Use of a Motion Chair in the Detection of Physical Countermeasures

• NCJ Number: 112834
• Journal: Polygraph Volume: 17 Issue: 1 Dated: (March 1988) Pages: 21-27
• Author(s): M Stephenson; G Barry
• Date Published: 1988
• Length: 7 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America
• Note: This article was previously published in the 'Canadian Association of Police Polygraphists Newsletter.'

Annotation

This study indicates that the motion chair is useful in identifying a polygraph examinee's attempt to distort a polygraph examination's outcome through subtle muscular movements.

Abstract

The motion chair contains a strain gauge, which is a pressure-sensitive or weight-sensitive recording device, typically less than the size of a dime, electronically activated and capable of having its sensitivity calibrated linearly. This device incorporates its own component and recording pen in the polygraph and records any change in pressure caused by examinee movement. The effectiveness of the motion chair was tested by using it with 12 subjects who had recently completed 10 weeks of a 12-week polygraph examiners course at the Canadian Police College. During the course of polygraph examinations, subjects were instructed to perform three physical countermeasures. Both the examiner and an observer were asked to watch for examinees' physical movements. Of the 33 scoreable physical countermeasures, 9 percent were identified by the examiner, 36 percent by the observer, and 85 percent by the motion chair. 2 tables.