How do you pick out a terrorist from the millions of people who board planes each year? You can search through their bags, pat them down, go over their passports and check their IDs, but terrorists, one must assume, are crafty types. Assuming whatever contraband they require has made its way to the plane, all you really have left to ID the perp is what he's got inside his head.

In lieu of brainwave scanners being installed at LAX, the U.S. Army is looking to alternative ways to determine who's got crime on their mind. To wit, the military is looking for proposals for large-scale biometric sensors that would scan travelers and examine their "expressions, gait, and pose" and look for "abnormal perspiration and changes in body temperature" in order to track down evildoers.

It's a lot like a sit-down lie detector, only with the scanning done by a silent "eye in the sky." The idea is essentially that people with something to hide get subconsciously nervous, and that nervousness becomes manifest in excess body heat, sweating, and other erratic behavior. Of course, standard polygraph tests are notoriously "beatable" by prepared test-takers, and it's unclear whether a distant scanning system (even one with extreme zoom capabilities) would be more or less accurate. (While the subject would theoretically be less aware of the scanning going on, the limitations of the scanning would likely make it less thorough than a formal polygraph.)

Naturally, such ideas lead one to wonder about the false positives that might arise due to, say, people arriving late to the airport and running (sweatily) to catch their planes, or the natural confusion and frustration present on many travelers' faces when they find themselves in an airport that's foreign to them or when they have to deal with a couple of screaming kids and long lines at the security checkpoint. Put another way: If you arrive at the airport already upset and angry, you'd be that much more likely to be selected for secondary screening, which will only make you even more upset and angry.

Right now this scanning system is only a research project, and we're likely years away before any serious discussion of actually putting cameras like this into airports begins, and that's if they even prove effective at all. Still, privacy advocates are likely to have a field day shredding this notion, an ominous precursor to Big Brother-like "thoughtcrime" accusations that would make anyone a little uneasy.