Polygraph tests a wobbly foundation

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Tony Healy

Polygraph tests, or their equivalent, have been with us for quite some time.

During the Middle Ages in Europe, torture was a practice that was rooted in the theory that “the body’s agony would oblige the lying mind to croak out its secret”.

Over time, polygraph tests have been used for various purposes in various environments, including the workplace.

Existent case law on the value of polygraph results has been clear for quite some time.

If the only evidence an employer has against an employee is a “failed” polygraph test, the result will never be enough to prove the guilt of the employee.

Polygraph test results, at worst for an employee, produce a “deception indicated” result; they do not prove guilt in regard to the allegations made.

At most, such a polygraph test result may be introduced as corroborative evidence supporting direct or other more valuable evidence.

SA labour courts have always approached the admissibility of polygraph test results as proof of guilt with caution.

In Sosiba and others v Ceramic Tile Market (CCMA Arbitration 2001) it was highlighted that this cautious approach is necessary due to the fact that:

1. The person administering the test, while an expert on the handling of polygraph equipment, was neither a qualified doctor nor a psychologist.

2. The tests are simply an indicator of deception, and do not provide details of the extent of the misconduct, which is essential in the assessment of the sanction.

In Truworths v CCMA, case No JR789/07, the court held that “a polygraph test on its own cannot be used to determine the guilt of an employee. (See also John Grogan Workplace Law 9th edition page 160.)

However, a polygraph certainly may be taken into account where other supporting evidence is available.

There must also be clear evidence on the qualifications of the polygraphist and it should be clear from the evidence that the test was done according to acceptable and recognisable standards.

At the very least, the result of a properly conducted polygraph test is evidence in corroboration of the employer’s other evidence and may be taken into account as a factor in assessing the credibility of a witness and in assessing the probabilities of guilt and innocence in the case.

The mere fact that an employee, however, refuses to undergo a polygraph test is not in itself sufficient to substantiate an employee’s guilt.

In May 2010, the Labour Court in Fawu obo Kapesi and 31 others v Premier Foods Ltd (case No C640/07) held that … “It was clear from the evidence that researchers in the field of polygraph testing are not in unanimous agreement about the scientific status of the polygraph, particularly as far as the overall accuracy and usefulness of the test in detecting truthfulness or deception.”

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