 523 U.S. 303 (1998)
Confirms Supreme Court upheld Military Rule of Evidence 707 banning polygraph evidence in court-martial proceedings, while noting some federal appellate courts have abandoned per se exclusion rules.

In United States v. Scheffer (1998), the Supreme Court upheld Military Rule of Evidence 707, which makes polygraph evidence inadmissible in court-martial proceedings [14]Verified Chapter 3: Polygraph for Sex Offender Management (Probation and Supervised Release Conditions)
Confirms federal judiciary procedures for PCSOT including statutory authority, sample condition language, and that polygraph results may not be used as sole basis to revoke supervision. The Court ruled that this per se exclusion does not unconstitutionally abridge the right of accused members of the military to present a defense [14]Verified Chapter 3: Polygraph for Sex Offender Management (Probation and Supervised Release Conditions)
Confirms federal judiciary procedures for PCSOT including statutory authority, sample condition language, and that polygraph results may not be used as sole basis to revoke supervision. Importantly, Scheffer specifically addressed a military rule and did not create a universal federal exclusion — federal courts outside the military context handle polygraph admissibility on a case-by-case basis, with many applying Daubert analysis [14]Verified Chapter 3: Polygraph for Sex Offender Management (Probation and Supervised Release Conditions)
Confirms federal judiciary procedures for PCSOT including statutory authority, sample condition language, and that polygraph results may not be used as sole basis to revoke supervision. The Supreme Court itself acknowledged in Scheffer that "some Federal Courts of Appeal have abandoned the per se rule excluding polygraph evidence" [14]Verified Chapter 3: Polygraph for Sex Offender Management (Probation and Supervised Release Conditions)
Confirms federal judiciary procedures for PCSOT including statutory authority, sample condition language, and that polygraph results may not be used as sole basis to revoke supervision. For a comparison of international approaches, see our guide on R. v. Béland, the Canadian case addressing polygraph admissibility.

Different Legal Contexts

Criminal defense: Defense attorneys may use an NDI result to support plea negotiations, argue for reduced charges, or petition for case dismissal. A DI result obtained during a defense-initiated polygraph is typically protected by attorney-client privilege and never disclosed.

Prosecution: Prosecutors may reference polygraph results in plea negotiations, particularly in sex offense cases where PCSOT results are part of supervision.

Family court: Some family courts consider polygraph evidence in custody disputes, particularly where allegations of abuse are at issue. The diagnostic impression may be admitted as one piece of a broader evidentiary picture.

Sentencing and probation: Even in jurisdictions that exclude polygraph evidence at trial, diagnostic impressions from PCSOT examinations are frequently used in sentencing recommendations, probation modification hearings, and treatment compliance evaluations. Under 18 U.S.C. § 3563, courts may order defendants to submit to periodic polygraph testing as a condition of supervised release [15]Verified Employee Polygraph Protection Act of 1988 (29 U.S.C. Chapter 22)
Confirms EPPA prohibits most private employers from using lie detector tests, with exemptions for government agencies, security firms, and pharmaceutical companies, effective December 27, 1988.

Judges evaluating polygraph diagnostic impressions typically focus on whether the examiner used a validated technique, whether the examination was conducted according to professional standards, whether the data supports the stated conclusion, and whether the examiner's qualifications are sufficient to render the opinion. The issue of false confessions sometimes intersects with polygraph evidence in criminal proceedings.

EPPA Framework

In the private sector, polygraph use is heavily regulated by the Employee Polygraph Protection Act of 1988 (EPPA). Effective December 27, 1988, EPPA prohibits most private employers from using lie detector tests for pre-employment screening or during the course of employment [16]Verified EPPA Guidelines - American Polygraph Association
Confirms EPPA procedural requirements including 48-hour advance notice, 3-year record retention by employers, and $10,000 penalty per violation. Federal, state, and local government employers are exempted from the Act [16]Verified EPPA Guidelines - American Polygraph Association
Confirms EPPA procedural requirements including 48-hour advance notice, 3-year record retention by employers, and $10,000 penalty per violation. Limited exceptions exist for security service firms (armored car, alarm, and guard companies), pharmaceutical manufacturers and distributors, and employers with reasonable suspicion of employee involvement in workplace incidents resulting in economic loss [16]Verified EPPA Guidelines - American Polygraph Association
Confirms EPPA procedural requirements including 48-hour advance notice, 3-year record retention by employers, and $10,000 penalty per violation.

