[T]he system is generally designed to measure physical responses to hot-button questions like "Are you planning to immigrate illegally?" or "Are you smuggling drugs."If they really want to use this to find terrorists, they're going to have to test every single person that gets on a plane. According to the TSA, two million people fly everyday. That's 730 million people a year. Let's assume that 10 of them are terrorists. With a 4% false-positive rate and a 10% false-negative rate, that means 29 million innocent travelers are going to be detained as suspects, and one out of the 10 terrorists will still make it through security to conduct his or her dirty work. Is it worth it, or would the money be better spent preventing terrorism through intelligence work?Link
More than 80% of those approached are quickly dismissed, he says. The explanations for hiding emotions often are innocent: A traveler might be stressed out from work, worried about missing a flight or sad because a relative just died. If suspicions remain, the traveler is interviewed at greater length by a screener with more specialized training. SPOT teams have identified about 100 people who were trying to smuggle drugs, use fake IDs and commit other crimes, but not terrorist acts.
The company's goal is to prove it can catch at least 90% of potential saboteurs -- a 10% false-negative rate -- while inconveniencing just 4% of innocent travelers.
I took a upper division psychology class called Deception, the Brain, and Behavior not to long ago, which covered most of the techniques for mechanical lie detection, and related fields.
No device of the type described measures sweat levels. It instead measures Galvanic Skin Response (GSR) which are changes in the skin's electrical field tied to sweat production and stress. The idea is that the conductivity of your skin changes when you sweat, and you sweat when you are stressed or anxious. Of course, that also assumes you somehow unsweat when you are anxious, then tell the truth.
Second of all, such devices are fairly easy to beat when you know how. My class covered the fact that their are things you can do to degrade such devices accuracy to 50% or below (50% is chance). They might catch some illegal immigrants and untrained drug smugglers, but terrorists can use the many physical and mental countermeasures to such devices, and can even practice taking them. They may even utilize the devices in the airports themselves for training purposes, observing which techniques get them further questioning, and which allow them to pass.
This device will do nothing more then provide a false sense of security, while remaining permeable to terrorists and inconveniencing innocent travellers.>