Labour Law

Lie Detectors – Polygraph Tests

By 06/05/2015 June 9th, 2021 No Comments

The use of so-called lie detector or polygraph tests is slowly finding its way into disciplinary enquiries . This is bringing with it a host of legal problems especially relating to the admissibility of such tests as evidence. This paper attempts to answer some of the questions relating to the use of polygraph tests at disciplinary hearings.

How do they work?

Polygraph tests measure several physiological changes which take place when the subject is not telling the truth for example: changes in the subjects voice and skin conductivity. The principle behind it is that certain psychological states of mind will produce certain physiological responses e.g. sweaty palms. A polygraph test plots the physiological responses to certain questions, which must then be interpreted by the tester.

Are they accurate?

If calibrated properly and used by a properly trained person, the polygraph should prove to be fairly accurate. One of the reasons for this is that the machine takes several different factors into account. The problem lies in the fact that not everyone will exhibit the same “symptoms” when telling a lie. Just as some people are able to get away with lying to someone “face to face” so some people may be able to get away with lying to the machine.

The biggest doubt as to the machines accuracy however is that the physiological responses which it produces may not be brought about only by lying. As the tests are often administered under stressful conditions, many people have argued that the stress itself may bring on certain conditions in the body which may simulate those which arise when telling an untruth.

However the experts seem to agree that the biggest determinant will be the person who actually administers the test. The more experienced the tester, the more accurate the results will be.

Are they legal?

There is a difference between evidence which is admissible and that which is reliable. Just as a presiding officer has to be careful when accepting evidence from witnesses who may be unreliable, so too should he exercise caution when accepting polygraph results.

In criminal cases polygraph tests are not at all admissible. However in a disciplinary inquiry the rules of evidence are not as strict as they are in criminal proceedings. This means that lie detector tests can be used when dealing with employees and the results are admissible as evidence at disciplinary hearings. However this does not give any indication of how much weight should be attached to the results obtained from polygraph testing.

Generally polygraphs may be used as corroborating evidence that is they may be used to support or strengthen other, more concrete evidence. If used on their own, it is extremely unlikely that a court will attach very much weight to the results of a polygraph test.

How can they be used?

In order to illustrate this point, I will use the basic facts from a recent unreported case which are as follows: A business suffers a burglary overnight. From the police report it becomes apparent that there was a degree of inside involvement. The company therefore issues a statement that certain employees will be requested to undergo lie detector tests. The company then identifies all the employees who had access to the premises and informs them that they are to undergo polygraph testing. One employee (H) initially refuses but later agrees to take the test. He then fails the test on the questions relating to the burglary. He is offered a chance to undertake a second test on the understanding that should he pass, all charges would be dropped. H is unable to attend the session. At a later disciplinary hearing he cannot remember why he was not able to attend the second test. He is again offered the opportunity of taking a second test but simply makes excuses. Subsequent to the hearing, H is dismissed.

Now the question which must be answered is simply what conclusions can be drawn from these facts?

First of all it is important to note that any employment relationship is based on trust and when that trust breaks down, the relationship cannot continue. However an employer or employee must have reasonable grounds for showing that there has been a breakdown of trust. An employer cannot arbitrarily allege a breakdown of trust in order to effect a dismissal and if the dismissal is based on these grounds, the employer must show that the breakdown is due to the employees fault.

Secondly it is generally held that an employer is not justified in dismissing for a suspicion (or even a strong suspicion). However if the employee holds a position of trust, suspicion of dishonesty may cause this trust to be broken down, provided that the suspicions are based on reasonable grounds.

In this case H first of all refused to take the test and then subsequently failed on the questions relating to the burglary. This indicates that he knew something about it a suspicion that would cause the relationship of trust to be broken down fairly seriously. The second important fact is that when offered a chance to take a second test, he was not able to. This seems to create greater suspicion of his involvement.

This case illustrates the two applications of these tests: to show guilt or innocence. The first test was used as evidence of H’s guilt while the second test could have been used to show his innocence (had it given a result supporting this claim)

We should remember that no one ever has to “prove” their innocence but rather their accuser has to prove their guilt. With this in mind an employee who has nothing to hide and is accused with an offence such as this should view the lie detector as an opportunity to show that they are innocent. An interesting question which this poses is whether an employer would be able to draw an adverse inference from an employees refusal to take such a test.

As stated above, it is not generally acceptable to dismiss an employee because of a suspicion. However in the above case it was held that H’s initial refusal to take the test and subsequent failure created a strong enough suspicion as to his involvement in the burglary to have caused the trust relationship to break down, and his continued employment was therefore intolerable. His dismissal was held by the CCMA to be both procedurally and substantively fair.

Concluding Remarks

Many questions remain unanswered on this topic and until more judgements are made the use of lie detectors will remain a bit of a gray area in law. This being said, they are undoubtedly extremely useful in an employment relationship, as long as the user is aware of their limitations.

Ian McLaren

Ian Mc Laren

Ian Mc Laren

Ian McLaren BA LLB (WITS) General Educated St Johns College, Houghton. BA LLB University of the Witwatersrand 1984 Founded McLarens Attorneys September 1986. Right of Appearance High Court, October 1996. Expertise Litigation, Labour Law, Commercial Law, Family Law, Pension and Provident Funds, Customs and Excise, Wills, Deceased Estates, Trusts, Commercial Agreements, Reviewing and Drafting Government Legislation, Information Technology. Committees/ Trusts Law Society of South Africa Information Technology Committee. Trustee Verney College Educational Trust Other Transvaal Provincial colours for Practical Shooting. Third degree Black Belt JKS Karate. Photographer and motor cyclist Lectured for Continuing Legal Education on Information Technology issues.