They may be great at keeping you from taking your bottle of water onto the plane, but when it comes to catching actual bombs and guns they're not very good:
Screeners at Newark Liberty International Airport, one of the starting points for the Sept. 11 hijackers, failed 20 of 22 security tests conducted by undercover U.S. agents last week, missing concealed bombs and guns at checkpoints throughout the major air hub's three terminals, according to federal security officials.
One of the security officials familiar with last week's tests said Newark screeners missed fake explosive devices hidden under bottles of water in carry-on luggage, taped beneath an agent's clothing and concealed under a leg bandage another tester wore.
The official said screeners also failed to use handheld metal-detector wands when required, missed an explosive device during a pat-down and failed to properly hand-check suspicious carry-on bags. Supervisors also were cited for failing to properly monitor checkpoint screeners, the official said. "We just totally missed everything," the official said.
As I've written before, this is actually a very hard problem to solve:
Airport screeners have a difficult job, primarily because the human brain isn't naturally adapted to the task. We're wired for visual pattern matching, and are great at picking out something we know to look for -- for example, a lion in a sea of tall grass.
But we're much less adept at detecting random exceptions in uniform data. Faced with an endless stream of identical objects, the brain quickly concludes that everything is identical and there's no point in paying attention. By the time the exception comes around, the brain simply doesn't notice it. This psychological phenomenon isn't just a problem in airport screening: It's been identified in inspections of all kinds, and is why casinos move their dealers around so often. The tasks are simply mind-numbing.
To make matters worse, the smuggler can try to exploit the system. He can position the weapons in his baggage just so. He can try to disguise them by adding other metal items to distract the screeners. He can disassemble bomb parts so they look nothing like bombs. Against a bored screener, he has the upper hand.
But perversely, even a mediocre success rate here is probably good enough:
Remember the point of passenger screening. We're not trying to catch the clever, organized, well-funded terrorists. We're trying to catch the amateurs and the incompetent. We're trying to catch the unstable. We're trying to catch the copycats. These are all legitimate threats, and we're smart to defend against them. Against the professionals, we're just trying to add enough uncertainty into the system that they'll choose other targets instead.
What that means is that a basic cursory screening is good enough. If I were investing in security, I would fund significant research into computer-assisted screening equipment for both checked and carry-on bags, but wouldn't spend a lot of money on invasive screening procedures and secondary screening. I would much rather have well-trained security personnel wandering around the airport, both in and out of uniform, looking for suspicious actions.
Remember this truism: We can't keep weapons out of prisons. We can't possibly keep them out of airports.