THE WEEK IN WALKS.(using a person's gait as identification)

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, ...