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Polygraph examinations rely on the measurement of physiological responses to assess an individual’s truthfulness. One of the most widely used methods in polygraph testing is the Comparison Test Format (CTF), a structured and validated approach employed for criminal investigations, personnel screenings, and source validation. In this article, we will explore the elements of the Comparison Test Format as outlined in the Federal Psychophysiological Detection of Deception Examiner Handbook and how it plays a critical role in detecting deception.
Overview of Comparison Test Formats (CTF)
The Comparison Test Format encompasses various polygraph techniques, including the widely used Modified General Question Test (MGQT) and the Zone Comparison Test (ZCT). Although the ZCT is considered a separate format due to its unique application, it is still classified under the broader umbrella of comparison testing methods. These formats are commonly used in federal polygraph examinations and have been validated through research and field testing.
Comparison Test Formats are essential for detecting deception in high-stakes situations such as:
- Criminal investigations
- National security screenings
- Personnel vetting for sensitive government positions
The primary objective of the CTF is to evaluate the physiological responses of an examinee when answering relevant and comparison questions. This comparison helps distinguish between truthful and deceptive responses by measuring variations in autonomic nervous system responses, such as changes in heart rate, blood pressure, and respiratory patterns.
Question Structure in CTF
The effectiveness of the Comparison Test Format depends on the careful construction and sequence of test questions. During the pretest phase, the examiner reviews all questions with the examinee to ensure understanding and minimize anxiety unrelated to the test. The key types of questions in the CTF are:
- Relevant Questions: These questions address the specific issue under investigation, such as involvement in a crime or unauthorized actions. For example:
- “Did you steal that car from the parking lot?”
Relevant questions directly assess whether the examinee is involved in the matter under investigation, and any deceptive response is expected to produce a noticeable physiological reaction.
- Comparison Questions: Also known as Probable-Lie Comparison Questions (PLCQs), these questions are designed to elicit a physiological response by asking the examinee about unrelated but similar issues. The purpose is to compare their reactions to relevant questions with their responses to questions that they are more likely to lie about. For instance:
- “Before 1997, did you ever steal anything of value?”
The comparison between the examinee’s response to these questions and the relevant questions is crucial for detecting deception.
- Sacrifice Relevant Questions: This type of question introduces the relevant issue to the examinee without directly addressing the specific matter under investigation. It prepares the examinee for the introduction of the primary relevant questions. For example:
- “Regarding the theft of the car, do you intend to answer each question truthfully?”
- Irrelevant Questions: These questions are neutral and unrelated to the investigation. They help establish a baseline physiological response from the examinee. For instance:
- “Are you now in Alabama?”
Irrelevant questions do not elicit any emotional or psychological reaction and are not scored but are used to assess the normal physiological state of the examinee.
- Directed-Lie Comparison Questions: Directed-Lie Comparison Questions are specialized questions where the examiner instructs the examinee to lie intentionally about a minor issue. These questions are constructed to separate the relevant issue from the comparison category, and the physiological response to lying can be compared to the response to the relevant questions. An example might be:
- “Did you ever lie to a coworker about anything?”
Data Collection and Test Operations
After the pretest phase, the polygraph examiner collects physiological data through a series of charts, typically three to five. The first chart usually begins with an irrelevant question to establish the baseline, followed by a series of relevant and comparison questions.
During the data collection phase, the examiner may rotate the relevant and comparison questions across different charts. This helps avoid any patterns that the examinee may recognize and reduces the possibility of manipulation. At least one chart must include a format where the relevant question with the greatest physiological response is paired with the comparison question that also triggered the greatest response.
The process generally involves:
- Presenting two to five relevant questions
- Presenting two to four comparison questions
- Ensuring that relevant questions are bracketed by comparison questions in at least one chart
Test Data Analysis
Test data analysis in CTF is conducted through a numerical evaluation process, typically using the 3-position or 7-position scoring scales. The examiner assesses the physiological responses from the comparison and relevant questions and assigns scores based on the intensity of the reactions.
The examiner uses spot analysis to evaluate groups of relevant questions and compare them against their corresponding comparison questions. The greatest physiological response in each set is reviewed, allowing the examiner to determine whether deception is indicated.
Opinion Rendering Criteria
At the conclusion of the examination, the examiner renders an opinion based on the following criteria:
- Deception Indicated (DI): To render an opinion of deception, the physiological response to the relevant question must be significantly stronger than the response to the comparison questions. A score of minus three (-3) or lower in any overall vertical spot indicates deception.
- No Deception Indicated (NDI): A non-deceptive conclusion is reached if the physiological response to the comparison questions is greater than the response to the relevant questions. The examinee must score plus three (+3) or higher in each spot to indicate truthfulness.
- No Opinion (NO): If the test data does not provide a clear indication of deception or truthfulness, the examiner may render a “No Opinion” verdict. This outcome is usually reserved for cases where the physiological responses are inconclusive or inconsistent.
Conclusion
The Comparison Test Format remains a critical tool in polygraph testing, providing a structured and scientifically validated method for detecting deception. By analyzing the physiological responses to carefully constructed relevant and comparison questions, examiners can accurately assess an individual’s truthfulness in criminal investigations, personnel screenings, and other high-stakes scenarios. The flexibility of the CTF allows it to be adapted to various contexts, ensuring its continued relevance in federal polygraph examinations
