(Adds reaction from ACLU, University of Texas expert)
WASHINGTON, June 5 (Reuters) - The U.S. Supreme Court on Monday agreed to hear a major case on privacy rights in the digital age that will determine whether police officers need warrants to access past cellphone location information kept by wireless carriers.
The justices agreed to hear an appeal brought by a man who was arrested in 2011 as part of an investigation into a string of armed robberies at Radio Shack and T-Mobile stores in the Detroit area over the preceding months. Police helped establish that the man, Timothy Carpenter, was near the scene of the crimes by securing cell site location information from his cellphone carrier.
At issue is whether failing to obtain a warrant violates a defendant's right to be free from unreasonable searches and seizures under the U.S. Constitution's Fourth Amendment.
The information that law enforcement agencies can obtain from wireless carriers shows which local cellphone towers users connect to at the time they make calls. Police can use historical data to determine if a suspect was in the vicinity of a crime scene or real-time data to track a suspect.
The legal fight has raised questions about how much companies protect the privacy rights of their customers. The big four wireless carriers, Verizon Communications Inc, AT&T Inc, T-Mobile US Inc and Sprint Corp, receive tens of thousands of requests a year from law enforcement for what is known as "cell site location information," or CSLI.
Carpenter's bid to suppress the evidence failed and he was convicted of six robbery counts. On appeal, the Cincinnati, Ohio-based 6th U.S. Circuit Court of Appeals upheld his convictions, finding that no warrant was required for the cellphone information.
Civil liberties lawyers say that police need "probable cause," and therefore a warrant, in order to avoid constitutionally unreasonable searches.
But, based on a provision of a federal law called the Stored Communications Act, the government said it does not need probable cause to obtain customer records. Instead, the government said, prosecutors must show only that there are "reasonable grounds" for the records and that they are "relevant and material" to an investigation.
Civil liberties groups assert that the 1986 law did not anticipate the way mobile devices now contain a wealth of data on each user. Carpenter is represented by the American Civil Liberties Union.
The Supreme Court has twice in recent years ruled on major cases concerning how criminal law applies to new technology, on each occasion ruling against law enforcement. In 2012, the court held that a warrant is required to place a GPS tracking device on a vehicle. Two years later, the court said police need a warrant to search a cellphone that is seized during an arrest.
Legal experts and civil liberties advocates said the case could become one of the most significant in years to address Fourth Amendment privacy issues raised in the digital age.
"Because cellphone location records can reveal countless private details of our lives, police should only be able to access them by getting a warrant based on probable cause," said Nathan Freed Wessler, a staff attorney with the ACLU Speech, Privacy and Technology Project.
"The time has come for the Supreme Court to make clear that the longstanding protections of the Fourth Amendment apply with undiminished force to these kinds of sensitive digital records," Wessler added.
Steve Vladeck, a national security and constitutional law professor at the University of Texas, said the case will have "enormous implications" over how much data the government can obtain from phone companies and other technology firms about their customers without a warrant.
"Courts and commentators have tried to figure out exactly when individuals will have a continuing expectation of privacy even in data they've voluntarily shared with a third party," Vladeck said. "This case squarely raises that question."
(Reporting by Lawrence Hurley; Additional reporting by Dustin Volz; Editing by Will Dunham)