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NCJ Number: NCJ 131528     Find in a Library
Title: Validity and Reliability of Polygraph Decisions in Real Cases
Author(s): N Ansley
  Journal: Polygraph  Volume:19  Issue:3  Dated:(1990)  Pages:169-181
Date Published: 1990
Page Count: 13
  Annotation: A report on validity from all studies of real cases, conducted since 1980, is presented.
Abstract: Examiner decisions in these studies were compared to other results such as confessions, evidence, and judicial disposition. The 10 studies reviewed considered the outcome of 2,042 cases, and the results, assuming that every disagreement was a polygraph error, indicate a validity of 98 percent. For deceptive cases, the validity was also 98 percent, and for non-deceptive cases, 97 percent. The studies were from police and private cases; used a variety of polygraph techniques; and were conducted in the United States, Canada, Israel, Japan, and Poland. A report on all the studies of the reliability of blind chart analyses from real cases conducted since 1980 is also presented. Blind analyses of polygraph charts is not a complete measure of reliability, despite frequent misrepresentations. It is, however, related to reliability and validity. True reliability studies involve retesting, and there are no such studies involving real cases. The 11 studies of blind chart analyses included 922 cases, of which 828 were correctly decided. The confirmed deceptive cases were correctly decided at 94 percent; the non-deceptive at 89 percent. The charts were from police and private cases with numerical and global scoring and a variety of polygraph techniques. Four of the studies involved analyses of examiners' decisions and the decisions of blind evaluators. Based on 320 police and private cases, examiners were correct in 313 (98 percent); blind evaluators in 227 or 95 percent. Examiners and evaluators were both at 98 percent accuracy with deceptive cases, but differed considerably in truthful cases. Examiners were correct in 97 percent of the non-deceptive cases while blind evaluators were correct in 89 percent. These studies, which represent all that are available in the last decade, suggest that polygraph testing is highly accurate although an imperfect technique for detecting deception and verifying truth. 5 tables and 27 references (Author abstract)
Main Term(s): Polygraph techniques ; Polygraph reliability
Index Term(s): Evidence collection ; US/foreign comparisons
Type: Research (Applied/Empirical)
Country: United States of America
Language: English
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