https://www.theregister.co.uk/2018/06/22/supreme_court_carpenter_location/
>In a decision that will define privacy in the digital age, the US Supreme Court decided 5-4 on Friday that the government needs a warrant to access its citizens' mobile phone location data.
<Written by Chief Justice John Roberts and joined by the four liberal justices, the majority opinion extended the Fourth Amendment on unreasonable search to include location records that mobile phone operators hold on their customers -- a critical distinction that extends privacy protections beyond a physical device.
>Building on another landmark case in 2014 when the court decided [PDF] that a warrant was required to search a mobile phone, the court decided that the "reasonable expectation of privacy" that people have in their "physical movements" should extend to records stored by third parties.
<The case itself concerns Timothy Carpenter who was arrested in 2011 as part of an investigation into armed robberies at Radio Shack and T‑Mobile USA stores in and around Detroit. The police went to mobile phone operators and retrieved four months' worth of location data (known as CSLI or cell site location information) that showed Carpenter was near each of the locations when they were robbed.
The evidence proved crucial to his conviction and 116-year sentence but Carpenter's lawyers argued that the gathering of his location data violated the Fourth Amendment. They lost on appeal with the Sixth Circuit.
>That Sixth Circuit decision has however been both supported and opposed by a number of other appeals courts (the Fifth, Ninth and Eleventh Courts have all decided on similar cases), making it not only a prime candidate for Supreme Court review but also a closely watched case.
<Thanks to its potentially huge implications, the court was careful to stress that its decision was narrow and only covers the specific issue of location data held on an individual by a mobile operator.