“Since 9/11 preventing terrorism is a priority,” Rosenfeld said. “Sometimes you catch suspicious people entering a building. You suspect that they’re terrorists, and you have some leads from the chatter. You’ve heard they’re going to attack one city or another in one fashion or another on one date or another. Our hope is that our new complex protocol – different from the first P300 technology developed in the 1980s – will one day confirm such chatter in the real world.”
I’m sure that there’s always some secret that only the terrorists and the surveillance geeks know, that could be used as an effective probe for this technique. Because otherwise you’re going to test positive for every malcontent who’s thought about carrying out a terrorist attack in some particular way on a particular date in a particular place, every security officer or first responder who’s worried about defending against some particular terrorist attack, every news junkie who’s considered that a particular place on a particular date might be a terrorist target… And there are roughly a million times as many of those people as actual terrorists, so unless you’re 99.9999% accurate, you’re diverting resources from something that might actually help.
Schneier has made this point over and over again: tagging the people who are evildoers, on a day to day basis, is not nearly as important as not mistakenly tagging the people who aren’t.