Where polygraph testing is permitted under EPPA, employers receive the opinion letter rather than the full examination report. The diagnostic impression informs their decision-making but cannot serve as the sole basis for adverse employment action — additional supporting evidence is always required [16]Verified EPPA Guidelines - American Polygraph Association
Confirms EPPA procedural requirements including 48-hour advance notice, 3-year record retention by employers, and $10,000 penalty per violation. Employers must also provide 48 hours advance notice before the scheduled test and retain documentation for at least three years [17]Verified Post-conviction polygraph testing of sex offenders
Confirms PCSOT is common in the US and increasingly applied in England and Wales for sex offender supervision and treatment. Violations carry civil penalties of up to $10,000 per violation [16]Verified EPPA Guidelines - American Polygraph Association
Confirms EPPA procedural requirements including 48-hour advance notice, 3-year record retention by employers, and $10,000 penalty per violation.

Employer Best Practices

HR professionals receiving polygraph diagnostic impressions should understand that an NDI result is strong evidence supporting the employee's account, while a DI result warrants further investigation rather than automatic disciplinary action. An Inconclusive result means the test was unable to provide a definitive answer — it should not be treated as evidence of deception.

Employers should verify that the examiner used a validated technique that meets APA standards, that the examination was properly documented, and that the examiner holds appropriate state licensure where required. Many states have their own polygraph licensing requirements that may impose additional standards beyond federal law.

PCSOT Applications

In post-conviction sex offender testing (PCSOT), the diagnostic impression takes on particular significance within the treatment and supervision framework. PCSOT is common in the United States and increasingly applied in England and Wales [18]Verified Research Overview: Post Conviction Sex Offender Polygraph Testing
Confirms PCSOT examination types (sexual history disclosure, instant offense disclosure, maintenance/monitoring) and their distinct purposes in sex offender management. The polygraph examination is used to assist in identifying specific risks and targeting treatment interventions, and to increase disclosure of activities during the supervision period [15]Verified Employee Polygraph Protection Act of 1988 (29 U.S.C. Chapter 22)
Confirms EPPA prohibits most private employers from using lie detector tests, with exemptions for government agencies, security firms, and pharmaceutical companies, effective December 27, 1988.

PCSOT examinations take three basic forms: sexual history disclosure, instant offense disclosure, and maintenance/monitoring examinations [19]Verified Why polygraph testing does not consistently lead to reduced recidivism for individuals convicted of sexual offending
Confirms that systematic review by Elliott and Vollm (2018) found 19 studies established PCSOT elicits significant increase in disclosures compared to non-polygraphed participants. Each type generates a diagnostic impression that treatment providers and probation officers use to guide supervision decisions.

Research consistently supports the polygraph as a truth facilitator in PCSOT contexts. A systematic review by Elliott and Vollm (2018) found that across 19 studies from the US, UK, and Netherlands, PCSOT elicits a significant increase in disclosures relevant to supervision compared to non-polygraphed participants [20]Verified Post-Conviction Sex Offender Polygraph Examination: Client-Reported Perceptions of Utility and Accuracy
Confirms majority of surveyed sex offenders reported polygraph motivated them to be more honest in treatment and supervision, acknowledging its utility. The Kokish, Levenson, and Blasingame (2005) study surveyed sex offenders about their polygraph experiences and found the majority reported polygraph motivated them to be more honest in treatment and supervision [21]Verified The Use of Polygraph in Sex Offender Treatment
Confirms polygraph assists treatment providers in identifying specific risks and needs, and that polygraph is one component among many in offender treatment, not to be used in isolation.

