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The use of polygraph tests in the workplace has always been controversial. These tests involve the measuring of a person’s physical responses (like blood pressure and perspiration) when answering various questions and are relied upon to indicate deception.

Faced with dishonesty, and especially theft, lie detector tests can seem to offer a “quick-fix” solution - an almost magical process promising to lay bare the souls of one’s employees. However, employees are understandably wary of having their secrets stripped down for all to see.

Our labour dispute resolution tribunals have recently again considered the use of these tests in the workplace.

In the case of MEWUSA obo Mbonambi and S Bruce CC, an employee was dismissed after being found guilty of stealing money and a cellphone. He was the only one of eleven employees polygraph tested whose answers indicated “deception”.

The arbitrator affirmed the approach taken by previous tribunals; i.e. that the outcome of polygraph tests may be taken into account when there are also other grounds for believing that the employee has been dishonest.

In this case, the other grounds were: that another witness placed the employee at the scene of the theft at the relevant time; and that the arbitrator found the employee’s evidence to be both inconsistent and dishonest. In these circumstances, the corroborating evidence of the polygraph test was found to be relevant. On a balance of probabilities, the employee was held responsible for the theft.

In another case, Numsa obo Mkhonza & Others and Assmang Chrome Machadodorp Works, greater weight was given to the results of the polygraph tests than in the above case.

Here, five employees claimed they had been unfairly dismissed after copper pads disappeared from the company stores where they all worked. Sixty-five employees were subjected to a polygraph test by a qualified examiner. Only the five aggrieved employees proved to be deceptive. They were dismissed.

Although the polygraph results apparently did not conclusively indicate that the dismissed employees committed the theft, the arbitrator emphasized that the dismissals were for “suspected collusion, involvement or …… even knowledge that some mischief was at play” and that “the employees deliberately ….. failed to bring this to management’s attention and …. breached their duty to act in the employer’s best interests”.

Apart from the polygraph tests, the arbitrator was apparently persuaded there was other evidence linking them to the theft. This does not seem to have amounted to more than that the employees had the means and knowledge to commit the misconduct. It seems rather a leap to conclude that this constitutes separate evidence of misconduct. It would be prudent to assume that this approach would not necessarily be followed in other matters.

The recent case law then would seem to support the continued use of polygraph testing as an investigative tool for employers faced with dishonesty, as well as having a limited and supportive evidentiary role to play in disciplinary hearings. However, certain points must be kept in mind if these tests are to be used:

Tests should be conducted by a qualified person using accepted procedures;

  • Employees’ consent is needed;
  • Employees should be physically and mentally fit;
  • The process and reasons for the tests should be fully explained to participating employees;
  • If the polygraph results are to be used as evidence, the qualified examiner must himself give evidence and must explain the import of the results.
  • If an employee refuses to submit to a polygraph test, it is unlikely to be fair to insist on it, although a refusal could give rise to an adverse inference about the motives for refusing. If warranted in a particular business, it may be useful to include an agreement to submit to polygraph testing in all employees’ contracts of employment at the time of engagement.

    Written by Helena Janisch for

    Labourwise is an on-line labour relations service aimed at assisting SMMEs with the implementation of effective labour relations. They can be contacted via or

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