Requirements for a Valid Polygraph Test


There are certain prerequisites that should be kept in mind when determining whether a polygraph examination is valid. This is of particular importance when considering the use of polygraph results as evidence. The following are minimum requirements for the acceptability of a polygraph in a disciplinary hearing, the CCMA or in court:

The Polygraphist

  1. The polygraphist must have been trained at a polygraph training facility accredited by the Southern African Polygraph Federation. This implies adherence to a strict code of conduct and ethics.
  2. The polygraphist must be a member in good standing at the Polygraph Association of South Africa.
  3. The polygraphist must be experienced enough to be able to analyse the chart tracings or polygrams and such experience must have been gathered while working under supervision.
  4. The polygraphist must be independent, impartial and objective.
  5. The polygraph technique and test procedure must be explained to the examinee.
  6. Polygrams or chart tracings must be assessed manually and computerised evaluation may be used only for the purpose of quality control or to obtain other opinions.
  7. The polygraphist must be able and willing to testify as an expert witness.

The Examinee

  1. The examination must be done voluntarily and this must be stated in writing.
  2. The examinee must be, as far as can be ascertained, free of serious illness.
  3. The examinee should preferably, not have been subjected to accusatory interrogation prior to the examination.
  4. The examinee must not be under the influence of alcohol or narcotics at the time of the examination.
  5. The examinee must have had a reasonable amount of rest prior to the examination.
  6. The examinee must have been prepared and notified in advance about the examination.

The Polygraph Instrument

  1. The instrument must be properly calibrated according to manufacturer’s specifications.
  2. The instrument must be in good working order and record at least three channels.
  3. At a minimum, the device should record tracings for cardiovascular and breathing patterns as well as galvanic skin responses.

The Polygraph Technique

  1. An internationally accepted, valid questioning technique must be used.
  2. All questions must be thoroughly reviewed with the examinee before the collection of charts takes place.
  3. A minimum of three polygraph charts should be recorded during the chart collection phase of the examination.
  4. The environment in which the examination is administered should be conducive to proper polygraph testing, i.e. a quiet environment without serious visual or audio interference.