Table of Contents
Overview of Directed Lie Screening Test (DLST)
The Directed Lie Screening Test (DLST) is a sophisticated method utilized primarily in polygraph examinations for various groups such as applicants, sex offenders, and security clearance candidates. Developed to overcome the challenges associated with Probable Lie Comparison (PLC) questions, DLST capitalizes on the benefits of Control Question Tests (CQT) while minimizing their drawbacks, such as intrusiveness and lack of standardization.
DLST Composition and Structure
The DLST is structured to ensure high sensitivity to deception while maintaining a simplified and standardized approach. Typically, a DLST consists of:
- Two neutral questions
- Two relevant questions
- Two directed lie comparison questions
- One sacrifice relevant question
This configuration is administered in a single chart per test, with an option to conduct up to three separate tests per examinee in a single session, providing a comprehensive assessment framework.
Procedure for Administering DLST
The administration of DLST involves several critical steps to ensure the integrity and effectiveness of the test:
- Building rapport with the examinee
- Verifying the identity of the examinee
- Explaining the test procedure and sensors
- Securing consent and completing necessary waiver forms
- Conducting an in-depth background interview
- Providing explanations of physiology and the test questions
- Carrying out the actual test followed by a detailed data analysis
- Conducting a post-test interview to discuss the results and clarify any ambiguities
Each step is crucial to maintaining the procedural integrity and reliability of the DLST, ensuring that the test results are both valid and legally defensible.
Scoring and Evaluation
DLST utilizes a detailed scoring system to evaluate the responses of the examinee. Questions are spaced 20 to 30 seconds apart to allow physiological responses to return to baseline. The scoring involves a comparative analysis of the responses to directed lies and relevant questions. Notably, DLST can be scored using validated techniques such as the Empirical Scoring System (ESS) or the NCCA Scoring System 7-position.
Challenges and Artifacts
Handling artifacts—unintended or irregular physiological responses—is a critical aspect of DLST. If artifacts affect the evaluation of a relevant question, the examiner may choose to add a fourth set of questions or conduct a short test to ensure accurate results. The first three non-artifacted presentations of any relevant question are scored, maintaining the integrity of the test evaluation.
Benefits of DLST
DLST offers multiple advantages over traditional polygraph techniques:
- High Sensitivity and Specificity: DLST is highly sensitive to deception, providing reliable results while also overcoming the specificity issues often seen in other interrogation techniques.
- Standardization: The standardized approach reduces examiner bias and increases the reproducibility of test results across different scenarios.
- Minimized Intrusiveness: By avoiding overly intrusive probable lie comparisons, DLST respects the dignity of the examinee while still effectively assessing truthfulness.
Conclusion
The Directed Lie Screening Test represents a significant advancement in polygraph testing technology. By integrating directed lies in a controlled, standardized format, DLST enhances the accuracy and reliability of polygraph examinations, making it a valuable tool for law enforcement, security clearance assessments, and other sensitive areas where truth verification is paramount.
