A polygraph test, popularly known as a “lie detector test”, is a device that captures basic types of psychological data – usually differential blood pressure, heart rate, respiration rate and skin conductance. A person being examined by the use of this device will typically fear being ‘caught’ lying and his body will react reflecting that fear, which reactions are then captured by the polygraph test. But can ‘failing’ a polygraph test constitute grounds for dismissal of an employee?

The use of polygraph testing has been in existence for decades and has over the past few years also gained popularity amongst employers in South Africa in respect of internal investigations and screening of job applicants for placement in senior positions. The controversy linked to polygraph testing in the context of employment law however, remains an issue that has had the CCMA and Labour Courts grappling with when to accept the usage of this test in the workplace without having to conclusively rely on its results to justify an employee’s dismissal.

The right to fair labour practices which includes the right not to be unfairly dismissed is one of the cornerstones on which our employment law is founded. Requirements for a fair dismissal are firstly that there must always be a fair reason for the dismissal. In other words the gravity of the misconduct committed by the employee must be so serious as to warrant dismissal. Secondly, the dismissal must have been effected in accordance with a fair procedure which in its most elementary form requires that there must be a dialogue (commonly referred to as a disciplinary hearing) between the employer and employee before a decision is taken to dismiss the employee.

The use of a polygraph test comes in handy for employers in cases where employees are accused of misconduct (e.g. cases of fraud, wilful damage to property, dishonesty and theft) and internal investigations are underway. The risk however becomes high when an employer’s case for disciplinary action stands or falls on the results of the polygraph test.

Generally, employers are permitted to use polygraph tests to investigate specific incidents such as where employee(s) had access to the property which is the subject of the investigation; there is a reasonable suspicion that the employee was/could have been involved in the incident; there has been economic loss or injury to the employer’s business like theft of company property; the employer is combating dishonesty in positions of trust; the employer is combating serious alcohol, illegal drugs or narcotics abuse; fraudulent behaviour within the company; deliberate falsification of documents and lies regarding the true identity of persons involved.

Currently there is no specific legislation controlling the use of the polygraph test or regulating the protection of the rights of employees against abuse of this test. In general however, it remains unlawful to force an employee to undergo a polygraph test unless he or she consents to it, with such consent to preferably be in writing. Such consent can also be included in a contract of employment concluded with an employee.

In practice, a polygraph test cannot serve to prove that someone is lying as the questions are often too broad to exclude that which is neither intended nor sought. It most definitely does not prove that someone is guilty. It is merely an indicator of deception. Our courts have accepted that polygraph tests can do no more than prove the existence or absence of deception and cannot prove that a person is guilty of a crime. A failure by an employer to adhere to the rules relating to the use of polygraph tests will prejudice the case of an employer and cause the case to be seen as unreliable if the polygraph test forms the basis of the case against an employee. Where polygraph evidence is to be accepted as relevant in any hearing, such tests may be taken into account but must at the very least be supported by other evidence and will not be accepted purely on its own.

It is clear that the results of a polygraph test on its own without any supporting evidence cannot constitute a ground for dismissal. At best only an inference can be drawn from the failure of the test. In the absence of expert evidence by a polygraphist to explain what the inference is, the use of the test is also limited. This should not be construed to mean that polygraph tests may not be taken into account – its relevance may however be limited depending on the availability of expert evidence by a polygraphist to support the findings and the availability of further supporting evidence.

The value of polygraph evidence remains an open question to be determined on the merits of each case. Where it is to be used as evidence, expert evidence of its clarity and accuracy will be important for reliance thereon and employers should tread carefully when using a polygraph test as the sole grounds for pursuing a dismissal.