The credibility assessment examination using a polygraph involves a structured and meticulous process designed to ensure the accuracy and integrity of the examination, as well as the fair and ethical treatment of the examinee.

The polygraph test, commonly known as a lie detector test, is a method used to measure and record several physiological indicators such as blood pressure, pulse, respiration, and skin conductivity while a person is asked and answers a series of questions. The premise behind the test is that deceptive answers will produce physiological responses that can be differentiated from those associated with non-deceptive answers. Here’s a detailed description of the polygraph test:

Here’s an overview of the process:

  1. Test Sponsor’s Need to Know the Truth

The process begins with the entity requiring the test (the test sponsor) recognizing a need to ascertain the truth regarding specific statements or allegations. This need can arise in various contexts, such as criminal investigations, employment verifications, or security clearances.

  1. Examiner’s Information Needs

The polygraph examiner, a professional trained in conducting polygraph tests, gathers essential background information about the case and the subject. This information helps in planning the test, including formulating the questions and understanding the context of the examination.

  1. Contact Between Examiner and Subject

Initial contact with the subject involves explaining the purpose of the polygraph test, the process involved, and addressing any concerns or questions the subject might have. This step is crucial for ensuring the subject’s informed consent and cooperation.

  1. Informed Consent

Obtaining informed consent from the subject is mandatory before proceeding with the test. This ensures that the subject agrees to participate willingly and is fully aware of the implications and the nature of the polygraph examination.

  1. Ideal Environmental Conditions

The polygraph test is conducted in an environment designed to minimize distractions and discomfort. This includes controlling factors like temperature, noise, and seating arrangements to ensure the subject remains focused and the test results are accurate.

  1. Pre-test Interview

A comprehensive interview is conducted before the actual polygraph test. This interview serves to build rapport, clarify the examination process, discuss the case under investigation, and inform the subject about the implications of their responses. It also helps in tailoring the polygraph questions to the specifics of the case.

  1. Configuration of the Polygraph Test Questionnaire

Based on the pre-test interview and the case details, the examiner formulates a set of questions that are precise, relevant, and designed to elicit clear physiological responses indicative of truthfulness or deception.

Questions are formulated based on the specifics of the investigation or the information being sought. These typically include relevant questions (directly related to the matter at hand), control questions (related to general honesty), and irrelevant questions (neutral in nature).

  1. Choice of the Appropriate Technique

The examiner selects the most suitable polygraph technique based on the specific objectives of the test and the nature of the information being sought. Different methodologies can be employed to optimize the examination’s effectiveness.

Basic Components

Sensors and Monitors: Attached to the examinee to measure physiological responses. These include blood pressure cuffs, chest straps for respiration, and galvanic skin response sensors.

Polygraph Machine: Records the physiological data from the sensors. Modern polygraphs are computerized, offering more sophisticated analysis of the data.

  1. Use of an Intelligent Polygraph

Modern polygraph examinations may utilize advanced, “intelligent” polygraph systems equipped with sophisticated algorithms and sensors. These devices measure various physiological indicators, such as heart rate, blood pressure, respiration, and skin conductivity, to assess the subject’s responses more accurately.

  1. Testing Phase:

The polygraph test involves asking the prepared questions while monitoring the subject’s physiological responses. These responses are then analyzed to determine the credibility of the subject in relation to the questions posed.

The examinee is asked the prepared questions in a controlled environment to ensure that the physiological responses are solely in reaction to the questions.

Types of Questions

Relevant Questions: Directly related to the issue being investigated.

Control Questions: Designed to elicit a response based on known truths, allowing the examiner to establish a baseline for truthful responses.

Irrelevant Questions: Unrelated to the issue and expected to produce a neutral physiological response.


Several techniques are used in polygraph testing, including the Comparison Question Test (CQT), the Guilty Knowledge Test (GKT), and others, each with its own methodology for questioning and analysis.

Data Collection: The polygraph records the examinee’s physiological responses to each question, capturing any deviations from the baseline established during the pre-test phase.

Post-test Phase: Analyzing Results

Data Analysis: The examiner analyzes the physiological responses to differentiate between truthful and deceptive answers. This involves comparing responses to relevant questions with responses to control and irrelevant questions.

Results Interpretation: Based on the analysis, the examiner determines whether the responses suggest truthfulness, deception, or inconclusiveness.

  1. Issuance of the Report

Following the examination, the examiner compiles a report detailing the findings, including an analysis of the subject’s physiological responses and any conclusions drawn from the test. This report is then provided to the test sponsor, often with recommendations based on the results.

This process underscores the importance of procedural guarantees, such as informed consent and the ethical treatment of the examinee, while striving to ensure the examination’s accuracy and reliability.