The Wall Street Journal reported this week that the Transportation Security Administration is testing sophisticated machines that use elaborate algorithms to determine whether air travelers have "hostile intent." The machines measure your sweat output, pulse rate and other tells while asking questions such as: "Are you planning to immigrate illegally?" "Are you smuggling drugs?" "Do these stupid questions make you feel like committing a terrorist act?"

OK, I made the last one up, and I shouldn't make fun because supposedly the Israelis have figured out how to make this stuff work. The thinking behind this program rests on the assumption that searching for every kind of potential weapon or explosive is too reactive. Find the bad motives, and the rest will follow.

If it works, great. But one of the frustrating reasons the U.S. government feels compelled to spend all of this time and energy coming up with computerized lie detectors is that civil libertarians can't trust airport security personnel to do the same thing. Why? Because it's possible for humans to be racist.

The TSA's more established security system, Screening Passengers by Observation Technique, or SPOT, relies on human intelligence instead of the artificial kind. Teams are trained to scrutinize passengers for more than 30 questionable behaviors, according to the Journal: "They look for obvious things like someone wearing a heavy coat on a hot day, but also for subtle signs like vocal timbre, gestures and tiny facial movements that indicate someone is trying to disguise an emotion."

This apparently is unacceptable for civil libertarians.

"Our concern is that giving TSA screeners this kind of responsibility and discretion can result in their making decisions not based on solid criteria but on impermissible characteristics such as race," the ACLU's Gregory T. Nojeim told the Journal.

In other words, while our enemies are coming up with ingenious ways to murder Americans, we're coming up with ingenious ways to search for our enemies in the nicest manner possible. No amount of training, it seems, can immunize against the real threat to America: the possibility that somewhere, at some time, a TSA cop might pull an Arab or South Asian out of a line at an airport unfairly and talk to them for five minutes.

Note: We're not talking about training security personnel to racially profile passengers. Quite the opposite. The ACLU's problem is with training officers not to racially profile if that training nonetheless gives them enough autonomy so that it's theoretically possible to take race into account. Continued...