What is a polygraph?

The term “polygraph” literally means “many writings.” The name refers to the manner in which selected physiological activities are simultaneously recorded. Polygraph examiners may use conventional instruments, sometimes referred to as analogue instruments, or computerized instruments. It is important to understand what a polygraph examination entails. A polygraph will collect physiological data from at least three systems in the body.

Corrugated rubber tubes (or electronic sensors) placed over the examinee’s chest and abdominal area will record upper body activity. Two small metal plates or disposable adhesive sensors, attached to the fingers, will record NACVSA_Exposes_Inaccuracies_Polygraph_Testssweat gland activity, and a blood pressure cuff or similar device will record cardiovascular activity. Some instruments also monitor other activity. For example, a finger plethysmograph, which monitors blood volume in a fingertip, or motion sensors, which monitor general movements that might interfere with test data, are often used. It is important to note that a polygraph does not include the analysis of physiology associated with the voice. Instruments that claim to record voice stress are not polygraphs and have not been shown to work any better than chance (i.e. accuracy is similar to making a decision based on a coin toss).

A typical polygraph examination will include a period referred to as a pre-test interview, a chart collection phase and a test data analysis phase. During the pre-test, the polygraph examiner will complete required paperwork and talk with the examinee about the test, answering any questions the examinee might have. It is during this phase that the examiner will discuss the test questions and familiarise the examinee with the testing procedure. During the chart collection phase the examiner will administer and collect a number of polygraph charts. The number of questions and the number of charts will vary, depending on the number of issues and technique employed. Following this, the examiner will analyse the charts and render an opinion as to the truthfulness of the examinee. The examiner, when appropriate, will offer the examinee an opportunity to explain physiological responses in relation to one or more questions presented during the test.

Types of Polygraph Examinations

Specific Examinations

Tests that are case specific, the topics include theft, arson, crimes against persons, crimes against property, crimes against children, white collar crimes and fraud of any kind.

Specialised Testing

These tests are focused on sex offenses, testing of both suspects and the more sensitive confirmatory tests of victims.

Evidentiary Examinations

Tests aiding in locating of evidence, or possible property recovery. Also used in searching of guilty knowledge of evidence.

Pre-Employment Screening

Tests involving the background screening of an individual before they are considered for employment. Screens for history of workplace theft, fraud and other behaviours. Determines potential employee’s personal honesty and integrity.

Periodic / Routine Testing

Persons needing to be tested on a regular basis, may include security personnel, armed response personnel and personnel handling money or any other valuable merchandise.

What to look for in an Examiner

  1. Ask to see accreditation from a recognised governing body such as S.A.P.P.A (South African Professional Polygraph Association) or the A.P.A (American Polygraph Association). Accreditation from either of these organisations will suffice.
  2. Ask if they are using the latest technology, for example the Lafayette LX-4000, or even better, the LX-5000.
  3. Ask if the examiners equipment is calibrated and to see their calibration certificate. Equipment needs to be calibrated every six months.
  4. Ask if the examiner is taking the appropriate steps to conduct a thorough examination. Does your examiner do a Pre-Test Interview?
  5. Ask if your examiner video records all examinations for possible later quality review.
  6. Does the examiner make use of a quality control process?
  7. Are you being charged a market related price (between R750 and R950 for standard tests and R 1250 for specialised tests)
  8. Is your examiner gathering enough relevant information from you to thoroughly understand and investigate the issue which is being tested?
  9. Is your examiner able to professionally answer any questions relevant to the polygraph process that you may have?

Go with your first instinct. Does your examiner make you feel at ease and conduct themselves in a professional manner?


Exactus charges between R750 and R950 per test, for standard tests and R1250 per test, for specialised testing. A market related price is charged for travelling when testing is outside of a 50 km radius of Emalahleni (Witbank). Rates are negotiable when there is a large number of persons that need testing (10 or more).