The Directed Lie Screening Test (DLST) is a psychological evaluation method used primarily in the context of security screening and lie detection. This technique involves instructing the testee to deliberately lie in response to specific controlled questions. These directed lies create physiological and psychological benchmarks which can then be compared against responses given to questions of interest, potentially indicating deception. Here’s a step-by-step guide on how to effectively use the DLST:

Step 1: Preparation

Before administering the DLST, it is essential to prepare properly:

  • Understand the Purpose: Clearly define what you are trying to detect or verify in the individual’s responses.
  • Environment Setup: Ensure the testing environment is controlled and free from distractions to maintain the testee’s focus.
  • Consent and Briefing: Obtain informed consent from the participant, explaining the nature of the test, the types of questions to be asked, and the use of their data.

Step 2: Baseline Measurement

Start with a baseline measurement to understand the normal physiological responses of the testee:

  • Calm Conversation: Engage in a neutral discussion to measure the normal stress levels and physiological responses of the testee.
  • Control Questions: Ask simple, non-threatening questions to establish how the testee responds when there is no pressure to deceive.

Step 3: Directed Lie Questions

Introduce the directed lies:

  • Simple Instructions: Clearly instruct the testee to lie in response to specific questions. These questions are usually innocuous and straightforward (e.g., “Is today Monday?” when it is actually Tuesday).
  • Repetition: It may be necessary to repeat directed lie questions to establish a consistent physiological response pattern.

Step 4: Relevant Questions

After establishing the baseline and directed lie responses, proceed with the questions of interest:

  • Crafting Questions: Develop questions that are direct and specific to the issue under investigation. Avoid ambiguity to ensure the clarity of the testee’s responses.
  • Question Order: Intersperse relevant questions with neutral ones to modulate the psychological pressure and observe variations in responses.

Step 5: Analysis

Analyze the physiological and psychological responses:

  • Compare Responses: Look for deviations from the baseline and directed lie responses when the testee answers the relevant questions.
  • Use of Equipment: Depending on the setup, use lie detection equipment to measure physiological changes such as heart rate, blood pressure, and skin conductivity.

Step 6: Follow-Up

After the test:

  • Review Results: Analyze the data collected to identify inconsistencies or signs of deception.
  • Further Investigation: Depending on the results, decide whether further detailed questioning or additional tests are necessary.

Step 7: Ethical Considerations

Always consider the ethical implications:

  • Respect Privacy: Ensure the confidentiality and privacy of the information obtained during the test.
  • Accuracy and Limitations: Be aware of the limitations of the DLST and avoid making definitive judgments based solely on this test.


The Directed Lie Screening Test is a valuable tool in security and investigative contexts for assessing truthfulness. However, it should be used with caution and in conjunction with other investigative methods to ensure fairness and accuracy. The effectiveness of DLST depends significantly on the skill and experience of the administrator, as well as the adherence to ethical guidelines.

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