Table of Contents
Introduction
Polygraph examinations often culminate in a “diagnostic opinion” or “screening opinion,” terms that convey the examiner’s professional judgment regarding the examinee’s truthfulness or knowledge of specific information. These opinions are vital to interpreting polygraph results accurately and responsibly, providing clear, standardized conclusions for clients, investigators, and legal professionals. The American Polygraph Association (APA) has established specific guidelines for these terms, ensuring they are used consistently and meaningfully. This article explains the APA’s standards for diagnostic opinions, explores the various result categories, and highlights their implications in different polygraph contexts.
1. Understanding Diagnostic Opinions in Polygraph Examinations
What is a Diagnostic Opinion?
A diagnostic opinion is a professional conclusion based on the physiological data collected during a polygraph examination, interpreted in the context of the examinee’s responses to relevant questions. Diagnostic opinions are typically used in evidentiary or investigative examinations, where the examiner’s judgment directly addresses an individual’s involvement in, or knowledge of, a specific incident.
Key Components of Diagnostic Opinions
The APA’s guidelines for diagnostic opinions emphasize that they should be based on validated polygraph techniques with proven accuracy. This includes following standardized decision rules and ensuring that physiological responses to relevant, comparison, and neutral questions are accurately scored and analyzed. By adhering to these standards, examiners produce diagnostic opinions that are credible, consistent, and scientifically grounded.
2. Common Diagnostic Opinion Terminology
Deception Indicated (DI)
A “Deception Indicated” result suggests that the physiological data indicates the examinee may have been deceptive in response to the relevant questions. In practical terms, DI means that the examiner has observed a pattern of physiological responses—such as increased heart rate, electrodermal activity, or irregular breathing—that aligns with deception.
No Deception Indicated (NDI)
The “No Deception Indicated” outcome means that the examinee’s physiological responses do not suggest deception regarding the relevant questions. In this case, the examiner’s analysis supports a conclusion that the examinee was truthful, with consistent physiological responses that do not raise suspicion of deceptive behavior.
Inconclusive (INC)
An “Inconclusive” result occurs when the physiological data does not lead to a clear conclusion. This can happen for various reasons, such as examinee anxiety, external disturbances, or inconsistent data. Inconclusive results do not suggest either truthfulness or deception; rather, they indicate that further investigation or testing may be necessary.
No Opinion (NO)
A “No Opinion” result is issued when external factors or technical issues prevent the examiner from forming a valid opinion based on the available data. For example, if there is a sudden equipment failure or the examinee is unable to complete the test, a “No Opinion” outcome may be appropriate. This result upholds integrity by acknowledging that a reliable diagnostic opinion cannot be reached under the circumstances.
3. The Role of Diagnostic Opinions in Evidentiary Examinations
Evidentiary Use of Diagnostic Opinions
In legal contexts, diagnostic opinions may serve as evidence when polygraph results are admitted in court. These opinions provide clear statements regarding an individual’s potential involvement in or knowledge of specific events, supporting legal professionals in making informed decisions. Because of their potential impact, evidentiary diagnostic opinions must meet the highest accuracy standards, with validated polygraph techniques that achieve a minimum accuracy rate of 90%.
Implications for Legal Proceedings
A diagnostic opinion in an evidentiary examination can significantly influence the outcome of a legal case. However, the APA advises examiners to communicate the probabilistic nature of polygraph results, including margins of uncertainty, to provide an accurate context for their conclusions. This transparency helps legal professionals interpret polygraph findings responsibly, using them as one of several factors in the case.
4. Diagnostic Opinions in Investigative Examinations
Assisting Investigative Efforts
Diagnostic opinions are frequently used in investigative examinations, where the goal is to gather information to aid ongoing investigations. In this context, diagnostic opinions help investigators identify potential leads, evaluate suspects, or corroborate witness statements. While these results are not generally admissible in court, they offer valuable insights that support investigative decision-making.
Accuracy Standards for Investigative Examinations
APA standards require that diagnostic opinions in investigative contexts reach an accuracy level of 80% or higher. Although this threshold is slightly lower than that required for evidentiary examinations, it ensures that investigative polygraph results remain reliable while allowing for some flexibility in exploratory situations.
5. Distinctions Between Diagnostic and Screening Opinions
Diagnostic vs. Screening Opinions
A diagnostic opinion is specific to event-related examinations, where the examinee’s involvement or knowledge regarding a particular incident is in question. In contrast, a screening opinion is typically used in routine screenings, such as pre-employment assessments, where no specific incident or allegation is being investigated.
Screening Opinion Terminology
Screening opinions often use terms like “Significant Response” (SR) or “No Significant Response” (NSR) rather than “Deception Indicated” or “No Deception Indicated.” This terminology reflects the lower-stakes, preventive nature of screening examinations and emphasizes that results are indicative of general trustworthiness rather than event-specific deception.
Implications for Polygraph Examiners
Understanding the differences between diagnostic and screening opinions is essential for polygraph examiners, as each type serves a distinct purpose and requires a unique approach. Diagnostic opinions are more narrowly focused and require higher accuracy, while screening opinions prioritize probabilistic results that exceed random chance.
6. How Diagnostic Opinions Support Quality Control and Accountability
Documenting the Diagnostic Process
APA standards require examiners to document their analysis methods, including physiological response scoring, decision rules, and any other factors that contributed to the diagnostic opinion. This documentation is vital for quality control, as it enables peer reviewers or oversight bodies to replicate the analysis and verify that the diagnostic opinion aligns with APA-approved standards.
Maintaining Accountability in Results
Detailed documentation of diagnostic opinions supports examiner accountability, providing a clear record of how each conclusion was reached. This transparency is essential when results are scrutinized, particularly in legal or high-stakes investigative contexts, where examiners may be required to justify their conclusions based on specific data points and scoring criteria.
7. Reporting Probabilistic Margins in Diagnostic Opinions
Importance of Probabilistic Margins
The APA encourages examiners to report probabilistic margins of uncertainty in their diagnostic opinions. This means acknowledging the likelihood of error or inconclusiveness, which provides an honest, transparent view of the reliability of the findings. Reporting these margins helps stakeholders interpret polygraph results responsibly, particularly in high-stakes cases where the diagnostic opinion may influence significant decisions.
Applications in High-Stakes Examinations
In legal cases or sensitive investigations, reporting probabilistic margins adds context to diagnostic opinions. For example, a diagnostic opinion of “Deception Indicated” may be accompanied by a probabilistic margin indicating the statistical confidence in the result. This additional information enables clients, investigators, and legal professionals to make more informed, nuanced decisions based on polygraph findings.
Conclusion
Diagnostic opinions play a critical role in polygraph examinations, offering clear, standardized conclusions regarding an examinee’s truthfulness or knowledge. By adhering to the APA’s guidelines for diagnostic opinions, examiners ensure their findings are scientifically reliable, ethically transparent, and professionally accountable. Whether used in legal, investigative, or screening contexts, diagnostic opinions provide stakeholders with valuable insights that support responsible decision-making. Through careful analysis, accurate terminology, and transparency in reporting, polygraph examiners maintain the integrity of their practice and reinforce trust in the polygraph profession.
