The New York Police Department is currently testing a new remote gun detection system that could potentially raise some concerns around both privacy and health risks. The system is based on terahertz waves, which sit between microwaves and the infrared in the electromagnetic spectrum. These waves can pass through non-conducting material, like clothing, but they would be blocked by objects like guns. The device the NYPD is testing would be able to capture terahertz waves emitted by people or objects — if a suspicious concealed object blocked the waves, police would be able to identify it as a firearm and take appropriate action. Currently, the system is only effective between three and five meters, but the NYPD is hoping to have it work at distances up to 25 meters. Terahertz waves are a natural part of the environment and aren't believed to be harmful because the radiation level is so low — but if tools like this dramatically increase the level of terahertz waves people are exposed to, further testing may be needed to ensure there aren't any ill effects.

Not surprisingly, there are also privacy concerns surrounding this technology. The New York Civil Liberties Union said that there's no information about how accurate this new technology is and that the public will need more information on it to properly judge its safety and whether it presents any dangers. There's also the concern that citizens should be able to walk the streets "free from a virtual pat-down." On the other hand, if these devices are effective, they could stop the NYPD's "stop-and-frisk" campaign — a controversial and largely random search of more than 500,000 New Yorkers every year. A lot of privacy concerns may have to do with the lack of clarity around how this tool will be deployed: for right now, the NYPD only imagines using it in "reasonably suspicious circumstances," but that certainly is a phrase open to interpretation. There's no word on when exactly this system might roll out, but we imagine there will be a lot more testing and hopefully more clarification on where and when it can be used.