Citing "the seismic shifts in digital technology" since the last time it considered the issue, the U.S. Supreme Court has ruled that people have a reasonable expectation that their cellphone's location data will be private. A reasonable expectation of privacy means that the Fourth Amendment's prohibition against unreasonable searches and seizures applies. Therefore, law enforcement must obtain a warrant before seeking cellphone location data except in emergency situations.
The case involved a man who was convicted of participating in a string of robberies. Law enforcement had bolstered its case by obtaining cellphone location data on the defendant. However, they obtained the records using a mere court order instead of a warrant. Warrants are to be issued only when police can show "probable cause" that a crime has been committed or is in progress. Court orders can be issued using a lower standard.
The lower courts and the Trump administration argued that a warrant wasn't necessary because cellphone location data constitutes a third-party business record. The ACLU, representing the defendant, argued that cellphone location data involves a much greater invasion of privacy than the telephone records of the past.
The majority of the court agreed. Chief Justice John Roberts reasoned that today's cellphones are so closely intertwined with modern life that tracking their location "achieves near perfect surveillance, as if [the government] had attached an ankle monitor to the phone's user."
Warrant exception for business records reined in
In the past, the courts have ruled that people have no expectation of privacy in business records kept by third parties, so the Fourth Amendment's warrant requirement does not apply to them.
This theory was largely based on a 1979 Supreme Court case involving a land-line phone and telephone records that consisted merely of a list of calls and their dates, times and length and the phone numbers involved. In that case, the court ruled that people had no right to expect the records to be kept private, so no warrant was required. In contrast, law enforcement would indeed need a warrant to record a phone call.
The new case recognizes that a great deal has changed since 1979. Today, cellphone location data can be effortlessly collected and used to track people's exact daily itinerary for years. People cannot opt out of this "near perfect surveillance" and still operate in the modern world, so the information needs to be kept private.
The ruling only applies to cellphone tracking information. The court made clear it was not ruling on other types of business records, including bank records.
The ACLU calls the case a "groundbreaking victory for Americans' privacy rights in the digital age."