At least 16 people later linked to terror plots passed through U.S. airports undetected by federal officials who were on duty to spot suspicious behavior, according to a government report. The airport-based officials were part of a federal behavior detection program designed to spot potential terrorists and others who pose a threat to aviation. The program, started in 2003, is one of 20 layers built into the nation’s aviation security system. The Government Accountability Office (GAO) questioned the scientific basis of the entire program in a report released May 20. The program is dubbed SPOT — Screening Passengers by Observation Techniques. It was instituted by the Transportation Security Administration “without first validating the scientific basis for identifying passengers in an airport environment,” the GAO said. “A scientific consensus does not exist on whether behavior-detection principles can be reliably used for counterterrorism purposes,” the congressional auditors said. The agency did not agree with all of the GAO’s findings. “TSA strongly believes that behavior detection is a vital layer in its aviation security strategy. ... Leaders within the community of behavior detection researchers agree,” the director of the Homeland Security Department’s GAO liaison office said in a response included in the report.

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