The NYPD is testing a new device that could allow police to detect concealed weapons without a body search. Commissioner Ray Kelly announced the use of the terahertz-wave detection device during a speech before the New York City Foundation Wednesday.

Terahertz is described as a natural form of energy emitted by people and objects. Kelly said if something is blocking the flow of radiation – like a gun hidden in someone’s clothes – the device will highlight that object.

Donna Lieberman, the executive director of the New York Civil Liberties Union, said the device could be a promising alternative to the NYPD’s stop and frisk policy – but that the technology could also raise other constitutional concerns.

"We have to be mindful of the concerns that everybody has about their privacy, even when they’re out on the street, because it’s our bodies,” she said.

She also said the NYCLU has a lot of questions about the new technology.

“I hope the police department will provide us with a transparent process so that we, so that the public understands, you know, exactly what this technology entails and what promises it offers,” she said.

Commissioner Kelly said the NYPD has been working with the vendor and the London Metropolitan Police to develop the device.