MILWAUKEE – On Friday, the American Civil Liberties Union and the ACLU of Wisconsin, along with the Electronic Frontier Foundation, filed a friend of the court brief with the Seventh Circuit Court of Appeals in Chicago arguing that the Fourth Amendment requires law enforcement officials to get a warrant before they may obtain information about the location of a suspect’s cell phone from the suspect’s cell phone company.
Cell phone tracking reveals private and increasingly precise information about our locations and movements. Whenever your phone is turned on—even if you enable its location privacy settings—your cellular provider can determine with remarkable accuracy where your cell phone is. For many of us who carry our phones throughout the day, that also means that our cell phones can reveal where we are virtually all the time. And if the government knows where you are, they often know who you are. Your location can reveal what types of political and religious activities you attend, which doctors you visit, who you spend time with, whether you go to bars or Alcoholics Anonymous, and much more.
And what your cell phone company can learn, police can find out too. In a brief filed yesterday in United States v. Patrick, a case arising in Milwaukee, the ACLU and the Electronic Frontier Foundation argue that any time police seek to use cell phone location data, they should first obtain a warrant from a judge based on probable cause to believe the target is involved in a crime. The requirement that police obtain a warrant ensures that judges can prevent the police from undertaking unjustified fishing expeditions that can reveal intimate details about a person’s activities, associations and beliefs.
The brief also explains that it appears that Milwaukee Police used a cell site simulator, also known as a Stingray, to track the defendant’s phone, but has concealed it from the defense and the courts throughout the case. A previously unpublicized list of 579 investigations  in which the MPD used Stingrays appears to include this case. That list was released  to a privacy activist in response to a public records request last fall. Stingrays mimic cell phone tower antennas and force nearby phones to broadcast their unique serial numbers and other information. The technology raises particularly troublesome concerns under the Fourth Amendment because it not only allows precise tracking of a suspect’s cell phone, but also collects information from bystanders’ phones, blocks those phones from making calls, and identifies and locates phones even inside homes and other private spaces. A probable cause warrant based issued by a fully informed judge should be required before police can use a Stingray.
The brief is at: