U.S. Supreme Court justices from across the spectrum voiced concern on Wednesday about personal privacy and government snooping in a case that tests whether police can obtain cellphone location data of suspects without a warrant.

In Carpenter v. United States, the case before the court, the Justice Department asserts that acquiring cellphone data from a third party carrier does not constitute a search under the Fourth Amendment, and therefore does not require a warrant.

But the ACLU, which represents defendant Timothy Carpenter, counters that he had an expectation of privacy in that data, especially when the location records tracked 127 days of Carpenter's movements.

Justices seemed to lean in favor of the defendant, with some displaying a libertarian streak and others sounding the alarm about personal privacy.

“A cellphone can be pinged in your bedroom,” said Justice Sonia Sotomayor at one point. “It can be pinged at your doctor's office. It can ping you in the most intimate details of your life. Presumably at some point even in a dressing room as you're undressing.”

Addressing ACLU lawyer Nathan Wessler, who represented Carpenter, Justice Samuel Alito Jr. said, “I agree with you, that this new technology is raising very serious privacy concerns, but I need to know how much of existing precedent you want us to overrule or declare obsolete.”

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♦ READ MORE: Q&A: ACLU's Wessler on the SCOTUS Cell-Site Data Case 

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Justice Anthony Kennedy mused that most consumers probably know that companies keep cellphone data about customers. But he added, “I don't think there's an expectation that people are following you for 127 days.”

Justice Neil Gorsuch offered another criticism of the government argument, suggesting that Carpenter may have had a property right in the cellphone location data compiled for the police.

The libertarian Cato Institute and other groups including the Competitive Enterprise Institute filed a brief on Carpenter's side urging a property rights approach that might simplify the Fourth Amendment analysis.

Deputy Solicitor General Michael Dreeben balked at the idea, telling Gorsuch, “I suppose that if you are insisting that I acknowledge that it's a property right, some consequences are going to follow … I don't think you can make that assumption.”

But Gorsuch, seemingly irritated, pushed on: “Let's stick with my hypothetical, counsel, OK? I know you don't like it. I get that.”

Chief Justice John Roberts Jr. took the unusual step of telling the lawyers just before the argument that they had an extra 10 minutes each to make their case.

“I don't think you'll have trouble filling it,” Roberts said, and he was correct. Questions about more limited searches, third-party status and whether or not consumers know their locations are being tracked flew back and forth. But justices seemed uncertain how to draw the line defining legitimate searches of data held by phone companies at a time when cellphones are so common.

As Justice Stephen Breyer put it, “This is an open box. We know not where we go.”

U.S. Supreme Court justices from across the spectrum voiced concern on Wednesday about personal privacy and government snooping in a case that tests whether police can obtain cellphone location data of suspects without a warrant.

In Carpenter v. United States, the case before the court, the Justice Department asserts that acquiring cellphone data from a third party carrier does not constitute a search under the Fourth Amendment, and therefore does not require a warrant.

But the ACLU, which represents defendant Timothy Carpenter, counters that he had an expectation of privacy in that data, especially when the location records tracked 127 days of Carpenter's movements.

Justices seemed to lean in favor of the defendant, with some displaying a libertarian streak and others sounding the alarm about personal privacy.

“A cellphone can be pinged in your bedroom,” said Justice Sonia Sotomayor at one point. “It can be pinged at your doctor's office. It can ping you in the most intimate details of your life. Presumably at some point even in a dressing room as you're undressing.”

Addressing ACLU lawyer Nathan Wessler, who represented Carpenter, Justice Samuel Alito Jr. said, “I agree with you, that this new technology is raising very serious privacy concerns, but I need to know how much of existing precedent you want us to overrule or declare obsolete.”

---

♦ READ MORE: Q&A: ACLU's Wessler on the SCOTUS Cell-Site Data Case 

---

Justice Anthony Kennedy mused that most consumers probably know that companies keep cellphone data about customers. But he added, “I don't think there's an expectation that people are following you for 127 days.”

Justice Neil Gorsuch offered another criticism of the government argument, suggesting that Carpenter may have had a property right in the cellphone location data compiled for the police.

The libertarian Cato Institute and other groups including the Competitive Enterprise Institute filed a brief on Carpenter's side urging a property rights approach that might simplify the Fourth Amendment analysis.

Deputy Solicitor General Michael Dreeben balked at the idea, telling Gorsuch, “I suppose that if you are insisting that I acknowledge that it's a property right, some consequences are going to follow … I don't think you can make that assumption.”

But Gorsuch, seemingly irritated, pushed on: “Let's stick with my hypothetical, counsel, OK? I know you don't like it. I get that.”

Chief Justice John Roberts Jr. took the unusual step of telling the lawyers just before the argument that they had an extra 10 minutes each to make their case.

“I don't think you'll have trouble filling it,” Roberts said, and he was correct. Questions about more limited searches, third-party status and whether or not consumers know their locations are being tracked flew back and forth. But justices seemed uncertain how to draw the line defining legitimate searches of data held by phone companies at a time when cellphones are so common.

As Justice Stephen Breyer put it, “This is an open box. We know not where we go.”