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  » Appendix XVIII
Warren Commission Report: Page 813« Previous | Next »

(APPENDIX XVII - Polygraph Examination of Jack Ruby)

Q. Did "Blackie" Hanson speak to you just before you shot Oswald?


A. No.88

INTERPRETATION OF THE TEST

A polygraph examination is designed to detect physiological responses to stimuli in a carefully controlled interrogation. Such responses may accompany and indicate deception.89 The polygraph instrument derives its name from the Greek derivative "poly" meaning many and the word "graph" meaning writings.90 The polygraph chart writings consist of. three separate markings placed on a graph reflecting three separate physiological reactions.91 A rubber tube is placed around the subject's chest to record his breathing pattern on a pneumograph.92 That device records the respiratory ratio of inhalation and exhalation strokes.93 The second component is called a galvanic skin response which consists of electrodes placed on the examinee's fingers, through which a small amount of electrical current is passed to the skin.94 The galvanometer records the minute changes in electrical skin response.95 The third component consists of a cardiograph which is a tracing obtained by attaching a pneumatic cuff around the left arm in a manner very. similar to an apparatus which takes blood pressure.96 When the cuff is inflated, that device records relative blood pressures or change in the heart rate.97


From those testing devices, it is possible to measure psychological or emotional stress.98 This testing device is the product of observation by psychologists and physiologists who noted certain physiological responses when people lie.99 In about 1920 law enforcement officials with psychological and physiological training initiated the development of the instrument to serve as an investigative aid.100


The polygraph may record responses indicative of deception, lint it must be carefully interpreted.101 The relevant questions, as to which the interrogator is seeking to determine whether the subject is falsifying, are compared with control questions where the examiner obtains a known indication of deception or some expected emotional response.102 In evaluating the polygraph, due consideration must be given to the fact that a physiological response may be caused by factors other than deception, such as fear, anxiety, nervousness, dislike, and other emotions.103 There are no valid statistics as to the reliability of the poly-graph. 104 FBI Agent Herndon testified that, notwithstanding the absence of percentage indicators of reliability, an informed judgment may be obtained from a well-qualified examiner on the indications of deception in a normal person under appropriate standards of administration.105


Ordinarily during a polygraph examination only the examiner and the examinee are present.106 It is the practice of the FBI, however, to have a second agent present to take notes.107 lt is normally undesirable to have other people present during the polygraph examina-

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