National security professionals have few scientifically valid methods for detecting deception in people who deny being involved in illicit activities relevant to national security. Numerous detecting deception studies have demonstrated that the Modified Cognitive Interviewing (MCI) method is one such method - yielding detecting deception rates (i.e. 80-85%) that are significantly above those achieved by chance (i.e. 50%) or by human judgments (i.e. 54-56%). To date, however, no MCI studies have involved dilemmas of ethological interest to national security professionals. This project begins to address this gap in the scientific literature. In it, we compared the efficacy of MCI to that of human judgments for detecting deception in scientists with expertise in biological materials. Sixty-four scientists were recruited for study; 12 met with a “terrorist” and were paid to make biological materials for illicit purposes. All 64 scientists were interviewed by investigators with law enforcement experience about the bio-threat issue. MCI elicited speech content differences in deceptive, compared to truthful scientists. This resulted in a classification accuracy of 84.4%; Accuracies for Human Judgments (interviewers/raters) were 54% and 46%, respectively. MCI required little time and its efficacy suggests it is reasonable to recommend its use to national security experts.