Over time, there has, to some degree, been conflicting law regarding the extent of the admissibility of polygraph test results in disciplinary hearings.  More especially, this has related to whether an employer can rely solely on a failed polygraph test to prove the guilt of an employee on the balance of probabilities.

Employers are all too frequently of the mistaken impression that a failed polygraph test is quite enough to prove guilt; not so say our courts.

The recent Labour Court matter of Mustek v Tsabadi and others (case no. JR 2732/2010: Judgment day 2 March 2013) reiterates and reconfirms the extent to which polygraph test results may be utilised to prove guilt in disciplinary hearings.

In this case, eight laptop computers went missing from the employer’s premises.  The employer elected to administer polygraph tests in regards all employees who had access to the area from which the laptop computers had gone missing.  Four of the sixty-seven employees tested failed for the polygraph test, and were dismissed based on this evidence alone.

Judgment in this case emphasised certain important factors to be taken into consideration regarding the admissibility and extent to which polygraph test results may be utilised in disciplinary hearings.  The Court held that “our Courts have approached the use of polygraph tests with much circumspection, and it is now accepted that the result of a properly conducted polygraph is evidence in corroboration of the employer’s evidence and may be taken into account as a factor in assessing the credibility of a witness and in assessing the probabilities”.

It became apparent that in a separate arbitration hearing at the CCMA, another commissioner had in fact condoned the admissibility of the polygraph tests alone, and admitted this as sufficient evidence to prove guilt on the balance of probabilities.  In the Labour Court judgment, the judge however noted that commissioners are not bound to follow awards of fellow commissioners, even if two separate arbitration hearings are faced with the same facts.

More especially, it was held that “it is factious to suggest that one commissioner should complacently endorse the finding of another commissioner were the two matters have their origins in the same incident.  The rationale for the first commissioner’s decision has to be analysed.  There can be any number of reasons why that commissioner arrived at the conclusion he did.  To argue that a commissioner is bound by the findings of another commissioner is repugnant to the rules of precedent”.

The judgment continued that in essence, polygraph test results are indeed admissible, in disciplinary hearings, only insofar as they corroborate or support more direct evidence.  It is quite clear that our law has established a now well established precedent that if the only evidence leveled against an employee is a failed polygraph test, it will never be sufficient proof in its own right to prove that the employee is guilty on the balance of probability.  That is not to say of course that polygraph test results are inadmissible.  On the contrary, they are.  However, insofar as polygraph tests ought to be admitted in a disciplinary hearing, and indeed an arbitration hearing, such failed polygraph test results are only of value to the extent that, and insofar as they do, support more direct evidence introduced during the disciplinary or arbitration hearing.

When all is said, and done, polygraph test results have value as corroborating evidence only, and will never be sufficient as free standing evidence, to prove a case on a balance of probabilities.