POLYGRAPH TESTING IN THE WORKPLACE
- EOHCB National
- Oct 2
- 4 min read

A polygraph test, often called a ‘Lie Detector Test, is a popular tool for employers seeking to verify a person’s truthfulness, investigate misconduct, or manage risk in sensitive roles. But its use is not without legal and ethical constraints.
While polygraph testing can be a useful investigative tool, employers must tread carefully and remember that general labour principles will apply.
The evidentiary Value of polygraph tests
Polygraph tests indicate whether the subject has answered the questions truthfully but are not regarded as being 100% accurate therefore polygraph results are not regarded as definitive proof of guilt in a disciplinary hearing.
Chairpersons and commissioners will always assess the reliability and admissibility of polygraph results alongside other facts therefore they may be used supporting evidence but the results cannot be used as a standalone justification for dismissal.
In other words, polygraph test results, on their own, are not a basis for proving that someone committed an act or omission as alleged by the employer but may be used as a factor in determining the probabilities.
Supporting Case law:
The controversy surrounding polygraph tests and the reliability of same has for some time been a topic of debate in our judicial system. Because polygraph tests are regarded as not being entirely reliable, dismissals based solely on the result of a polygraph test have generally been found to be unfair.
In the case of Amalgamated Pharmaceuticals Ltd v Grobler NO and others the third, fourth and fifth respondents were dismissed for misappropriation of company property. A polygraph test showed that they could be responsible for the serious stock losses suffered by the applicant. The Labour Court agreed with the reasoning of the Commissioner who found that, in practice, a polygraph does not serve to prove that someone is actually lying, for the questions are often too broad to exclude that which is neither intended nor sought. And it most definitely does not prove that someone is guilty. It is merely an indication of deception.
It has been widely accepted by the Labour Court and the CCMA in cases such as Sosibo & others and that, polygraph testing in the workplace is highly contentious and the admissibility of its results remains moot. The sole reliance by the employer on unspecific polygraph results is insufficient to discharge the onus in terms of section 192 of the Labour Relations Act 66 of 1995 to prove that the dismissal was fair. To discharge this onus, the test of a balance of probabilities is used. To only present polygraph evidence is not enough to show that the dismissal was fair because there is no corroborating evidence.
In NUMSA obo Ntobeng & others v Witbank Foundry & others – (2008) and SACCAWU obo Khakhatiba / Country Meat Market (Pty) Ltd (2008) the commissioner noted that the direct cause of the dismissal was the employee’s failure to pass the polygraph test. After reviewing case law on the admissibility of polygraph test results, the commissioner held that labour tribunals attach little weight to such evidence because polygraph test results intrude into an area that the commission is itself enjoined to decide; because they constitute hearsay or opinion; because deceit is used to obtain a response from the subject of the test; because such tests do not provide the full context of an answer and because they are not generally regarded as scientific. In short, more is needed than a polygraph test result to prove that an employee is guilty of misconduct. Furthermore, the person who administered the test had not been called to explain or verify the result. The dismissal was ruled substantively and procedurally unfair. The employee was reinstated with retrospective effect.
In a Labour Appeal Court case, DHL Supply Chain (Pty) Ltd v De Beer NO and Others (2014) 35 ILJ 2379. The Court made clear that the onus rests with the employer to lead expert evidence to prove the accuracy of the polygraph test.
A recent Labour Court case, Goldplat Recovery (Pty) LTD v Commission for Conciliation Mediation and Arbitration [2021] JOL 49890 (LC) has again dealt with a matter where an employee was dismissed solely based on the results of a polygraph test. An employee had been found in possession of gold. At his disciplinary hearing he argued that there was a gold smuggling syndicate and that he had no access to the restricted area in which the gold was kept. The company set their targets on anyone who had access to the restricted area and subjected most of the employees to a polygraph test. One employee was found to have failed the test and was dismissed. The employee referred an unfair dismissal dispute to the CCMA and the Commissioner found the dismissal to be unfair. The company took the award on review in the Labour Court. The Court held that the employer failed to call an expert witness to prove the validity of the polygraph test and failed to submit into evidence the other employees polygraph tests even though they had ‘passed’. The employer was ‘hopeless’ in their endeavour to prove that the dismissal was fair and dismissed him on mere suspicion.
Even if a provision in an employment contract which states that an employee could be dismissed solely on a negative polygraph test result exists, it can not be said to be fair. In a recent CCMA case, Mlangeni v Corporate Investigating and Veracity Assessments [2021] 3 BALR 264 (CCMA), a security guard was dismissed for allegedly stealing stock from a client. The company made him take a polygraph test and the result registered as deception. After refusing to sign a settlement agreement, the security guard claimed unfair dismissal while the company maintained that it was contractually entitled to terminate his employment. Thus, employers should be weary of solely relying on the results of polygraph tests.
In conclusion, polygraph test results, on their own, are not a basis for proving that someone committed an act or omission as alleged by the employer but may be used as a factor in determining the probabilities.
Polygraph testing should be part of a broader, fair process that respect employee’s rights.
