Every situation in which polygraph testing might be contemplated, including each security screening situation, has its own characteristics in terms of the types and magnitudes of the costs and benefits presented by polygraph testing. These costs and benefits are of many types, some of which are impossible to estimate quantitatively with available knowledge. The choices should therefore be evaluated for each application on the basis of the characteristics of that application, available scientific knowledge about the test’s performance, and informed judgments about the values at stake. We have carefully examined the situation of employee security screening at the DOE laboratories, and the conclusions below apply to that situation. They are likely also to apply to other situations in which the base rates of the target transgressions are extremely low, the costs of false negative results can be very high, and the costs associated with using a screening procedure that produces a large number of false positive results would be very high.

Limitations for Detection The polygraph as currently used has extremely serious limitations for use in security screening to identify security risks and to clear valued employees. In populations with extremely low base rates of major security violations, such an application requires greater accuracy than polygraph testing achieves. In addition, there is a realistic possibility that the polygraph might be defeated with countermeasures, at least by the most serious security violators. The potential that a polygraph policy may deter security threats and elicit admissions and confessions may justify using the polygraph in security screening, but this rationale does not rest on the validity of the polygraph for psychophysiological detection of deception. Rather, it rests on the expectation that examinees’ behavior will be shaped by their concerns that they may be judged (rightly or wrongly) to be deceptive on the polygraph. Because of these limitations, even if the polygraph has some accuracy in actual field use, it does not follow that it should be used for screening because of the potential costs of such use, including the possibilities that it will lower morale and productivity in national security organizations and deter people with scarce and highly valuable skills from working, or continuing to work, in these organizations.

False Positives with “Suspicious” Thresholds Polygraph screening protocols that can identify a large fraction of serious security violators can be expected to incorrectly implicate at least hundreds, and perhaps thousands, of innocent employees for each spy or other serious security violator correctly identified. Given the range of scientifically plausible accuracy levels for poly-