How accurate is a polygraph examination?

Research conducted by the scientific community, government agencies and independent universities clearly indicates that a polygraph examination — when properly administered by a professionally-trained and competent polygraph examiner, using federal standards of procedure and instrumentation — has a high level of accuracy in detecting truthfulness or deception.

According to the American Polygraph Association, 80 research projects were listed since 1980 involving more then 6000 polygraph examinations. Researchers conducted 23 studies on the validity and reliability of polygraph examinations in field settings which provide an average accuracy of 95%. 57 studies were conducted in laboratory simulation which provided an average accuracy of 81%.

Like any other instrument that is used to measure human physiology for the purpose of forming professional opinions, the polygraph is not infallible. However, the scientific community agrees that polygraph examinations, as they are being used today, have great probative value in detecting truthful persons and deceptive ones.

How does a polygraph instrument work?

Through the use of the polygraph instrument and its various components, the examiner will analyze various timely physiological responses that are not under the examinee's control to determine if a truthful or a deceptive answer was given.

Will I feel pain during the polygraph examination?

No. The only sensation that you may feel is a slight pressure on the arm caused by the blood pressure cuff. This is the same cuff used by medical practitioners to measure your blood pressure.

Can I be forced to take a polygraph examination?

No. Since the examiner requires your full cooperation, you must volunteer to undergo a polygraph examination. If you do not want to take a polygraph examination, you can at any time exercise your right of refusal.

How does the examiner differentiate nervousness from reactions manifested following a lie?

It is quite normal for a person to be nervous when taking a polygraph examination, whether they intend to lie or not, and the experienced examiner is aware of this fact. Nervousness will not interfere with the examiner's ability to distinguish honesty from dishonesty as they are clearly and completely different reactions. Once the examination is in progress, the examiner will want you to be as comfortable as possible. To this end, the examiner will do his best to reduce your degree of nervousness prior to the actual examination.

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 typical of those obtained when a person is lying. More precisely, a lie represents a different curve on the polygraph charts from one that is produced as a result of hypertension. Be sure to inform the examiner if you are currently undergoing treatment for any medical conditions.

Can drugs or medications affect the result of a polygraph examination?

Contrary to some claims, drugs and medications do not allow a person to "beat" a polygraph examination. During the pre-exam interview, the examiner will make sure the examinee will be fit to undergo an examination. Furthermore, the examiner will verify any medication taken by the examinee to ensure that it will not affect the outcome of the examination.

Can I know beforehand what questions I will be asked during the polygraph examination?

Yes. During the pre-test phase, the examiner will formulate and review with you all the questions that you will be asked during the polygraph examination. The polygraph examination will have no surprise or trick questions.

How long does a polygraph examination last?

A polygraph examination lasts about two hours. However, every examination is different; some can last more or less depending on the complexity of the issue.

Will I be informed of the result of my polygraph examination?

Yes. Each person who is submitted to a polygraph examination will be informed of the result immediately after the polygraph charts have been analyzed. The examiner will also take the time to discuss and clarify the results with the examinee.

How are polygraph examinations being used today?

Polygraph examinations are being used around the world by government, law enforcement and security agencies, the legal community and private sector.

Has your question been answered?

If your question has not been answered, please do not hesitate to contact us. We will be happy to answer any questions you may have.

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Polygraph Examination Service - Canada

Polygraphist expert, Sergeant Michel Côté has spent over twenty years in the fields of policing, investigations, intelligence and military operations