Chief Justice Roberts continued: Tracking a person’s past movements through CSLI partakes of many of the qualities of GPS monitoring considered in Jones—it is detailed, encyclopedic, and effortlessly compiled. At the same time, however, the fact that the individual continuously reveals his location to his wireless carrier implicates the third-party principle of Smith and Miller. Given the unique nature of cell-site records, this Court declines to extend Smith and Miller to cover them.
A majority of the Court has already recognized that individuals have a reasonable expectation of privacy in the whole of their physical movements. Allowing government access to cell-site records—which “hold for many Americans the ‘privacies of life,’” Riley v. California, 573 U. S. ___, ___—contravenes that expectation. In fact, historical cell-site records present even greater privacy concerns than the GPS monitoring considered in Jones: They give the Government near perfect surveillance and allow it to travel back in time to retrace a person’s whereabouts, subject only to the five-year retention policies of most wireless carriers. The Government contends that CSLI data is less precise than GPS information, but it thought the data accurate enough here to highlight it during closing argument in Carpenter’s trial. At any rate, the rule the Court adopts “must take account of more sophisticated systems that are already in use or in development,” Kyllo, 533 U. S., at 36, and the accuracy of CSLI is rapidly approaching GPS-level precision.
The Government contends that the third-party doctrine governs this case, because cell-site records, like the records in Smith and Miller, are “business records,” created and maintained by wireless carriers. But there is a world of difference between the limited types of personal information addressed in Smith and Miller and the exhaustive chronicle of location information casually collected by wireless carriers. The third-party doctrine partly stems from the notion that an individual has a reduced expectation of privacy in information knowingly shared with another. Smith and Miller, however, did not rely solely on the act of sharing. They also considered “the nature of the particular documents sought” and limitations on any “legitimate ‘expectation of privacy’ concerning their contents.” Miller, 425 U. S., at 442.
The counter argument to the “third party doctrine” is that while cell-site information might be knowingly shared, it is not voluntarily shared. This is because all of the wireless carriers operating in the United State retain cell-site information for at least one year. See https://articles.forensicfocus.com/2017/04/18/cellular-provider-record-retention-periods/. Thus, if you use a cell phone, you are forced to share this information with third parties. Moreover, most people are forced to carry cell phones as part of their job duties.
