科学美国人60秒:Radar Makes All Houses Glass

Doppler radar has been a weather forecaster’s best friend for decades. But more recently law enforcement has found another application. For the past two years the FBI, U.S. Marshals and other agencies have used a handheld Doppler radar machine to conduct surveillance through solid walls. That’s according to USA Today.
 
Called the Range-R, this Doppler device sends radio frequency signals through concrete, wood and other nonmetal building materials and can measure the distance between itself and any moving objects on the other side. The Range-R can detect even subtle motion like breathing, although it can’t yet identify whether the respiration is coming from a person or their pet. Some 200 of the $6,000 devices have been sold.
 
The problem is that law enforcement has used the Range-R sort of “under the radar,” if you will, sometimes employing it without a search warrant. The issue was brought to light in a court case after the device helped U.S. Marshals catch a parole violator at a house in Wichita. Federal appeals court judges were not pleased. 
 
So that’s the current situation: police use of the technology to gain an edge versus concerns about violations of Fourth Amendment protections against unreasonable searches. Stay tuned for the developing legal decisions regarding this particular Doppler effect.
 
—Larry Greenemeier