Polygraph Examinations

illumico was founded initially as a polygraph testing agency; its examiners are well qualified, affiliated to all the national agencies and have a wealth of experience which has brought successful results to their clients.

History of the Polygraph
The first person to utilise an instrument for the purpose of detecting lies was C Lombroso in 1895. He measured changes in blood pressure and pulse rate with a hydrosphygmograph. J Larson (1921) was the first person to use a continuous method of recording changes in blood pressure and pulse rate in more than one recording to detect deception. In 1926, Keeler developed a more complex recording instrument, utilising blood pressure changes, pulse rate and respiration. He added the galvanograph in 1936. The first electronic polygraph was introduced in 1974 by Stoelting Co.


In 1952, Reid developed an improved questioning technique by adding control questions. The first polygraph school was opened by L Keeler in 1948. In 1961, Backster developed the Zone Comparison question technique. Several studies on the polygraph have been conducted in the USA in recent years and continuous research and development is taking place in the field.

What is the Polygraph?
The term polygraph literally means "many writings." The name refers to the manner selected physiological activities are simultaneously recorded.
How does the Polygraph work?
Deception is an integral part of human nature. Although deception is usually seen as morally wrong, it is part of everyone's existence. Deception is usually linked to gaining some unjust advantage or avoiding negative consequences. This means that deception is usually deliberate.

The working of the polygraph is based on the recording and interpretation of psycho physiological changes in the body when someone is answering particular questions. These changes are the result of messages received through the autonomic nervous system. "Autonomic" means automatic or involuntary, so it deals with those aspects of the body that cannot be controlled voluntarily. It is helpful in the detection of deception because the individual being examined is unable to control these reactions in the body.

There are two branches to the autonomic nervous system. The first one has to do with growth and development, and the second one is an emergency system. These two parts operate in opposition to one another, which means that only one (usually the part that has to do with growth) is in control at any time. The emergency system becomes dominant only when there is some threat to an individual and he or she becomes fearful. For example, if you are walking down the street and a man suddenly approaches you and pulls out a knife, you will be alarmed. That message will register in the brain, and the brain in turn will send a message back to the autonomic nervous system to put the emergency system in control. When that happens, a series of physiological changes takes place that helps you cope with that situation. Your heart, for instance, contracts more quickly and strongly, which sends more blood throughout the body and provides it with nourishment in order to function more effectively. Your liver secretes sugar, giving you more energy, and the pupils of your eyes dilate so you can see well. The palms of your hands perspire so that you can grasp things more effectively, just as a baseball player spits on his hands to get a better grip on a baseball bat. These and other changes occur, allowing you to run faster, hit harder, or elevate so that you can get out of that dangerous situation.

The Polygraph instrument records these physiological responses through four sensors. If you tell the truth, you will function at your normal physiological level. If you are asked a question to which you are going to lie, your brain will register a threat because you do not want to be caught in a lie. As soon as your brain registers the threat, your body automatically shifts into the emergency system. There is no way in which you can stop or control the physiological changes that will take place. It is this involuntary response, as opposed to spoken words.

The Polygraph records physiological responses and the polygraphist interprets the changes that occur in response to various questions. During a polygraph examination the threat is associated with being caught in a lie because of the possible consequences. Therefore the examinee's deceptive responses cause sympathetic arousal and some of the physiological changes that occur are then recorded. Once the subject responds and the deception is over and with it the threat, the Parasympathetic Nervous System being the strong dominant system fights to regain control and there is a sudden return back to the normal state. Because the individual does not have control over physiological responses, the recording of these changes in the body, by the polygraph, remains one of the most effective methods of establishing truthfulness.

Procedures followed during an examination
A typical Polygraph examination will include periods referred to as a pre-test phase, a chart collection phase, post-test phase and a test analysis phase. This procedure usually takes one to one and a half hours.

  • In the pre-test phase, the polygraph examiner will complete required paperwork and explain the theory of the polygraph in an understandable way to the examinee. The examinee will be given the opportunity to discuss their roles or perceptions regarding the case under investigation and provide relevant information. During this period, the examiner will discuss the questions to be asked and familiarise the examinee with the testing procedure.
  • During the chart collection phase, the examiner will administer the examination and collect a number of polygraph charts. No questions will be asked during the examination that have not been discussed and reviewed with the examinee.
  • In the post-test phase, the examiner will analyse the charts and render an opinion as to the truthfulness of the person taking the test. The examiner, when appropriate, will offer the examinee an opportunity to explain physiological responses in relation to any questions asked during the examination.

For more information regarding our Polygraph Services please contact us

About Us

Through integration and convergence, illumico has the advantage to provide a full system design, installation and backup service to effectively achieve this. With the growing need for specialised services within the security industry, illumico provides a range of products and services to take proactive steps in combating crime and effectively reduce risk.

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For general information about the services/products/off site monitoring please contact us at:
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