THE MULTI-CHANNELED POLYGRAPH - THE BASIC DESIGN
The standard modern polygraph has the same basic components:
(1) The Pneumograph –
This device consists of two tubes full of air, which are fitted around the subject’s chest and abdomen; the expansion and contraction of the tubes is recorded as the subject inhales and exhales in order to determine their rate and depth of breath.1
(2) The Galvanometers –
According to Stan Abrams' The Complete Polygraph Handbook, it is “[t]he skin’s resistance to electricity is measure through the use of two electrodes which generally are attached to the finger tips of the index and ring fingers”2
(3) The Blood Pressure Cuff Assembly –
This part can also be called the “cardiograph,” and it is a inflatable band of cloth which is attached to the upper arm in order to monitor blood pressure as the air which is pumped in the cuff is released proportionate to the amount of blood being pumped through the main artery of the arm; it can also determine the pulse rate of the individual 3
The technology of the modern lie detector only gathers the data from the different physiological monitors; it is the job of the examiner, or computer software, to interpret these changes in order to determine whether the subject is being truthful. When Keeler developed his polygraph in the 1930s, he also began the first school for teaching polygraph examiners.4 As Marston wrote in 1938, “it is a scientific test in the hands of an expert which does the lie detecting.”5 This importance given to the examiner has instigated the development of new and improved methods of interrogation, beginning with the word association test developed in the 1800s. Larson reintroduced this test briefly during his trials, as noted by Stan Abrams in his book, “by inserting a word associated with the criminal act at every third word,” before switching to an alternation between direct and indirect questions to compare reactions.6 In his book, Abrams also discusses Keeler's methods, particularyly a test called the guilty knowledge or peak of tension test (POT) or I/R (Irrelevant/ Relevant) test, which consisted of a “comparison of responses that included a number of non-significant items and a question that related to the crime.”7
The last test used primarily in the use of the polygraph is the Control Question Test (CQT), which is, according to the authors of Psychology and Law: Truthfulness, Accuracy and Credibility, “based on the assumption that control questions will generate more arousal than the relevant questions in the innocent suspect,” so answers to control questions and more direct questions related to the crime are compared for determinations of truth.8 The operator, or examiner, of the polygraph is the fifth component of this system of technology, which includes both the equipment itself: the pneumograph tubes, the blood pressure cuff, the galvanometers, as well as the design of the questions used in the interrogation.
This device consists of two tubes full of air, which are fitted around the subject’s chest and abdomen; the expansion and contraction of the tubes is recorded as the subject inhales and exhales in order to determine their rate and depth of breath.1
(2) The Galvanometers –
According to Stan Abrams' The Complete Polygraph Handbook, it is “[t]he skin’s resistance to electricity is measure through the use of two electrodes which generally are attached to the finger tips of the index and ring fingers”2
(3) The Blood Pressure Cuff Assembly –
This part can also be called the “cardiograph,” and it is a inflatable band of cloth which is attached to the upper arm in order to monitor blood pressure as the air which is pumped in the cuff is released proportionate to the amount of blood being pumped through the main artery of the arm; it can also determine the pulse rate of the individual 3
The technology of the modern lie detector only gathers the data from the different physiological monitors; it is the job of the examiner, or computer software, to interpret these changes in order to determine whether the subject is being truthful. When Keeler developed his polygraph in the 1930s, he also began the first school for teaching polygraph examiners.4 As Marston wrote in 1938, “it is a scientific test in the hands of an expert which does the lie detecting.”5 This importance given to the examiner has instigated the development of new and improved methods of interrogation, beginning with the word association test developed in the 1800s. Larson reintroduced this test briefly during his trials, as noted by Stan Abrams in his book, “by inserting a word associated with the criminal act at every third word,” before switching to an alternation between direct and indirect questions to compare reactions.6 In his book, Abrams also discusses Keeler's methods, particularyly a test called the guilty knowledge or peak of tension test (POT) or I/R (Irrelevant/ Relevant) test, which consisted of a “comparison of responses that included a number of non-significant items and a question that related to the crime.”7
The last test used primarily in the use of the polygraph is the Control Question Test (CQT), which is, according to the authors of Psychology and Law: Truthfulness, Accuracy and Credibility, “based on the assumption that control questions will generate more arousal than the relevant questions in the innocent suspect,” so answers to control questions and more direct questions related to the crime are compared for determinations of truth.8 The operator, or examiner, of the polygraph is the fifth component of this system of technology, which includes both the equipment itself: the pneumograph tubes, the blood pressure cuff, the galvanometers, as well as the design of the questions used in the interrogation.