Frequently Asked Questions about the Polygraph Examination

What is a Polygraph?

The term "lie detector" is a very popular, but misleading, name for the polygraph examination. In Greek, the word polygraph means "many writings." The polygraph instrument was so named because it makes various simultaneous recordings of physiological changes that occur in a person's body. In actuality, the polygraph instrument should be called a "truth verifier." Statistics show that in the vast majority of instances, the polygraph instrument verifies the truthfulness of your statements.

There are many misconceptions about a polygraph examination. For example, it is widely assumed that the polygraph examination is wrapped in secrecy and that its success depends on keeping it secret. Nothing could be further from the truth! Remember, questions are encouraged. The examination you are about to take will be explained in detail by a trained professional polygraph examiner.

The examiner will explain how the polygraph instrument operates, how it records your body's physiological responses when you lie and tell the truth, and every question to be asked of you in the polygraph examination will be discussed with you "word for word."

How does the Polygraph Work?

The computerized polygraph instrument is sometimes called a truth verifier or lie detector because it is used to verify the truthfulness of your statements. The computerized polygraph instrument is an extremely sensitive recording device which is used to measure physiological changes in your body such as blood pressure/volume, heart rate, and certain resistance changes. The insturment does this through a series of devices which are attached to your body. The attachments are painless and do not require disrobing.

The computerized polygraph instrument does not interpret, it only records. In other words, if your heart is beating 72 beats per minute at the time a question is asked of you, it will record that fact of 72 bpm on the computer screen. The instrument does not measure something that is not there, nor does it pre-judge. It records functions which are controlled by the autonomic, or involuntary, nervous system.

What does this have to do with Verifying the Truth?

When a person tells a lie, a number of physiological changes take place in the body over which an individual has no control. For example, the heart begins to beat faster, pupils dilate, sweat flows in the skin, blood flow to the brain increases, salivary glands in the mouth dry up, adrenaline is produced causing additional physiological changes and muscle tenstion. These changes are simultaneously recorded by the polygraph instrument and transferred onto the computer. The highly trained professional polygraph examiner can evaluate the charts with extreme accuracy and determine whether the person is being completely truthful.

What does the Polygraph Examination Consist of?

The polygraph examination consists of 3 phases: the pre-test, in-test (examination), and the post-test.

The pre-test phase consists of a review of the information provided by the examinee, an explanation of how the polygraph works, and a "word for word" review of all questions to be asked during the examination.

The in-test (examination) phase consists of the polygraph components being placed on, or attached to, the examinee, and a series of polygrams or charts being completed. Again, you will only be asked those questions that have already been reviewed. The post-test phase consists of an evaluation of the examination charts produced by the examinee and a review of the examination results with the examinee.


1. All you have to do is relax, follow directions, and tell the truth.

2. If there is something you do not understand, ask your examiner to explain it.

3. All questions will be discussed with you prior to the examination.

4. The examination is voluntary.