Under approved federal judiciary procedures, polygraph results may be used to increase the level of supervision, modify treatment plans, or generate a separate investigation — but a polygraph result may not be used as the sole basis to revoke supervision [15]Verified Employee Polygraph Protection Act of 1988 (29 U.S.C. Chapter 22)
Confirms EPPA prohibits most private employers from using lie detector tests, with exemptions for government agencies, security firms, and pharmaceutical companies, effective December 27, 1988.

Treatment Integration

Treatment providers use the diagnostic impression to evaluate client engagement and truthfulness. An NDI result on a maintenance polygraph supports the conclusion that the offender is complying with treatment conditions. A DI result may indicate non-compliance, necessitating adjustments to the treatment plan or increased supervision. An Inconclusive result may warrant additional testing.

Polygraph-assisted therapy in the PCSOT context has been shown to yield greater disclosure of offense history, contributing to more accurate risk assessment [19]Verified Why polygraph testing does not consistently lead to reduced recidivism for individuals convicted of sexual offending
Confirms that systematic review by Elliott and Vollm (2018) found 19 studies established PCSOT elicits significant increase in disclosures compared to non-polygraphed participants. The polygraph examination assists treatment providers in identifying specific risks and needs of each individual offender [22]Verified APA-Accredited Polygraph Training Program Requirements
Confirms APA-accredited programs require minimum 400 hours of in-residence study completed in 10 to 17 weeks with at least 95% instruction by recognized faculty. However, it is important to note that polygraph is one form of behavioral monitoring among many, and results should not be used in isolation [22]Verified APA-Accredited Polygraph Training Program Requirements
Confirms APA-accredited programs require minimum 400 hours of in-residence study completed in 10 to 17 weeks with at least 95% instruction by recognized faculty.

APA Professional Standards

The American Polygraph Association sets strict standards governing how examiners document and support their diagnostic impressions. The APA Standards of Practice, most recently amended August 23, 2024, require that examinations be conducted using validated techniques supported by research conducted in accordance with APA research standards [9]Verified Impression management strategies of deceivers and honest reporters in an investigative interview
Foundational research on behavioral differences between deceptive and truthful individuals relevant to examiner behavioral observations during polygraph testing. Where examiners deviate from the protocols of a validated technique, the deviations must be explained in writing [9]Verified Impression management strategies of deceivers and honest reporters in an investigative interview
Foundational research on behavioral differences between deceptive and truthful individuals relevant to examiner behavioral observations during polygraph testing.

Examiner qualification requirements include graduation from an APA-accredited polygraph training program requiring a minimum of 400 hours of in-residence study completed in 10 to 17 weeks [23]Verified Policy for APA Continuing Education Hours
Confirms practicing examiners must complete minimum 30 continuing education hours every two years in coursework related to polygraphy. At least 95 percent of instruction must be delivered by recognized faculty members [23]Verified Policy for APA Continuing Education Hours
Confirms practicing examiners must complete minimum 30 continuing education hours every two years in coursework related to polygraphy. The APA requires practicing examiners to complete a minimum of 30 continuing education hours every two years in coursework related to the field of polygraphy [24]Verified APA Model Policy for Paired Testing - Data Retention
Confirms APA recommends retaining all relevant data for minimum five years and that records should not be destroyed prior to resolution of legal proceedings. Practicing examiners are responsible for maintaining their own records documenting compliance with this requirement [24]Verified APA Model Policy for Paired Testing - Data Retention
Confirms APA recommends retaining all relevant data for minimum five years and that records should not be destroyed prior to resolution of legal proceedings.

Regarding record retention, APA Standards of Practice require that audio or audio-video recordings of all phases of the exam be maintained for a minimum of one year [9]Verified Impression management strategies of deceivers and honest reporters in an investigative interview
Foundational research on behavioral differences between deceptive and truthful individuals relevant to examiner behavioral observations during polygraph testing. The APA's model policy for paired testing recommends retaining all relevant data for a minimum of five years, and records should never be destroyed prior to the resolution of any legal proceedings in which the polygraph data might be at issue [25]Verified The Polygraph and Lie Detection
Foundational review of polygraph science by the National Research Council establishing the evidence base for polygraph accuracy and methodology.

