Chief Justice John Roberts Jr. on Wednesday in New Zealand voiced concerns about the privacy implications of new technology that allows police to “see through walls,” echoing the alarm his newest colleague, Justice Neil Gorsuch, first raised nearly three years ago.

“There are devices now that can allow law enforcement to see through walls. Heat imaging and all this kind of thing,” Roberts reportedly said at the event in New Zealand. “Well, what does that do to a body of law that's developed from common law days in England about when you can search a house?”

In a December 2014 decision, then-Judge Gorsuch of the U.S. Court of Appeals for the Tenth Circuit led a three-judge panel in a Fourth Amendment case that confronted—but did not finally resolve—the privacy implications of a device that let the authorities essentially look inside private homes from the outside. In that case, the appeals court examined Doppler radar technology that is capable of detecting the presence of “human breathing and movement within” a house. The case was resolved on other grounds.

“It's obvious to us and everyone else in this case that the government's warrantless use of such a powerful tool to search inside homes poses grave Fourth Amendment questions. New technologies bring with them not only new opportunities for law enforcement to catch criminals but also new risks for abuse and new ways to invade constitutional rights,” Gorsuch wrote. “We have little doubt that the radar device deployed here will soon generate many questions for this court and others along both of these axes.”

The Supreme Court in May 2015 denied the petition for review. The U.S. Department of Justice had waived any response to the petition.

The justices have not yet confronted police-controlled radar devices—“packed into a hand-held unit 'about 10 inches by 4 inches wide, 10 inches long,'” as Gorsuch described in the case Denson v. United States. But as The Associated Press reported Wednesday, Roberts warned in his conversation with the dean of Victoria University of Wellington that constitutional questions about new technology are coming quickly to the high court.

Heat-imaging technology was at the heart of the 2001 case Kyllo v. United States. The justices, in a ruling from Justice Antonin Scalia, said the warrantless use of a thermal imaging device—to show evidence of marijuana plants growing inside a house—violated the Fourth Amendment.

The chief justice on Wednesday also noted his court's 2014 decision in Riley v. United States, which held that the warrantless search and seizure of the digital contents of a cellphone during an arrest violated the Fourth Amendment. Roberts wrote that decision.

“I'll say it here: Would you rather have law enforcement rummaging through your desk drawer at home, or rummaging through your iPhone?” Roberts said Wednesday. “I mean, there's much more private information on the iPhone than in most desk drawers.” (The National Constitution Center's daily blog has more on Roberts' remarks here.)

The justices also have confronted Fourth Amendment issues recently involving police use of GPS tracking devices. In the 2012 decision United States v. Jones, a unanimous court held that prosecutors violated the Fourth Amendment when they attached a GPS device to suspected drug kingpin Antoine Jones's Jeep and monitored his movements for 28 days.

In October, the high court will consider another technology-related challenge. The justices agreed to hear arguments on whether police need a search warrant to access cellphone location data to track the movements of a suspect. In that case, Carpenter v. United States, police used the cellphone tower records to track Timothy Carpenter's movements over 127 days to establish he was at a string of robberies in two states in 2010 and 2011.

Chief Justice John Roberts Jr. on Wednesday in New Zealand voiced concerns about the privacy implications of new technology that allows police to “see through walls,” echoing the alarm his newest colleague, Justice Neil Gorsuch, first raised nearly three years ago.

“There are devices now that can allow law enforcement to see through walls. Heat imaging and all this kind of thing,” Roberts reportedly said at the event in New Zealand. “Well, what does that do to a body of law that's developed from common law days in England about when you can search a house?”

In a December 2014 decision, then-Judge Gorsuch of the U.S. Court of Appeals for the Tenth Circuit led a three-judge panel in a Fourth Amendment case that confronted—but did not finally resolve—the privacy implications of a device that let the authorities essentially look inside private homes from the outside. In that case, the appeals court examined Doppler radar technology that is capable of detecting the presence of “human breathing and movement within” a house. The case was resolved on other grounds.

“It's obvious to us and everyone else in this case that the government's warrantless use of such a powerful tool to search inside homes poses grave Fourth Amendment questions. New technologies bring with them not only new opportunities for law enforcement to catch criminals but also new risks for abuse and new ways to invade constitutional rights,” Gorsuch wrote. “We have little doubt that the radar device deployed here will soon generate many questions for this court and others along both of these axes.”

The Supreme Court in May 2015 denied the petition for review. The U.S. Department of Justice had waived any response to the petition.

The justices have not yet confronted police-controlled radar devices—“packed into a hand-held unit 'about 10 inches by 4 inches wide, 10 inches long,'” as Gorsuch described in the case Denson v. United States. But as The Associated Press reported Wednesday, Roberts warned in his conversation with the dean of Victoria University of Wellington that constitutional questions about new technology are coming quickly to the high court.

Heat-imaging technology was at the heart of the 2001 case Kyllo v. United States. The justices, in a ruling from Justice Antonin Scalia, said the warrantless use of a thermal imaging device—to show evidence of marijuana plants growing inside a house—violated the Fourth Amendment.

The chief justice on Wednesday also noted his court's 2014 decision in Riley v. United States, which held that the warrantless search and seizure of the digital contents of a cellphone during an arrest violated the Fourth Amendment. Roberts wrote that decision.

“I'll say it here: Would you rather have law enforcement rummaging through your desk drawer at home, or rummaging through your iPhone?” Roberts said Wednesday. “I mean, there's much more private information on the iPhone than in most desk drawers.” (The National Constitution Center's daily blog has more on Roberts' remarks here.)

The justices also have confronted Fourth Amendment issues recently involving police use of GPS tracking devices. In the 2012 decision United States v. Jones, a unanimous court held that prosecutors violated the Fourth Amendment when they attached a GPS device to suspected drug kingpin Antoine Jones's Jeep and monitored his movements for 28 days.