In this series on the polygraph, I'm reviewing some of the applications and issues of interest to security personnel considering polygraphs as a tool for pre-employment screening and in investigations of possible in-house computer crimes. Today, I'll look at the reliability of polygraph testing.

The most significant study of the reliability of polygraph testing was carried out by a distinguished panel of scientists convened under the auspices of the National Research Council of the National Academies of Sciences (NAS) of the United States. Published in 2003, it is The Polygraph and Lie Detection, which I cited in part 1 of this series. An anonymous writer for Government Executive wrote:

“The polygraph has proved to be a questionable indicator… [T]he National Academy of Sciences… noted the danger of incorrectly implicating innocent staffers and suggested that testing would lower morale and productivity and deter people with scarce and valuable skills from working in organizations that use it.” The same author pointed out that the Department of Energy stopped using the polygraph in pre-employment screening at the end of September 2006 “for general screening of applicants for employment and incumbent employees without specific cause.”

The Executive Summary of the NAS report includes this warning:

"For employee screening, there is no specific event being investigated, and the questions must be generic (e.g., 'Did you ever reveal classified information to an unauthorized person?'). Both examinee and examiner may have difficulty knowing whether an answer to such a question is truthful unless there are clear and consistent criteria that specify what activities justify a 'yes' answer. Examinees may believe they are lying when providing factually truthful responses, or vice versa. Polygraph tests might elicit admissions to acts not central to the intent of the question and these answers might be judged either as successes or failures of the test. In this regard, we have seen no indication of a clear and stable agreement on criteria for judging answers to security screening polygraph questions in any agency using them.

"The use of polygraph testing for preemployment screening is even more complicated because it involves inferences about future behavior on the basis of information about past behaviors that may be quite different (e.g., does past use of illegal drugs, or lying about such use on a polygraph test, predict future spying?)."

M. E. Kabay, PhD, CISSP-ISSMP, specializes in security and operations management consulting services. CV online.