inferences from indications of deception, it is necessary to make one additional assumption: that a person who is deceptive about certain undesirable past acts is at risk for committing different kinds of undesirable acts in the future.8

Some polygraph test situations, which can be described as focused screening situations, do not fit neatly into the above three categories because they have attributes of both the screening and the specific-incident investigation purposes. An example might be the investigation of a fairly large group of individuals who are suspected of involvement with a known terrorist organization. Such investigations are like typical screening situations in that there is no known specific incident that can be the focus of questioning, but they are like specific-event investigations if it is possible to ask specific questions about the organization, its leaders, or the places in which it operates. Strong physiological responses to such specific questions might indicate that the examinee has information about the terrorist organization and should be investigated more fully regarding possible ties to it. If the answers to such questions are likely to be known only to the investigators and to the organization’s members and close associates, the situation is amenable to the use of tests of the concealed information type, which are not otherwise considered to be applicable to screening situations.

The ability of polygraph testing to uncover the deceptions of interest and to serve broader law enforcement or national security goals may depend on the purpose of the test and the kinds of acts that are the subject of the relevant questions. It is plausible that the task of the polygraph is easiest in event-specific investigation and hardest in preemployment screening. The possibility that accuracy depends on the purpose of the test makes it unwise to assume that accuracy estimates calculated from data when the polygraph is used for one purpose are pertinent to its use for a different purpose.

Our study focused on the use of polygraph examinations for employee and preemployment screening. However, one of the critical limitations of the available research is the extreme paucity of studies that directly address the validity of the polygraph for current or preemployment screening. Most of the scientific research considered in this report deals with the use of the polygraph for event-specific investigations. Unfortunately, the relevance of such research for the screening context is not self-evident. As we note in Chapter 2, the sorts of decisions made in screening contexts (e.g., a forecast of whether a job applicant might pose a future risk) and event-specific investigations (e.g., an assessment of whether a suspect is truthful when denying a crime) are so fundamentally different that even the best event-specific research may not be relevant to the validity of the polygraph for employee or preemployment screening.

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