Many employers labour under the misapprehension that polygraph results are easily admissible as evidence in disciplinary proceedings. Others believe that polygraph results are strictly inadmissible and unusable. In truth, the answer lies somewhere in-between. Employers should be asking what steps should be followed to allow polygraph evidence in disciplinary proceedings.

Such a question recently came before the Labour Appeal Court (LAC) in the case of DHL Supply Chain (Pty) Ltd v De Beer NO and others (DA4/2013). In essence, this case involved an employer who noticed stock had gone missing. The employer's employees were subjected to a polygraph test. The two employees who failed were dismissed as a result. The employer was unsuccessful at the Commission for Conciliation, Mediation and Arbitration (CCMA) and took the case on review. The employer was unsuccessful on review and took the matter on appeal to the LAC, claiming that proper weight was not afforded to the polygraph tests.

In its judgement, the LAC quoted the arbitrator's award: "Polygraph evidence, when coupled with other circumstantial evidence, can be sufficient to discharge the onus in labour disputes" and circumstantial evidence is "indirect evidence which creates an inference from which a main fact can be inferred". The LAC went further to ask "what was polygraph evidence worth in the context of all the facts?" The answer was that, in isolation, it was not worth much.

Clutching at straws, the employer then claimed that even if the claim of theft was unproven, "the taint of suspicion has undermined the requisite degree of confidence which is an operational necessity". While trust is a vital factor in the employment relationship, the LAC found that suspicion alone could not be enough to break the trust relationship.

Ways in which employers can make use of polygraph tests

The Courts' primary objection to polygraph tests is that they are not an exact science. They are seen to be subjective interpretations of sets of data. In fact, in the case of FAWU obo Kapesi and Others v Premier Foods t/a Blue Ribbon Salt River (2012) 33 ILJ 1779 (LAC), Basson J stated that "at best a polygraph could be used as part of the investigative process to determine whether or not a further investigation into the conduct of a particular individual is warranted".

To supplement the polygraph results and make them useful as evidence, an employer would need to introduce expert evidence to 'establish the technical integrity of the process'. This does not mean that any person who conducts a polygraph test is qualified to testify in this regard. The expert evidence needs to be led by somebody who has the requisite independence and appropriate credentials in this regard.

Employers are encouraged to avoid sole reliance on the results of polygraph tests when dealing with investigations and disciplinary proceedings. If, however, the only method of reaching a conclusive end is by way of a polygraph test, then employers should ensure both that it is conclusive and that the circumstantial polygraph results are supplemented with the requisite expert evidence.