The use of a polygraph test, commonly referred to as a lie detector test and is currently unregulated in South Africa. The test is administered by a Polygraphist who measures and records the physiological indices such as blood pressure, pulse, sweat glands and cardiovascular responses of the person being test, while the subject is asked a series of questions with yes or no answers. The test is devised to determine the truthfulness of the questions posed.
When Polygraph evidence is presented to the CCMA, the test may not be interpreted as applying guilt. The evidence may only be used collectively with other evidence in the finding of guilt of an employee. Polygraph evidence is merely supportive and fulfills the purpose of an investigative tool and not stand alone uncorroborated evidence.
Polygraphists have become accepted as expert witnesses in CCMA, thus the admissibility and reliably of the evidence must be tested. The Polygraph evidence will only be admissible if the person who conducted the test is a qualified to testify as an expert.
According to Truworths Ltd v CCMA and Others (2008) JOL 22565 (LC) The Commissioner cannot disregard polygraph evidence but has the discretion to determine the weight of the evidence. When Polygraph evidence is uncorroborated, the evidence shall bear little weight.
In Mustek Ltd vTsabadi NO & Others  8 BLLR 798 (LC), the Court determined that Polygraph evidence by itself, is insufficient evidence to justify the dismissal of an employee. Thus, Polygraph evidence has little value where it is not supported by further evidence linking the employee to the offence.
Employers should take care when making use of Polygraph tests results as the basis for dismissal.