These police radars let officers 'see' inside homes

At least 50 law enforcement agencies across the country have access to radar devices that will allow them to sense human movement within homes. The devices were first designed as battlefield technology for use in Iraq and Afghanistan.

The radars, which were deployed for FBI and police units more than two years ago, allow officers to see through walls to determine whether people are inside buildings. The practice was unknown to the public until a federal appeals court in Denver revealed last month that officers had used the Range-R device before entering a house to arrest a man who violated his parole.

In the Denver case, the judge said that "the government's warrantless use of such a powerful tool to search inside homes poses grave Fourth Amendment questions." USA Today adds that the radars were deployed "with little notice to the courts and no public disclosure of when or how they would be used," and they raise privacy concerns, since the Supreme Court "has said officers generally cannot use high-tech sensors to tell them about the inside of a person's house without first obtaining a search warrant."