1. What is a polygraph?
Derived from the Greek language, the word "polygraph" means "many writings". It refers to the manner in which selected physiological activities are continuously and simultaneously recorded.
A polygraph is a diagnostic instrument used by a formally trained polygraph examiner for the purpose of collecting, measuring, and recording selected physiological data obtained from an examinee as he or she answers a series of questions relating to a specific issue — whether criminal, civil, or private — during a polygraph examination. This data will then be analyzed and evaluated for psychophysiological credibility assessment.
Polygraph examiners may use conventional instruments, sometimes referred to as analog instruments. Since the early 1990s, however, most polygraph examinations are administered using computerized polygraph instruments.
With conventional polygraphs, physiological responses are continuously and simultaneously recorded in graphical form using inked pens on a moving roll of chart paper.
The development of medical-grade instrumentation and software has allowed for computerized polygraphs to record physiological responses directly to a software program and display this data on a computer monitor. Chart analysis is done on a screen, rather than on a roll of chart paper, and can also be printed out.
During a polygraph examination, the polygraph instrument detects, measures, and records physiological data obtained from three major systems in the human body, all of which are controlled by the Autonomic Nervous System:
1) Cardiovascular System: Heart rate, relative blood pressure, blood volume;
2) Respiratory System: Respiratory activity patterns and changes;
3) Electrodermal System: Galvanic skin response, i.e. sweat gland activity.
The polygraph is an instrument that is used to detect and record human physiology. It is the job of the examiner to analyze, interpret, and evaluate the physiological data collected during the polygraph examination and then form a professional opinion as to the truthfulness of the examinee based on the evaluation of this data.
The polygraph instrument is often referred to as a "lie detector".
2. How accurate is a polygraph examination?
Polygraph examinations have gained general acceptance in the scientific fields of psychology and psychophysiology in those areas devoted to credibility assessment. Research conducted by the relevant scientific community, government organizations, and independent universities clearly indicates that a polygraph examination — when properly administered by a formally trained and competent polygraph examiner, adhering to federal standards of procedure and instrumentation — has a high level of accuracy in verifying the truth and detecting deception.
According to Dr David C. Raskin, the world-renowned expert and leading scientist in the field of polygraphy, the scientific data concerning the validity of the polygraph can be summarized as follows:
"High quality scientific research from the laboratory and the field converge on the conclusion that a properly conducted CQT (Comparison Question Test) is a highly accurate discriminator of truth tellers and deceivers. The research results converge on an accuracy estimate that exceeds 90 percent."
According to the American Polygraph Association, 80 research projects, which included both laboratory and field studies, have been conducted and published since 1980 on the validity and reliability of polygraph testing. These projects involved approximately 6,300 polygraph examinations. Of the 23 field studies conducted, the accuracy of polygraph testing was estimated to be 95 percent. Of the 57 laboratory simulation studies conducted, the accuracy of polygraph testing was estimated to be 81 percent.
Like any other diagnostic instrument that is used to measure human physiology for the purpose of evaluation and forming professional opinions thereupon, the polygraph instrument is not infallible. The relevant scientific community agrees, however, that polygraph examinations have a very high probative value in distinguishing truthful individuals from deceptive ones, and that no other alternative testing technique for truth verification and lie detection performs better.
3. Will I feel pain during the polygraph examination?
No. Some people are concerned that they might get an electrical shock as a result of being connected to the polygraph instrument. Be assured there is no possibility of this. The only sensation that people will feel is a slight pressure on the upper left arm where the standard blood pressure cuff is applied and inflated for about 3 to 5 minutes during which time the test questions are asked. The blood pressure cuff is the same as that used by doctors and nurses to measure your blood pressure.
4. Can I be forced to take a polygraph examination?
No. To properly administer a polygraph examination, the examiner will ask you to sit still and not to move needlessly while the examination is in progress. The examiner will also ask you to breathe normally, not to take deep or short breaths, not to hold your breath or to modify it, as all such manoeuvres could cause problems for the analysis of the physiological data recorded by the polygraph instrument. Since the examiner requires your full cooperation in this regard, you must voluntarily accept to undergo a polygraph examination.
If you do not want to submit to a polygraph examination, you can exercise your right of refusal.
5. I am telling the truth, but I am nervous about taking a polygraph examination. How does the examiner distinguish between the state of nervousness in a person and the reactions that are manifested following a lie?
It is normal for an innocent person to be nervous about taking a polygraph examination and the competent examiner is aware of this fact. Nervous reactions recorded on the polygraph charts are not interpreted by the examiner as a manifestation of deception because the tracings of these reactions are very different from those recorded when a person is deliberately lying.
Once the examination is in progress, the examiner wants you to be as comfortable as possible. To this end, he or she will do their best to reduce your degree of nervousness before the examination gets underway.
6. I suffer from hypertension. Can this condition affect the result of the polygraph examination?
While the polygraph does measure and record blood pressure, hypertension does not cause physiological reactions that are characteristic of those obtained when a person is lying. More precisely, a lie represents a different curve on the polygraph charts than one produced as a result of hypertension. A truthful answer is evident to the examiner even if the examinee suffers from high blood pressure.
Be sure to inform the examiner if you are being treated by a medical professional for hypertension or any other medical condition.
7. Can drugs or medications affect the result of a polygraph examination?
Antidepressants, such as Lithium, Prozac, Valium, Xanax, and Betablockers, can affect the result of a polygraph examination in that they can bring about an inconclusive result. For some people, however, these drugs will have no effect on the result. Contrary to some claims, drugs and prescription medications do not allow a person to "beat" a polygraph examination.
During the pre-test interview, the examiner will establish the examinee’s physical, psychological, and physiological history to determine whether he or she is fit to undergo a polygraph examination. Here, the examiner will ask the examinee specific questions about any prescribed medications or drugs he or she may be taking that could affect the result of the examination.
8. Will I know beforehand what questions I will be asked during the polygraph examination?
Yes. During the pre-test interview, the examiner will formulate and review with you all the questions that will be asked during the polygraph examination. There will be no surprise or trick questions.
9. How long does a polygraph examination last?
A polygraph examination lasts about 2 hours. Some can last more or less time depending on the complexity of the issue under investigation. All polygraph examinations are audio and video recorded.
10. Will I be given the result of my polygraph examination?
Yes. You will be given the result of your polygraph examination immediately after the charts have been analyzed and evaluated. The examiner will then take the time to discuss the result with you. If the physiological data recorded on the polygraph charts show reactions on your part to one or more of the questions asked during the polygraph examination, you will be given the opportunity to explain these reactions.
11. How does the polygraph instrument work?
Since the early 1990’s, most polygraph examinations are administered with the use of computers. The computerized polygraph instrument and its components continuously and simultaneously collect, measure, and record physiological data obtained from at least three major systems in the human body (i.e., cardiovascular, respiratory, and electrodermal), all of which are controlled by the Autonomic Nervous System. This data will be analyzed and evaluated, and a professional opinion will be rendered by the examiner as to the truthfulness of the examinee when answering the relevant questions asked during the polygraph examination.
12. What is the procedure during a polygraph examination?
A polygraph examination comprises three phases.
1) Pre-test Phase (Information collection);
2) In-test Phase (Chart collection);
3) Post-test Phase (Data analysis).
For more information on this question, please refer to the section entitled "POLYGRAPH PROCEDURE" .
13. Who uses polygraph examinations today?
Polygraph examinations are used in more than 50 countries by government organizations, law enforcement agencies, private security firms, the legal community, the corporate sector, and private citizens.
14. Has this information provided you with an answer to your question?
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