The recorded differences and purported indicia of deception may be caused by numerous variables. These unassessable factors are crucial to an accurate polygraph examination. Among the proven variables are: (1) physical characteristics of the subject such as fatigue, obesity, heart disease, respiratory difficulties and abnormal blood pressure; (2) temporary or permanent mental disorders such as delusions, feeble-mindedness or insanity, which result in an inability to affirmatively participate or to be unable to differentiate between right and wrong; (3) the undetected use of alcohol or drugs; (4) distractions in the examination setting, such as extraneous noises, temperature fluctuations, or unusual objects; (5) the responses to his/her own lying; (7) a guilty party's subjective belief in his/her own innocence; (8) excessive previous interrogation; (9) prior dry run examinations leading to belief that one can beat the machine; (1) the complexity of the matters being investigated; (11) the wording of the relevant questions; (12) the extent of motivation and fear by the subject that the polygraph will detect his/her lying; and even (13) the nervousness of an innocent subject induced by fear or a guilty complex involving a different offense.
This is archived content from the U.S. Department of Justice website. The information here may be outdated and links may no longer function. Please contact firstname.lastname@example.org if you have any questions about the archive site.
261. Polygraphs—Examination Variables
Updated January 22, 2020