A polygraph is a diagnostic instrument used by a formally trained polygraph examiner for the purpose of collecting, measuring and recording physiological data from three major systems in the body. The Cardiovascular system (heart rate, blood pressure, blood volume), the Respiratory System (respiratory activity patterns and changes) and the Electrodermal System (galvanic skin response)

The most important considerations are training and experience. Some of the things to consider are:

Is this business engaged solely in providing a polygraph service?

Where did the examiner receive their training? Is this school accredited by the American Polygraph Association? Are they certified? What advanced training do they have?

Do they use state of the art computerized equipment?

What education degrees do they have?

It is important to add that the examiner must be properly trained, use an approved technique and accurately interpret the charts produced.

The polygraph examination consists of three components. The pre-test, the test and the post test.

During the pre-test the examiner will gather all relevant information available regarding the issue(s) to be tested. He will explain your rights and ask you to sign a consent form. He will determine your ability to be polygraphed by completing a questionnaire. This will also make the examiner aware of any health or other issues that might affect the conduct of the examination. He will talk about the reason for the examination and ask about your side of the story. This will be followed by an explanation of how the polygraph works. At this point all of the questions that will be asked are reviewed with you and may be modified if you do not understand them. Once you indicate that you are satisfied with the questions we move to the test portion of the examination.

A practice exam will be conducted to determine that you are capable of responding physiologically when you tell a lie. It will ensure the examiner that the instrument is adjusted properly. It will let you see what it feels like to have the sensors connected.

Once this is completed the actual polygraph will be conducted. The test questions will be formulated and reviewed with you word for word. All questions will be answered with a yes or a no. No questions will be asked without being reviewed with you, there will be no surprise or trick questions asked. Only when both you and the examiner are satisfied with the questions will the examination proceed. The examination is conducted by asking the questions while you are attached to the polygraph. The questions will be asked a number of times and the data will be collected and recorded. When he has collected sufficient data he will remove the components from your body

During the post test phase the examiner will carefully analyse the charts produced and render an opinion based solely on the polygraph. He will discuss the results with you.