According to the APA Polygraph Model Policy on Standards, there are some people who aren’t suitable for polygraph testing.They include minors, IQ-impaired individuals, and others. The list below should be regarded as advisory, with exceptions likely in extreme circumstances:
1. Age score
Generally individuals of 12 years or older may be asked to undergo a polygraph test. From a more technical point of view, however, only individuals with a Mean Age Equivalence or Standard Age Score of 12 years or older as determined through standardised psychometric testing are eligible for polygraph testing.
2. IQ score
Individuals with an IQ less than 55 or who suffer from severe mental retardation are deemed unsuitable for polygraph testing. Polygraph testing requires a firm comprehension of the difference between right and wrong as well as an ability to differentiate between truth and lies. The consequences of potentially deceptive behaviour should also be within the mental grasp of the individual for him or her to be considered eligible for polygraph testing.
Individuals who require 24/7 observation or assistance as a result of psychiatric or developmental conditions are deemed not suitable for polygraph testing. Similarly, individuals who are deemed to be disconnected from reality (psychosis) or who are suffering from a psychotic condition are also deemed ineligible.
Observable impairments of various natures may render an individual ineligible for polygraph testing. This includes impairment due to prescribed or non-prescribed controlled substances (including alcohol), and impairment as a result of sleep deprivation.
Extra criteria for eligibility
The following criteria do not form part of the APA Polygraph Model Policy on Standards, but are nevertheless regarded as accepted criteria for polygraph testing in South Africa.
Polygraph testing, at least in South Africa, has to be done completely voluntarily. The willingness of the examinee (the person to be tested) has to be demonstrated in writing.
6. Advanced notification
It is essential that an examinee receives a reasonable amount of rest prior to the examination – and that the examinee is notified of the examination prior to it taking place.
While not a specific criteria for ineligibility, it is strongly recommended that any examinee should not be subjected to accusatory interrogation prior to the polygraph examination.