What is a Polygraph?
The word polygraph literally means “many writings”. The polygraph used today is an instrument that records physiological reactions caused by the autonomic nervous system. The instrument records the physiological changes caused by the body’s “fight or flight” reflex. The polygraph records respiration, cardiovascular activity and electro dermal activity, the instrument itself is a combination of several recording devices routinely used in the medical and scientific community.
The polygraph works by tracing changes, in a person’s physiological conditioning during questioning. These changes are recorded directly on to the polygraph charts in order that they can be reviewed.
A polygraph examination is a combination of both a psychophysiological testing technique and an interview.
How reliable is Polygraph Testing?
There is no doubt that the polygraph is highly reliable, providing the person using it is properly trained and the technique they use is validated. The American Polygraph Association (APA) has gathered over 200 studies on the subject. Based on twelve separate studies involving 2174 actual cases since 1980, evidence suggests that qualified polygraph examiners are 98% accurate in their overall decisions.
What happens during a Polygraph test?
A polygraph test will take a minimum of 1.5hours but may take up to three hours. The test comprises of a number of unbiased and objective phases:
- The first phase is the pre-test interview, which includes; obtaining a statement of consent to conduct the test; the completion of a medical questionnaire; an explanation of the equipment; obtaining background data from the examinee and their version of events. During this period, the examiner will discuss the questions to be asked and familiarize the examinee with the testing procedure All test questions are thoroughly reviewed giving the examinee an opportunity to qualify or explain any of their answers.
- The next phase is the collection of data and initially consists of the attaching of the components which routinely includes breathing tubes which are attached around the examinee upper and lower chest area. These tubes record breathing rate, breathing volume and breathing pattern. A standard blood pressure cuff is attached to the examinees upper arm and is inflated to a light pressure immediately prior to the commencement of the test, to record a constant reading of the examinees heart rate and pulse rate; the pressure is then released at the end of the test. Electrodermal activity finger cuffs are attached to two fingers to measure skin conductance (sweat gland activity) and a photo-plethysmograph is attached to another finger to measure blood rate volume. The examinee will be seated on a sensor movement mat. Following this, 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 one or more questions asked during the test. It is important to note that a polygraph does not include the analysis of physiology associated with the voice. Instruments that claim to record voice stress are not polygraphs and have not been shown to have scientific support.
- Chart analysis and post-test interview.
Can you fail the Polygraph test if you are nervous?
Being nervous before a polygraph exam is common and not unusual. Being nervous doesn’t cause a person to fail a polygraph test….lying does.
Is it possible to beat the test?
Provided that examiner conducting the test is trained and qualified it is highly improbable. The polygraph is a medical instrument that records changes in a person’s autonomic reactivity whilst they answer questions, and If a person engages in behaviours in order to distort the polygraph tracings, it becomes evident to a trained examiner when he sees the tracings.
In most cases it is easy for a qualified examiner to determine if an examinee is attempting to alter the outcome of a test. When such behaviour is identified, a result of “purposeful non cooperation” is given.
Are polygraph results admissible in Irish Courts?
Polygraph tests are not intended to be a means for delivering a legal verdict, this is the role of the courts and juries. However there is no reason why the results of a polygraph test cannot be submitted as evidence, the judge will decide in each case whether to allow this evidence to be admitted. The polygraph is no different in many ways to other machines such as x-rays, electrocardiographs etc. whose results are admitted in evidence but interpretation is required by the expert.
Whether the results are used in court or not, polygraph testing has saved investigators and companies huge amounts in investigative costs and resources by narrowing the focus of enquiry and providing further investigative leads.
What should I look for in a Polygraph Examiner?
Ensure the examiner was professionally trained at a polygraph school accredited by the American Polygraph Association and has since undertaken regular ongoing training. They should use the latest computerised equipment and the latest validated techniques. Ensure that your examiner fulfils each of these requirements.
Additionally it is beneficial to look for a polygraph examiner who has professional affiliations and memberships with recognised associations that set professional standards for its members, such as the American Polygraph Association or the British Polygraph Association. Currently there is no Irish Polygraph Association.
Can someone under age 18 take a Polygraph?
Yes, but the examiner must first have written consent of a parent or guardian. However, most examiners will not test anyone less than 14 years old barring extraordinary circumstances.
What Questions Can be Asked?
The examiner will work with you to construct questions that cover the test issue as well as meeting the strict rules for the latest polygraph techniques.
