Credibility Assessment of Maryland Polygraph Services

A polygraph test consists of several different phases: a pretest interview, the collection of charts, and an analysis of the polygraph charts. The average polygraph test will usually last two to four hours from beginning to end. The longest part of the polygraph test will be the pretest interview, which normally lasts anywhere between 45-90 minutes.

During the pretest interview, the polygraph examiner will explain your legal rights, explain the polygraph instrument and how it works, discuss the issue, develop and review all questions asked on the polygraph test, cover general background information, and will provide instructions for the actual testing phase.

The polygraph consists of three or more components: the pneumograph component that records respiration and movement, the galvanograph or GSR component records your galvanic skin response and changes in skin resistance, and the cardiosphygmograph component records your relative blood pressure and pulse rate. Once the pretest interview has been completed, the polygraph examiner will place four attachments on the subject's person: two rubber pneumograph tubes across the upper chest and abdomen, two metal fingerplates across the ring and index finger, and a blood pressure cuff around the upper arm. During the collection of charts, the examiner will ask the reviewed questions two to three times, and run a minimum of two to three separate charts before rendering an opinion.

It is expected that anyone who takes a polygraph test will be nervous; however nervousness does not normally interfere with the test. Even though a person has high blood pressure, diabetes, etc., their body has a set of normal patterns on a daily basis. When a person decides to lie, however, physiological changes begin to take place in the body. Blood pressure begins to increase or decrease. Heart rate can increase or decrease. A person's heart can skip a beat. Blood volume begins to change. These are just a few of the types of physical changes that can occur. In the case of deception, more than one type of physiological change usually occur. The person taking the test must decide whether or not they are going to tell the truth, or whether or not they are going to lie and withhold information about the relevant issues. Once a person decides to tell the truth, the body goes about its normal patterns with no significant or consistent changes.



According to the National Center for Credibility and Assessment and the American Polygraph Association, over 250 studies have been conducted on the accuracy of polygraph testing during the past 25 years and it is estimated that the accuracy of decisions is generally in the range of 85-95% for specific issue investigations. Some of the most frequent errors may be caused by lack of training,non-functioning equipment, failure to properly prepare the examinee for the examination, poorly worded test questions, failure to assess the examinee's emotional and physical condition, improper use of testing techniques, a lack of quality control review, and misreading of the physiological data on the polygraph charts.


Fees for polygraph services usually depend upon the complexity and type of polygraph test to be conducted and the average polygraph test will take between two to four hours. The examination will include a detailed pretest interview, collection of charts whereby the examiner will administer a number of polygraph charts, and an analysis of the polygraph charts. If you select a polygraph examiner solely on the basis of rates, you should understand that shortcuts in time and service may lead to errors and future legal problems. The cost of a polygraph exam will vary and depend upon the issues involved.

If you are interested in obtaining specific costs, contact CAM Polygraph Services for a free initial consultation to evaluate your polygraph needs.