area in which DNA profiling is least certain, laboratory error, is the area in which courts have had the most difficulty in deciding how to handle the uncertainty.)

The accuracy of polygraph testing does not come anywhere near what DNA analysis can achieve. Nevertheless, polygraph researchers have produced considerable data concerning polygraph validity (see Chapters 4 and 5). However, most of this research is laboratory research, so that the generalizability of the research to field settings remains uncertain. The field studies that have been carried out also have serious limitations (see Chapter 4). Moreover, there is virtually no standardization of protocols; the polygraph tests conducted in the field depend greatly on the presumed skill of individual examiners. Thus, even if laboratory-based estimates of criterion validity are accurate, the implications for any particular field polygraph test are uncertain. Without the further development of standardized polygraph testing techniques, the gulf between laboratory validity studies and inferences about field polygraph tests will remain wide.

The ambiguity surrounding the validity of field polygraphs is complicated still further by the structure of polygraph testing. Because in practice the polygraph is used as a combination of lie detector and interrogation prop, the examiner typically is privy to information regarding the examinee. While this knowledge is invaluable for questioning, it also might lead to examiner expectancies that could affect the dynamic of the polygraph testing situation or the interpretation of the test’s outcome. Thus, high validity for laboratory testing might again not be indicative of the validity of polygraphs given in the field.

Context of Polygraph Testing

The usefulness of polygraph test results depends on the context of the test and the consequences that follow its use. Validity is not something that courts can assess in a vacuum. The wisdom of applying any science depends on both the test itself and the application contemplated. A forensic tool’s usefulness depends on the specific nature of the test (i.e., in what situation might it apply?), the import or relevance of the test (i.e., what inferences follow from “failing” or “passing” the test?), the consequences that follow the test’s administration (e.g., denial of employment, discharge, criminal prosecution), and the objective of the test (lie detection or interrogation).

A principal consideration in the applied sciences concerns the content of a test: what it does, or can be designed to, test. Concealed information polygraph tests, for example, have limited usefulness as a screening device simply because examiners usually cannot create specific questions

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement