Polygraph tests, commonly known as lie detector tests, measure physiological responses such as heart rate, blood pressure, respiration, and perspiration while a person answers questions. The goal is to detect signs of stress or deception. The examiner compares responses to baseline or “control” questions with those relating to the matter under investigation. However, the reliability of polygraph tests remains controversial. Results are not infallible and are often challenged due to their scientific and legal limitations.

When Are Polygraph Tests Used in the Workplace?

Employers may consider using polygraph testing in the following contexts:

  • Investigating Misconduct or Theft – Polygraphs are sometimes used when employers suspect dishonesty, theft, fraud, or other serious workplace misconduct.
  • Pre-Employment Screening – Some employers may use polygraphs during recruitment processes—especially in high-risk roles, though this is controversial and not widely practiced in South Africa.
  • Security-Sensitive Roles – In industries such as law enforcement, private security, or intelligence services, polygraph testing may be used to assess candidates’ trustworthiness.

Legal Concerns and Implications under South African Labour Law

Voluntary Consent, Right to Privacy, and Compliance with the Protection of Personal Information Act (POPIA)

The Constitution protects employees’ right to privacy. Polygraph testing can infringe on this right if done without voluntary, informed, and written consent. Forcing or coercing an employee to undergo a polygraph may be unlawful, and any disciplinary action based solely on such a test could be considered substantively and procedurally unfair. Polygraph tests may involve the collection of personal and special personal information, which must be handled lawfully and securely in terms of POPIA. Consent and data protection practices must be aligned with the Act.

Lack of Clear Legal Framework

South African labour legislation does not specifically regulate the use of polygraphs. As a result, employers must proceed with caution, as there is no statute-based authority for their use.

Evidentiary Weight and Admissibility

Polygraph results are generally not admissible as conclusive proof of guilt or dishonesty at the CCMA or Labour Court. Their hearsay nature, questionable accuracy, and the need for expert interpretation mean they carry limited probative value unless supported by corroborating evidence.

Risk of Unfair Dismissal

Relying solely on polygraph results for disciplinary action or dismissal carries a high risk of unfair dismissal claims. Employers should ensure that there is independent, corroborating evidence before taking any adverse action.

Relevant Case Studies:

Several decisions from the CCMA, Labour Court, and Labour Appeal Court (LAC) underscore the limited value of polygraph evidence. For example, in NUMSA obo Ntobeng and Others v Witbank Foundry and Others (2008), the commissioner ruled that dismissal based solely on a failed polygraph was unfair. The test’s results were considered unreliable hearsay, especially since the examiner was not called to testify. In SACCAWU obo Khakhatiba v Country Meat Market (Pty) Ltd (2008), the CCMA held that polygraph evidence alone was insufficient for dismissal and ordered reinstatement with full back pay. In DHL Supply Chain (Pty) Ltd v De Beer NO & Others [2014] ZALAC 18, the Labour Appeal Court confirmed that a failed polygraph test is not enough to prove dishonesty. The employer bears the burden of presenting expert evidence to validate the test’s reliability. Finally, in Goldplat Recovery (Pty) Ltd v CCMA & Others (2021), an employee was dismissed after being the only person to fail a polygraph test during a theft investigation. The CCMA found no direct evidence of wrongdoing and ruled the dismissal unfair, awarding maximum compensation.

Conclusion:

While polygraph tests may be used in the workplace to investigate misconduct or assess trustworthiness, they must be approached with caution under South African labour law, as there is no specific legislation regulating their use. Moreover, should employers consider utilizing polygraph tests in the workplace, it is vital that this occurs in a legally compliant manner, as employees must give informed, written, and voluntary consent, and all data collected must comply with POPIA. Employers should also be cautious to rely solely on polygraph results without additional corroborative evidence, or to base their dismissals on failed polygraphs, as these dismissals are frequently overturned as unfair, and our forums have made it clear that polygraph results are not definitive proof of misconduct and are viewed with scepticism. Polygraph testing should form only one part of a broader investigation, not the sole basis for disciplinary action or dismissal.