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Polygraph Examinations

A polygraph records the respiration, cardiovascular and electro-dermal activity of a person while they are being questioned. An examiner will then analyze the recorded data and render an opinion as to the truthfulness of the person taking the test. We are able to arrange for polygraph testing to be carried out on-site or off-site by expertly trained and internationally accredited examiners.

What can a polygraph be used for?

Pretty much anything that involves innocence or guilt or the denial of knowledge (or involvement), for example, matters related to:

  • Fidelity/Pre-marital/Marital/Domestic Disputes
  • Validating Innocence
  • Family Law Matters
  • Loss Prevention/Theft/Property Crimes
  • Fraud/Identity Theft
  • White Collar Crimes/Embezzlement
  • Insurance Fraud
  • Hidden Assets
  • Sport Testing/Performance Enhancement Drugs
  • Suspicious Fires/Arson/ Malicious Destruction
  • Missing Persons
  • Work Place Disputes
  • Threat Letters/Emails
  • Sex Offender Testing
  • Allegations of Child Abuse
  • Sexual Crimes and Misconduct
  • Criminal Investigations
  • Allegations of Corruption
  • Alcohol and Gambling Issues
  • Pre Employment Screening
  • Security Vetting Screening
  • Sexual Harassment

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What does a polygraph examination entail?

A Polygraph Examination consists of three separate and distinct phases:

Pre-test Phase
During the pre-test phase, the Polygraphist (Polygraph Examiner) will explain the subject’s legal rights to him or her as well as pointing out the voluntary nature of the examination. Also discussed is the subject’s medical, physical, and psychological background, their knowledge of the investigation, an overview of the questions to be asked and an explanation on how the polygraph apparatus works. In some instances a mock or simulated test will be conducted to familiarize the subject with the procedure.
Testing Phase
The polygraph examination takes place during this phase. Once the examination is underway, the examiner will administer a minimum number of three separate tests each lasting approximately 5 minutes. The subject will have a two-minute relaxation period between each test. Upon completion of this phase, the examiner will analyze, interpret and evaluate the data collected during the polygraph examination, after which the examiner will form one of the following professional opinions:

NDI – No Deception Indicated
DI – Deception Indicated
INC – Inconclusive
Post-test Phase
During this last phase, the examiner provide the subject with the result of the polygraph examination. If the physiological data recorded on the charts shows reactions on the part of the subject to the relevant questions that were asked, he or she will be given the opportunity to explain these reactions. Once the post-test phase is complete, the examiner will provide the client with a verbal report of the polygraph examination and its result. This will be followed, in a timely manner, by a written report containing a factual account of all the information developed during the polygraph examination, as well as the examiner’s professional opinion of the examination results based on the analysis, interpretation and evaluation of the polygraph data.

How does a polygraph work?

There are two parts to a polygraph examination: one are the questions being asked of the subject and the other is the polygraph instrument itself.


The polygraph will collect a range of physiological data from at least three systems in the human body. Commonly these would be respiration, cardiovascular and electro-dermal activity. Convoluted rubber tubes that are placed over the subject’s chest and abdominal area will record respiratory activity. Two small metal plates, attached to the fingers, will record sweat gland activity / skin conductivity, and a blood pressure cuff, or similar device will record cardiovascular activity. In addition, activity sensors in the examination chair can be used to detect and measure subtle and gross movements.


Several questioning techniques can be used in polygraph examinations. The most commonly used test is the Control Question Test (CQT). The CQT compares responses to “relevant” questions (e.g., “Did you steal the money?”), with those of “control” questions. Control questions usually concern acts that are similar to those being investigated, but are related to the subject’s past and are usually broad in scope; for example, “Have you ever stolen anything before?”

A person who is telling the truth is assumed to fear control questions more than relevant questions. This is because control questions are designed to arouse a subject’s concern about their past truthfulness, while relevant questions ask about a act they know they did not commit. A pattern of greater physiological response to relevant questions than to control questions leads to a diagnosis of “deception indicated”. Greater response to control questions leads to a diagnosis of “no deception indicated”. If no difference is found between relevant and control questions, the test result is considered “inconclusive.”

An alternative questioning technique is known as the Guilty Knowledge Test (GKT). A GKT involves developing a multiple-choice test with items concerning knowledge that only a guilty subject could have. A test of a theft suspect might, for example, involve questions such as “Was R500, R1,000, or R5,000 stolen?” If only a guilty suspect knows the correct answer, a larger physiological reaction to a correct choice would indicate deception. With a sufficient number of items, a psychometrically sound evaluation could be developed.

Must polygraph examiners be accredited?

polygraph-associationsAbsolutely. Accreditation not only ensures that the polygraph examiner is qualified to administer and interpret the results of a polygraph examination, but also that he or she adheres to strict codes of conduct and professional duty that are periodically evaluated.

The polygraph examiners that will administer your polygraph examination are members in good standing and/or are accredited by the following associations.

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