Inter-Rater Reliability

Inter-rater reliability — the extent to which different examiners reviewing the same data reach the same conclusion — is a critical quality measure for polygraph testing. Amsel (2013) found that inter-rater reliability among polygraph examiners (.77) was comparable to that of psychologists (.79) and exceeded that of physicians (.55) [7]Verified Comparative Review of Polygraph and Other Diagnostic Tools and Methods
Confirms polygraph diagnostic accuracy (.88) comparable to medical imaging technologies and inter-rater reliability among examiners (.77) exceeded physicians (.55) and approached psychologists (.79). This finding is notable because it demonstrates that polygraph examiners achieve reliability levels consistent with other established diagnostic professions.

The development of automated scoring algorithms has further strengthened reliability. The OSS-3 algorithm, in a Monte Carlo comparison study, demonstrated accuracy that exceeded the average decision accuracy of 10 human scorers on six dimensions of accuracy [5]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Confirms OSS-3 accuracy exceeded average decision accuracy of human scorers on six dimensions, and reports Fleiss' kappa inter-rater reliability of.59 for human scorers. Computer algorithms provide perfect reliability — the same input always produces the same output — offering a valuable benchmark against which human scoring can be compared. Interrater reliability for human scorers in that study was measured at Fleiss' kappa of.59 [5]Verified Brute-Force Comparison: A Monte Carlo Study of the Objective Scoring System version 3 (OSS-3) and Human Polygraph Scorers
Confirms OSS-3 accuracy exceeded average decision accuracy of human scorers on six dimensions, and reports Fleiss' kappa inter-rater reliability of.59 for human scorers, consistent with previously reported reliability estimates. The integration of AI in polygraph systems continues to advance the objectivity and consistency of diagnostic impressions.

What the Diagnostic Impression Cannot Do

The diagnostic impression cannot determine absolute truth or deception with certainty. It represents a professional opinion based on physiological data that correlates with deception. The psychophysiological basis of the CQT rests on the comparison of physiological responses to different types of questions — it does not directly read thoughts or intentions.

A diagnostic impression cannot determine the reasons behind physiological responses. A person may show reactions consistent with deception due to anxiety, fear, or emotional distress unrelated to actual deception. Conversely, certain individuals may not produce detectable physiological changes even when being deceptive. Understanding the signs of deception helps contextualize what polygraph data can and cannot reveal.

The diagnostic impression applies only to the specific questions asked during the examination. An NDI result on a particular set of questions does not mean the examinee was truthful about everything — only about the topics covered by the relevant questions.

Common Misunderstandings

Inconclusive means the examiner suspects deception — This is false. Inconclusive means the data did not support either conclusion with sufficient clarity. There are many legitimate reasons for inconclusive outcomes unrelated to deception.

A DI result means the person is guilty — This is false. A DI result means the physiological data is consistent with deception. It is not a legal finding of guilt or a definitive statement of dishonesty.

A second examiner would always reach the same conclusion — While inter-rater reliability is strong when standardized techniques and scoring methods are used, variability exists. Amsel's research showed polygraph inter-rater reliability at.77, which is good but not perfect [7]Verified Comparative Review of Polygraph and Other Diagnostic Tools and Methods
Confirms polygraph diagnostic accuracy (.88) comparable to medical imaging technologies and inter-rater reliability among examiners (.77) exceeded physicians (.55) and approached psychologists (.79). Using validated automated algorithms like OSS-3 alongside manual scoring provides an additional layer of objectivity.

Polygraph results are either admissible or inadmissible — The reality is far more nuanced. Admissibility varies by jurisdiction, case type, and the specific procedural context. Even where trial admissibility is restricted, diagnostic impressions are frequently used in plea negotiations, sentencing, probation, and treatment contexts. Polygraph examination disqualification can also affect how results are interpreted.