Voice Stress - Applications

Applications

The purpose of a VSA examination is to attempt to determine the truthfulness of responses made by an examinee regarding the subject under investigation. Determinations are made by analyzing and scoring the degree of voice stress on voice-grams produced by the examinee. Traditional analysis of voice grams was achieved by allocating "percentages of stress" ( % ) according to the patterns so produced.

High levels of voice stress may indicate that the examinee is deceptive as is the case with polygraph, though the polygraph uses multiple modalities. In respect of VSA, squared voice grams indicates less frequency in the uttered response; repetitive patterns presenting and thus higher stress whilst 'wave form' or 'domed' signatures indicate less stress. Manual scoring of old (obsolete) VSA systems is extremely difficult and often unreliable.

Questions may be posed to elicit simple "yes" or "no" answers, but can be posed to produce a narrative response. Questions are formulated for each individual being examined to compare situational stress signatures with Control Question and Relevant Question signatures, in order to identify (deceptive) 'stress signatures'.

Professional VSA instruction follows the polygraph model of PDD training and uses Backster and Reid question protocols. Any deviation from scientifically validated protocols renders the process to be unreliable. Question protocols containing >12 questions and multiple issues are invalid and unreliable.

It is of utmost importance that a VSA Instructor should have received APA grade PDD training AND Instructor certification from at least One polygraph manufacturer. Basic PDD training should be strictly observed and administered. Low standards of training produce poor examiners.

VSA technology together with validated testing protocols, is designed to protect the innocent and avoid 'false positive' results. VSA is designed to assist any investigation by establishing the veracity of a subject's verbal responses.

Devices used to analyze voice stress are usually used in the presence of the individual under investigation; however, they can also be used covertly, since all that is needed is a voice, a microphone or a tape recording.

There are no known physical countermeasures for VSA. Conversely according to Honts et al., the simple use of a 'tack' placed under the tongue of the examinee, to be used as a countermeasure, can reduce the accuracy of polygraph results from 98% to 26%.