The NYPD and DOD are developing a way to scan people for guns from a safe distance. Can the new system survive the many privacy concerns it's bound to bring up?

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New York City Mayor Michael Bloomberg has been notoriously tough on guns, which is understandable when you consider 61% of the city’s homicides in 2010 were gun-related. But frisking people on the street from more than 80 feet away? That’s bound to raise a few eyebrows, even among those in the pro-gun-control camp.

The new technology utilizes terahertz waves, which sit on the electromagnetic spectrum between microwaves and infrared. They’ve been used to do everything from detect cancer to create 3D images of teeth for dentists.

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The reason that the NYPD is so interested terahertz waves is that they pass through nonconductive materials like clothes, but can’t penetrate metal — like, say, the steel in a semi-automatic pistol. That means if you scan someone, you can look for spots where a person’s natural terahertz radiation is blocked, most likely by a metal object.

The benefits for police officers are obvious. They can essentially sit back in a specially-equipped van and scan anyone they suspect of carrying a gun from a safe distance. Right now it only works from three or four feet away, but department spokesman Paul J. Browne told the New York Times that the NYPD — in coordination with the Department of Defense — hopes to increase its range to 25 meters, or 82 feet.

This, obviously, has created some privacy concerns, as the idea of police officers scanning anyone on the street at their discretion is more than a little scary to some people. Right now the New York Civil Liberties Union is taking a cautious stance on the subject, stating the following through its executive director Donna Lieberman:

Like all New Yorkers, we are eager for solutions to the intractable problem of gun violence. We find this proposal both intriguing and worrisome. On the one hand, if technology like this worked as it was billed, New York City should see it’s stop-and-frisk rate drop by a half-million people a year. On the other hand, the ability to walk down the street free from a virtual police pat-down is a matter of privacy. We have no idea how this technology works, if it is effective, and what it’s error rate is. If the NYPD is moving forward with this, the public needs more information about this technology, how it works and the dangers it presents.

The NYCLU, working with the NYPD’s numbers, figures that around 88% of stop-and-frisk situations (where police see a person on the street, stop them and then frisk them) result in nothing being found. Ostensibly, this technology would allow the police to avoid physical risk while sparing pedestrians the unnecessary indignity of being frisked on the street.

The flipside of the coin is that we don’t know what the restrictions on this technology will be. Will police feel free to increase the number of people they “frisk” now that the subjects of their virtual pat-downs won’t even know about it? How accurate is this technology? Will people carrying around iPods and other innocuous metal objects all of a sudden become suspicious characters in the eyes of the police?

It’s a bit early to make a judgment now; the technology is still being tested at the NYPD’s Rodman’s Neck shooting range in the Bronx. But you can bet that civil liberties groups and other police departments from across the country will be watching its progress closely.

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