What is a Polygraph Test?

A Polygraph test is often referred to as a “Lie Detector Test”  and is a test used to verify a person’s truthfulness.

lie detector instrumentThe test is performed by a professionally trained polygraph examiner using a computerised instrument.  The polygraph is a scientific instrument designed specifically to record physiological changes such as blood pressure, pulse, respiration and skin conductivity that occur in the human body whilst the subject answers a series of questions. The examiner looks for those changes consistent with deception and forms an opinion about your truthfulness.

The polygraph comprise of:

  • Sensor that records respiratory activity.
  • Measuring device that records sweat and gland activity.
  • Sensor device that records cardiovascular activity.
  • A motion sensor that monitors general movements that might interfere with test data.

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 familiarize 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.

Who would use a Polygraph Test?

Commercial Sector

Since bank employees often are responsible for or have access to large amounts of money and other valuables, banks often use polygraph testing to determine employee honesty and dignity.  Polygraph testing is often used by businesses who have suffered a loss caused by employee theft, sabotage or vandalism.  In these cases the polygraph examinations are set up to gauge employee honesty and loyalty to the company.

Private Sector

Individuals, families and therapists use polygraph examinations to verify statements and to find the truth in a variety of issues, including but not limited to issues involving infidelity, drug use, addictions, sex offenses, physical abuse and other criminal activities.

Legal Community

The polygraph is used extensively by attorneys who wish to provide the best possible defence for their clients.  Many attorneys will submit their own clients to a polygraph examination, while others will use the polygraph to verify statements made by witnesses and other parties to the litigation.

Cases in which to use a Polygraph Test

Criminal and civil caseslie detector test

In some cases related to civil lawsuits or criminal trials, hard evidence is not always available or not always enough.  Polygraph testing is used to bolster evidence or to determine the trustworthiness of a witness.  Polygraph examiners are allowed to testify in criminal and civil cases.  Police often use the polygraph in investigations across the country.

Government: Pre-employment screening

Government agencies hiring employees for sensitive jobs will often use polygraph screening to select candidates.

Issues related to homeland security

The Intelligence Agency of Investigation, National Security Agency and other bodies charged with the nation’s security routinely use polygraphs to uncover crimes and threats against the nation.

lie detector employmentSelecting, employing and retaining loyal employees

Companies can save money and relieve stress by using polygraph testing to expose:

  • Fabricated Curriculum-Vita and Employment History [ CV fact background check ]
  • Drugs and alcohol abuse
  • Fraudulent submission of Overtime /Petty Cash /Petrol Account and other work expenses
  • Theft and work-related misconduct
  • Sexual harassment in the work place
  • Hidden motives for seeking employment
  • Affiliation with gang /criminal elements
  • Gambling Abuse
  • Past & present crimes or misconducts
  • Fraud in the workplace

To this end, PSA provides the following polygraph testing

  • Pre-employment screening
  • Periodic employee testing
  • Selective/random employee testing
  • Employee testing during specific case investigations

Contact Details

Orna Malamud
Milnerton, Cape Town
Tel. 082 492 8577/ 072 457 5846
E-mail: info@polygraphysa.co.za


  • How accurate is a polygraph?
  • Can someone beat a polygraph test?
  • Who designs the questions?