WASHINGTON -- The Supreme Court weighed privacy rights in the digital era Wednesday, confronting the question of whether the police can obtain a suspect's cellphone records to track his travels for four months without a search warrant.
The answer appeared to be: "No."
During an intense oral argument, the nine justices sounded divided along unusual lines, but most appeared to agree that collecting cell tower data to track a suspect's movements for 127 days amounted to an unreasonable search.
But it was unclear whether they would decide simply to limit how long the police may track a suspect through his mobile phone, or instead rule broadly that cellphone records are private and off limits to the police or the FBI without a search warrant.
That would amount to a major change in the law, the government told the court, and one that could hamper investigations when police do not know who committed a murder, robbed a bank, abducted a child or set off a bomb.
In those cases, investigators often obtain data from cellphone towers to narrow the list of people who were nearby when the crime was committed. They would not have "probable cause" to obtain a warrant for a particular suspect and his cellphone.
By contrast, the case heard Wednesday began when police learned that Timothy Carpenter was the leader of a robbery ring in Detroit. Several of his cohorts had confessed.
To build their case, prosecutors obtained a magistrate's order requiring several wireless carriers to turn over records of 16 phone numbers that Carpenter had used over four months. The data confirmed he was nearby when his accomplices carried out eight robberies of Radio Shack stores. He was convicted and sentenced to 116 years in prison.
Under current federal law, the prosecutor had to show the magistrate only that the cellphone records were "relevant and material to an ongoing criminal investigation."
In his appeal, ACLU lawyer Nathan Wessler urged the court to set a higher standard and to require prosecutors to show "probable cause" that the suspect was engaged in crime.