Patting travelers down at the airport and making them walk through a metal detector with their shoes off may not be enough to prevent terrorist attacks. So Homeland Security has spent some $40 million on two projects to figure out whether it can use nonverbal cues to screen for malicious intent. "We're trying to detect a crime before it has occurred," said Bob Burns, No. 2 at the Homeland Security Advanced Research Project Agency. Though many in the scientific community have been quick to dismiss the work, Homeland Security researchers believe they might be able to use devices like video game boards and biometric sensors or analyze minute facial twitches to detect hostile plans. Whether it will ever yield any results is unclear—and even the Transportation Security Administration knows that. “A scientific consensus does not exist on whether behavior detection principles can be reliably used for counter-terrorism purposes,” it said in a report to Congress.