The capacity of cellphones to track people's movements and provide a vivid picture of their private lives poses a substantial and growing threat to privacy.
That is why a federal appeals court ruling Wednesday restricting the government's access to location data stored by cellphone companies is so important. In a case involving a man convicted of several robberies in South Florida, the 11th U.S. Circuit Court of Appeals said law enforcement agencies could get location records from cellphone companies only if they first obtained a probable cause warrant from a judge.
The U.S. attorney's office in Miami had built a case against Quartavious Davis partly on the basis of records obtained from his cellphone company showing where he had used his phone over 67 days. The records placed him at the site of the robberies. Prosecutors got access to the data after obtaining an order from a federal magistrate judge by demonstrating that the information was "relevant and material" to their investigation, which is easier to demonstrate than probable cause.