Polygraph and the Law
For a polygraph examination to be legal, the subject must agree to participate in the process. Not only would an involuntary examination violate the right of the subject, but would produce psychological and physiological side effects that would cause the results of the examination to be inconclusive.
The polygraph test is only an aid to an investigation and cannot generally be utilised in court to legally establish absolute innocence or guilt.
The results of the examination – the expert opinion of the examiner as to the interpretation of the graphs produced by the subject are normally not admissible in either civil or military courts as evidence bearing on the issue of the guilt or innocence of the accused. However, legally obtained statement, admission or confession resulting from a polygraph examination is admissible as evidence and the examiner may testify in court as to the voluntariness of such evidence.
In South Africa Polygraphists have been accepted as expert witnesses by the CCMA where evidence needed to be tested for reliability. The duty of the commissioner is to determine the admissibility and reliability of the evidence. Polygraph tests may not be interpreted as implying guilt but may be regarded as an aggravating factor especially where there is other evidence of misconduct.
