The NYPD is working to develop a tool capable of detecting concealed firearms at a distance.
Police Commissioner Raymond Kelly says the department is working with the U.S. Department of Defense to develop the device that reads a form of natural energy akin to radiation.
If something is obstructing the flow of that energy, like a weapon, the device will highlight the object on a person's body.
The rendered image is often clear, said Kelly, though it can be affected by weather and other elements, and is more effective at night.
The idea would be to place a device in a vehicle and scan an area for weapons.
The New York Civil Liberties Union said it found the technology proposal "both intriguing and worrisome."
"On the one hand, if technology like this worked as it was billed, New York City should see its stop-and-frisk rate drop by a half-million people a year," said NYCLU executive director Donna Lieberman. "On the other hand, the ability to walk down the street free from a virtual police pat-down is a matter of privacy."
Lieberman called on NYPD to release more information about the technology, how it works and the dangers it presents.
"We've been looking at this for three years," said Kelly. "We've had our lawyers involved, and they don't see constitutional issues here."
Police say the technology is currently being tested but so far is only detecting weapons from about 13 feet away. They hope to increase the distance to about 80 feet.