Although the Polygraph is referred to as "A Lie Detector", the polygraph is not a lie detector in the sense of the word. A lie is spoken....it is a verbal communication of that which is not the truth. The polygraph does not monitor or record the voice. In a sense however the answer to a question is associated with responses that are monitored and recorded by the polygraph instrument. But no actual lie is recorded to determine truth or deception. There is in fact no instrument or device that can actually identify a lie or truth in the spoken word itself. The Polygraph is derived from two Greek words: Poly - meaning "Many" & Graph - meaning "writings". This refers to the more than one involuntary physiological parameter that the instrument monitors and records. To begin to understand what the polygraph does, one has to understand a bit about physiology. We have a built in emergency system. This system is completely involuntary and is controlled by the autonomous nervous system. The autonomous nervous system is what causes the changes to take place in our bodies when we feel threatened and identify danger. We are all accustomed to these changes and have experience them at one or other time in our lives. The next step is understanding why a person who has committed a crime or dishonest deed will lie when confronted about it. A person lies because there are consequences associated with being exposed. A person knows what they have done and understands that there are consequences in the event that they are exposed. It is a natural human behavioural pattern to try and protect one’s self and to avoid the consequences. The best way to do this when confronted is to lie. So telling a lie to the question is a way of protecting one’s self. Regardless of the reason, when one tries to protect one’s the autonomous nervous system responds, causing changes in the body. These changes are measurable and are recorded through the use of an instrument called a polygraph. If a guilty person is attached to polygraph and is asked questions about the crime / incident, they will lie to protect themselves from the consequences. Because they are trying to protect themselves the autonomous nervous system causes changes to take place, which are referred to as, deceptive responses. If the same questions are being asked to an innocent person, the person has nothing to protect themselves from. Therefore notable difference in a deceptive person’s responses and non-deceptive person responses can be seen.
The polygraph process consists of four sections:
Pre-test: In this time the Examiner will explain the polygraph and the physiology, the person rights, the case facts are discussed and a consent form is signed.
Test Phase: This is when the person is attached to the instrument, the questions are asked and the data is recorded. More than one chart is always run.
Chart analysis: The Examiner will analyze the data and conclude the outcome of the test. There are 4 possible outcomes.
Post-test: There are a number of variables that will determine this section of the test. The person will however be informed of their test result.
The final test results can be:
Deception Indicated - Person failed the test
No Deception Indicated - Person passed the test
Inconclusive - Unable to conclude a pass or fail result
No Opinion - This usually occurred when a person has been uncooperative during the test phase and the data has been corrupted.
It is VERY IMPORTANT to note that the Polygraph as an instrument does not determine the accuracy or validity of the test. The Polygraph instrument is just the recording device used during the process. It records measurable changes in the body. Therefore there is no accuracy or validity of the test results attached to the instrument. The accuracy and validity are based entirely on the competency of the Polygraph Examiner. It is therefore VERY IMPORTANT to only make use of Examiners who have received internationally recognized certified and accredited training.
Nervousness is a completely normal feeling that one will experience when having to undergo a polygraph test. Nervousness is a state that exists throughout the test. Nervousness does not cause deceptive responses....deception causes deceptive responses. One must understand that a Polygraph Examination is a controlled process in a suitable environment....and not an interrogation. The Examiner also has a duty to explain the entire testing process and the instrumentation to the person being tested. The Examiner must set the environment and place the person at ease. Innocent people tend to be cooperative and listen to the Examiner before the actual test. They are therefore able to set their own minds at ease about the process. For the guilty person, it does not matter, they are usually hoping that the polygraph does not work or they are trying to figure out a way of how to beat the test.
Polygraph examiners have been accepted as expert witnesses whose evidence needs to be tested for reliability. The duty of the Commissioner is to determine the admissibility and reliability of the evidence. Polygraph Test may not be interpreted as implying guilt but may be regarded as an aggravating factor especially where there is other evidence of misconduct. In other words, Polygraph Test results, on their own, are not a basis for a finding or guilt. It can be used only in support of other evidence.
It is against the Constitution of South Africa to compel a person to undergo a Polygraph examination, unless she or he consents to it. The consent must be in writing. The individual should be informed that:
The examinations are voluntary;
Only questions discussed prior to the examination will be used;
He/ she has a right to have an interpreter, if necessary;
Should he/she prefer, another person may be present during the examination, provided that person does not interfere in any way with the proceedings;
No abuse, in whatever way, will be allowed;
No discrimination with be allowed;
No threats will be allowed.
Generally, employers are permitted to use the polygraph to investigate specific incidents where –
Employees had access to the property which is the subject of the investigation;
There is a reasonable suspicion that the employee was involved in the incident;
There has been economic loss or injury to the employer’s business like theft of property;
The employer is combating dishonesty in positions of trust;
The employer is combating serious alcohol, illegal drugs or narcotics abuse and fraudulent behaviour within the company;
The employer is combating deliberate falsification of documents and lies regarding true identity of the people involved.
Although there is no evidence that it is dangerous for the unborn baby, our examiners will not conduct a polygraph test on any women who are pregnant or expect that she might be pregnant.