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More than a dozen prominent tech companies are urging the US Supreme Court to make it harder for law enforcement officials to obtain individuals' sensitive cell phone data.

The companies filed a friend-of-the-court brief with the Supreme Court on Monday, arguing that law enforcement officials should be required to obtain a warrant before accessing data on a phone customer's location.The 44-page brief, signed by Apple, Facebook, Google and Verizon, among several others, said greater privacy protections are needed as companies increasingly collect user data by way of digital technologies.

"That users rely on technology companies to process their data for limited purposes does not mean that they expect their intimate data to be monitored by the government without a warrant," said the brief (PDF).

Phone location data has become increasingly important to investigations in recent years, as it can pinpoint a suspect's location by triangulating the signal among cell towers. Cell phone companies regularly get requests from police and other government agencies tied to investigations.

The issue is central to the appeal filed by Timothy Carpenter, who was convicted in 2011 of a series of armed robberies in Ohio and Michigan with the help of past cell phone location data. Officers dug through 127 days' worth of data provided by MetroPCS and Sprint. From that, they pulled together about 12,898 different locations for Carpenter during the time of the robberies.

Carpenter's conviction hinged on his phone location data, and he lost an appeal at the Sixth Circuit Court of Appeals last April. In the appellate decision, the judges ruled that phone location data didn't merit Fourth Amendment protections against unreasonable searches and that the officers didn't need a warrant, as Carpenter's lawyers argued.

The Supreme Court's review of the case comes amid growing scrutiny of law enforcement surveillance practices. The court's decision will set an important precedent on how law enforcement can use technology to gather evidence in cases.

"Tech firms are sending a very clear message that the law needs to catch up with the technology that is now an integral part of our everyday lives," Nathan Freed Wessler, an attorney with the American Civil Liberties Union who is representing Carpenter, said in a statement.

The US Justice Department, which is defending law enforcement procedures in the case, declined to comment.

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