The new, expensive backscatter x-ray scanners installed at airports have already been shown to be fairly worthless because they can’t stop a determined individual from smuggling contraband onto an airplane in a body cavity. But that’s not all; it appears the scanners can easily be defeated by a kitchen rolling pin and a roll of tape.
It is very likely that a large (15–20 cm in diameter), irregularly-shaped, cm-thick pancake with beveled edges, taped to the abdomen, would be invisible to this technology, ironically, because of its large volume, since it is easily confused with normal anatomy. Thus, a third of a kilo of PETN, easily picked up in a competent pat down, would be missed by backscatter “high technology”. Forty grams of PETN, a purportedly dangerous amount, would fit in a 1.25 mm-thick pancake of the dimensions simulated here and be virtually invisible. Packed in a compact mode, say, a 1 cm×4 cm×5 cm brick, it would be detected.
It appears the only thing needed to defeat the new porno scanners is to mold the plastic explosives into a thin irregular shape next to the body so the scanner reads the mass as additional stomach fat. While not specifically addressed in the paper, one might assume other thin objects could also be easily hidden under an irregular pancake masked as part of the human body.
In other words, the porno-scanners appear to “work” only if we assume potential terrorists will be nice enough to hide explosives as easily recognized bricks. That is why it is called “security theater.”