Cell phones perform their wide and growing variety of functions by continuously connecting to a set of radio antennas called “cell sites.” Each time a phone connects to a cell site, it generates a time stamped record known as cell site location information (CSLI). Wireless carries collect and store this information for their own business purpose. A person’s phone number and phone records may then be used to pinpoint their location over a specific time period.
The question is whether the government may seize the phone records without fist obtaining a warrant supported by probable cause.
The answer as seen in Carpenter v. United States is yes.
In Carpenter, the government acquired the defendant’s phone records via a court order (as opposed to a probable cause warrant) to pinpoint his location and show he (or his phone) was at the location where several robberies took place.
On appeal, the United States Supreme Court, in a 5-4 decision ruled a person has an expectation of privacy in the wealth of information provided by cell sites, including their location, and the 4th Amendment applies. As such, absent a lawful warrant supported by probable cause, the phone records were obtained unlawfully and should not have been used at trial.