About the Polygraph

Introduction:

Detection of deception involves results that effect people for the rest of their lives. It is therefore vitally important that you weigh all the facts and verify all the claims before you choose which would produce the best results for you and the community you serve. You will discover what many already know - the only validated, reliable tool for detecting deception is the polygraph instrument!

The polygraph is the only lie detection technique that has proven, independent, scientific, reliability and validity studies and peer acceptance; it is the only lie detection technique directly used by government agencies and private institutions worldwide for investigatory purposes; and, it is used by more state and local law enforcement agencies than any other truth verification technique available.

The Computer Voice Stress Analyser (CVSA), on the other hand, has been proven as invalid and inappropriate for lie detection.

In studies conducted by the US. Department of Defence, based on extensive research done by the Department of Defence Polygraph Institute (DoDPI), clearly demonstrates that "… very few studies have found that voice stress analysis worked better than chance at detecting deception" and "the preponderance of evidence indicates the polygraph is far more accurate at detecting deception than is voice stress analysis."

THE POLYGRAPH

Short history:

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 a polygraph?

The term polygraph literally means "many writings." The name refers to the manner selected physiological activities are simultaneously recorded. Conventional analog instruments could be used but more recently computerised instruments are widely used.

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 mean 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 better. 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 more 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 physiologic 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.

THE COMPUTER VOICE STRESS ANALYSER (CVSA)

Short history:

The Computer Voice Stress Analyser (CVSA) was first used during the Vietnam War by U.S. soldiers in an attempt to determine if Vietnamese prisoners were Viet Cong guerrillas or civilians. During that time it was known as the PSE, or Psychological Stress Evaluator. After the war, private developers took over the technology, but it was not until the late 1980's that the CVSA became more widely used.

How does the CVSA work?

Use of the CVSA revolves around two basic components of speech: Amplitude Modulation (AM), and Frequency Modulation (FM). AM sounds is audible, FM is not.

Under relaxed conditions, the human voice box is under control of the central nervous system. With the onset of stress, as when people lie, changes occur in the voice that causes the inaudible FM component to diminish or disappear. Although inaudible, the change can be detected by the CVSA. Increased stress ultimately results in the loss of the inaudible FM signal. Since this loss can be measured, the CVSA indicates the presence of stress and thus, depending on its application, deception.

The CVSA measures changes in a person's voice caused by stress. Under stress, the nervous system kicks into high gear, sending the voice response into an abnormal range. A normal-range response, the truth, appears as peaks on the CVSA print out. Lies, or stress, look like squared-off blocks.

TRAINING: POLYGRAPH VERSUS VOICE STRESS

POLYGRAPH

Extensive training is necessary to produce a competent examiner. There are no short cuts to polygraph training – it must be all-inclusive. Not only does the training help produce court defensible techniques, it leads to better results and more confessions.

BASIC POLYGRAPH TRAINING INCLUDES:

VOICE STRESS

BASIC VOICE STRESS TRAINING INCLUDES

ACCURACY OF POLYGRAPH RESULTS

During the past 75 years, over 250 different studies have been conducted in this regard. The preponderance of available information indicates the polygraph technique to be reliable in as much as 85% to 98% of specific issue investigations. This proves the polygraph to be more reliable than most, if not all other conventional methods of investigation.

PASA

The Polygraph Association of South Africa (PASA) is an umbrella organisation representing the polygraph examiners in South Africa. Membership to PASA is subject to certain minimum qualifications with regard to training and ethical behaviour.

SELECTING A POLYGRAPH EXAMINER

When a client chooses an examiner, it is very important to ensure that the individual is fully qualified from an accredited polygraph school and is a member of the Polygraph Association of South Africa (PASA)

Source: [ Polygraph Association of South Africa ]