What is a polygraph?
A professional polygraph examination has three phases: a pretest phase, data collection (the test) phase, and a post-test phase, which includes test data analysis. A typical polygraph examination will last at least 90 minutes, and sometimes longer.
In the pretest phase, required paperwork is completed and the polygraph examiner gets to talk with the examinee about polygraph and the issue being tested.
The data collection or "test" phase takes place in a quiet room where distractions are held to an absolute minimum. The examiner will attach the sensor components to the person and then ask the previously reviewed questions that are designed to be answered “yes” or “no”. Data is collected by the sensors and instrument and a computerized recording of physiological responses is obtained.
In the post-test phase, the examiner will analyze and score the chart data and render an opinion as to the truthfulness of the person being examined.
Are polygraphs reliable?
The polygraph has been in use for over 75 years. During that time approximately 250 studies have been conducted on the accuracy of polygraph tests. Since conditions and factors involved in research will vary, and since a polygraph examination is a very complex process, it is difficult to extract a precise accuracy figure from the data. Nevertheless, the preponderance of available information indicates that the accuracy of a properly trained examiner, utilizing established testing procedures, is around 95% for specific-issue investigations.