THE WEEK IN WALKS , by Ben McGrath, The New Yorker, May 26, 2003  

The recent revelation that the Defense Department may soon be using radar surveillance to monitor the way we walk, in an attempt to identify terrorists through their “gait signatures,” was alarming not only to diehard civil libertarians but also to skulkers, stumblers, and zigzaggers everywhere. Researchers at Georgia Tech, sponsored by the Defense Advanced Research Projects Agency, have reported a success rate of between eighty and ninety-five per cent in identifying individuals simply by their gaits, and they hope before long to increase the accuracy to “the high ninety percent range,” as one researcher, Jon Geisheimer, noted in a press release. “We need technology to find the bad guys at a distance,” he said.

This news happened to accompany vague F.B.I. warnings of a possible “devastating attack” on New York, Boston, Washington, and, perplexingly, the nation’s beaches (by jellyfish? tidal waves? fat hairy men with kadima paddles?). New York, at least, was once again on edge. Military units descended on the city, along with an intermittent rain. Urged by President Bush to “be alert,” people couldn’t be faulted for succumbing to the impulse to scrutinize the gaits of their fellow-citizens, though, in the absence of radar technology, their findings were preliminary, at best.

On Tuesday, passengers aboard an Amtrak train from Washington to Boston grew suspicious of a man lurching in the aisles with a peculiar plastic jug. Train service was suspended for a couple of hours—and part of Penn Station was shut down—until the authorities determined that the man in question, a Liberian immigrant, was just carrying cooking oil. At Penn Station the next day, Army National Guardsmen, in combat boots and full camouflage, with M16s slung over their right shoulders, patrolled the corridors. Their gait was distinctive—an almost bowlegged, gunslinger’s waddle, a result, presumably, of the stuffed pouches and pockets that hung like saddlebags from their pants.

At around 2 p.m., a green suitcase attracted attention, mainly for being unattached to anyone with a gait to be wary of. Officers from the N.Y.P.D. Emergency Service Unit, wearing helmets and carrying machine guns, converged on it, accompanied by a bomb-sniffing dog. Another false alarm. The cops retreated stiffly (tight chin straps) to their post near the train-information board and looked on as a call went out for the 2:29 to Oyster Bay, setting off a small commuter stampede. The officers’ eyes began dancing from side to side in rapid gait-scan mode. No terrorists in this batch.

Upstairs, in the Theatre at Madison Square Garden, the commencement ceremony for the New School was about to begin. On Seventh Avenue, ushers in purple gowns sorted approaching pedestrians into two categories: graduating students (“This way, please. Report to the Expo Center for marching instructions”) and guests (“Keep walking toward the box office”). The former were recognizable both for their hurried pace and, in roughly half the cases, for a tottering that suggested an unfamiliarity with high heels. This called into question the assertion by one of the researchers at Georgia Tech that “a woman switching from flats to high heels probably wouldn’t change her signature significantly.” (As Jeffrey Boyd, the co-author of the seminal walking paper “Recognizing People by Their Gait,” said last week, “It’s pretty clear that changing footwear does change gaits. Put a pebble in one shoe, you’re going to walk a little funny.”) At any rate, there seemed to be little to fear here.

Several hours passed without incident. After midnight, along the sidewalks west of Times Square, Navy personnel could be identified, with about eighty-to-ninety-five-per-cent accuracy, by their inability to walk in a straight line. These military men, ashore for Fleet Week, were not on active security duty (“We’re here to party,” Kenny, from the U.S.S. Yorktown, announced), and they still seemed to be listing, tacking, and even coming about, but they, too, were keeping a vigilant eye on the movements of those around them. Outside Smith’s Bar and Restaurant, on Forty-fourth Street, each passing female drew stares from the crew of the U.S.S. Philippine Sea, and if her gait, viewed from behind, passed muster, one of the sailors would call out, “Where have you been all my life?”