You can thank Umar Farouk Abdulmutallab and his fizzled underwear bomb for the big rollout of full-body airport scanners that began in 2010, shortly after the Nigerian terrorist tried to bring down a flight from Amsterdam to Detroit on Christmas Day in 2009. But it might make more sense to blame the Transportation Security Administration (TSA), since it seems quite unlikely that the machines would have detected the explosive powder sewn into his briefs. In a March 2010 report, the Government Accountability Office (GAO) said "it remains unclear whether the AIT [advanced imaging technology] would have been able to detect the weapon Mr. Abdulmutallab used in his attempted attack." Things became clearer this month following another aborted underwear bombing, this one involving a double agent working for Saudi intelligence. After all, why would Al Qaeda try the same technique again, now that we have all those expensive machines peering through passengers' clothing, looking for just this sort of device?

"Quite frankly," an unnamed but "high-ranking" Department of Homeland Security official told The New York Times last week, "I think the likelihood is high that he or she or whatever the device was would have been picked up through the screening abroad at the last point of departure, based on what we have in place in those locations and the partnerships we have." Notably, this official did not say the explosives would have shown up on a full-body scanner. Rep. Darrell Issa (R-Calif.), chairman of the House Oversight and Government Reform Committee, pressed this point at a May 9 congressional hearing:

"Just yesterday," Mr. Issa began, "Janet Napolitano — Secretary Napolitano — said there is a high likelihood that Advanced Imaging Technology would have detected the new sophisticated underwear bomb used in the recent or attempted to be used in the recent plot in Yemen. Do you agree that there is a high likelihood that advanced imaging would have caught the new bomb?" he asked [a GAO] auditor who had worked on an examination of the T.S.A.

"That's a very interesting question," said Stephen Lord, the director of homeland security and justice issues for the Government Accountability Office. "I would have great difficulty answering that in open sessions, sir. We've done a classified report."

Mr. Issa said: “We'll take that, and I'm going to predict that it's going to be no, they couldn't. But the actual answer will remain classified."

Well, not really. Issa presumably has seen the full report, so he knows the answer is no. Likewise Rep. John Mica (R-Fla.), chairman of the House Transportation and Infrastructure Committee, who recently told The New York Times, "The latest device, which was designed specifically to thwart what we’ve got in place, probably would've gotten through rather easily." TSA Administrator John Pistole conceded that "no one knows without equivocation whether that kind of device would get through until we test it." A report issued last week by Issa's committee and Mica's committee calls the AIT scanners "ineffective." Pistole says "we're working with the manufacturers to improve the technology." He emphasizes that the scanners are just "one of the layers of defense against potential bombs." Ah, the layers! Even if none of them works on its own, together they achieve a security synergy that stops underwear bombers. Notice how former TSA Administrator Kip Hawley dances around the effectiveness of full-body scanners in his comments to the Times:

The screening is vastly improved since 2009. The question is whether the person would have gotten the bomb on, and would the bomb have worked. On both of those I would say no.

No, the question is whether these expensive, privacy-invading machines can detect a form-fitting underwear bomb, which was the justification for installing so many of them and for using them as a primary screening tool. Hawley's evasiveness is reminiscent of the TSA's response to the dude who posted a video in March explaining "How to Get Anything Through TSA Nude Body Scanners."  As Mike Riggs noted, a TSA blogger replied that "for obvious security reasons, we can't discuss our technology's detection capability in detail," while assuring the flying public that "imaging technology has been extremely effective in the field" but cautioning that AIT scanners are just "one layer of our 20 layers of security." Two of the other layers he mentioned: "behavior detection," which Mica points out has never been validated, and "federal air marshals," which Ohio State University political scientist John Mueller and University of Newcastle engineering professor Mark Newcastle deem "not worth the money" in their 2011 book on anti-terrorism measures.

In a 2010 column, I noted the short-lived passenger rebellion against full-body scanners. For additional examples of fighting terrorism with invasive incompetence, see J.D. Tuccille's recent piece telling "The Terrible Truth About the TSA" and James Bovard's classic 2004 exposé "Dominate. Intimidate. Control." More on the TSA here.