The thought of undergoing a lie detector test can be terrifying and intimidate most people. Sitting there with wires and tubes attached and wrapped around your body give most people goose bumps. Even with nothing to hide, the sight of the metal box instruments sitting next to you will strike momentary fear into you. How then the lie detector does works and what are the procedures involved in taking polygraph tests?

Procedures involved in a polygraph test.

Mandate: In order for lie detector to be used, the first step is to get the mandate for the polygraph expert approved by the government, law enforcement and security organizations, the legal community, the private sector and private citizens so as to be able to administer the test. It is taken to verify the truthfulness of statements regarding a certain issue.

Information gathering: The polygraph examiner will now hold a meeting with the clients during which he will gather the needed information and facts about the case under investigation. The information and facts provided will form the basis for the polygraph examination. The facts to be used must have been established through thorough investigation.

Pre-test phase:

The examiner will:

  • Inform the examinee about the issue to be investigated.

  • Remind the examiner of constitutional rights, the rights to an attorney and of polygraph test being voluntary.

  • Complete all necessary documentation for the test.

  • Give the examinee a detailed explanation of the instruments to be used and how it works.

  • Answer questions from the examinee and get his version of facts about the issue under investigation.

  • Formulate the questions to be asked during the test.

The next stage is the in-test phase. Before that though, the examiner will have to fasten the components around the examinees the body. The instruments will connect the examinee to the lie detector. The components are specially equipped with sensors that will collect, measure and record information onto the polygraph chart.

The components to be used include:

  • Blood pressure cuff: it is used to obtain a continuous tracing of the examinee’s cardiovascular activities and it is attached to the examinee’s upper arm.

  • Pneumographs: They are used in monitoring respiratory activities like breathing pattern and it is fastened around the chest and the abdominal area.

  • Two protruding electrodes called galvanometers: They are fastened to the examinee’s fingers and it is used in monitoring sweat gland activity.

The examiner will then have to conduct a functionality test of the lie detector. This is to ensure that the lie detector machine is in perfect shape before the examination commences.

In-test or Chart-collection Phase: This is the stage where the polygraph test takes place. The examiner will put together a minimum of three and maximum of six separate tests with each of them lasting for about 5 minutes.

The examinee’s psychological data will be collected continuously during the test. The collected data will be measured and recorded on the polygraph charts. There will be a two-minute relaxation period between each test.

Once the test has been completed, the examiner will analyze and interpret the collected psychological data. He will also evaluate the collected data and from his professional opinion on the issue. The opinions could be:

  • NDI – No Deception Indicated: The subject is telling the truth

  • DI – Deception Indicated: The subject is not telling the truth.

  • INC – Inconclusive: The evaluation of the physiological data is inconclusive.

  1. Post-test Phase: This is the last phase, the examiner will in this last stage give the result of the test to the examinee. The examinee will be given the chance to explain the various questions he/she reacted to during the test.

The examiner will give the client a verbal report of the lie detector test and the result. This will be followed by a written report that contains the facts and information that were developed during the examination. The examiner’s professional opinion of the result will be based on the analysis, interpretation, and evaluation of the polygraph data.

Systems and Methodology

The polygraph examinations will be administered using top lie detectors instrument companies such as Limestone Technologies Inc. or Lafayette Instrument Company. The lie detector machine to be used should have state-of-the-art systems of computerized polygraph technology. This will ensure that the examination stage will go smoothly and the results will be interpreted and evaluated accurately. Two of the best lie detectors available are Limestone Polygraph Professional Suite and the Lafayette LX4000

The polygraph charts that are collected are evaluated using a numerical evaluation scoring system that has been designed and agreed upon by  the American Polygraph Association.

If the polygraph charts are computerized, they will be further evaluated using a computer software called the PolyScore. This software is a sophisticated and highly reliable scoring system that uses a mathematical algorithm to read the chart.


For most people, the technique behind the use of a lie detector is foreign. This is the reason why most people get scared when they are confronted by the possibility of taking a polygraph examination.

The lie detector machine has 6 different steps or procedures. Of all those, three steps are the most important: Pre-test phase, in-test or Chart-collection Phase and the post-test phase. As an examinee, it is very important for you to be made aware of certain things such as the fact that lie detector test is voluntary. If you don’t feel like doing it, you can simply contact your attorney to cancel the test.

The pre-test stage involves the preparation of the components and the examination questions. The in-test stage is the main questioning and data collection stage. The post-test stage is the final stage where the examiner analyzes, evaluates, interprets the collected polygraph chart and submits the final result.

Knowing this stages will help you overcome any lie detector test that might be required of you later in the future. The process is actually simple and easy.


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