(CN) - Pushing the Seventh Circuit to make strides in data privacy, civil rights groups say police likely hid their warrantless use of a StingRay to track a suspect's location via his cellphone.
The Electronic Frontier Foundation made the argument in a friend-of-the-court brief joined by the American Civil Liberties Union and the ACLU of Wisconsin.
Their Jan. 22 filing urges the federal appeals court in Chicago to suppress evidence against Damian Patrick, a 27-year-old charged in Wisconsin with being a felon in possession of a firearm.
Tracking Patrick's location via his cellphone data, police allegedly found the man in a car with a gun at his feet.
Patrick says the warrantless tracking violated his Fourth Amendment rights, but U.S. District Judge Rudolph Randa in Milwaukee refused to suppress the evidence last year.
Civil rights groups are joining Patrick's appeal since his case represents the first time the Seventh Circuit "is considering whether citizens have an expectation of privacy in real-time cellphone location records,'' EFF senior staff attorney Jennifer Lynch said in a statement.
In Patrick's case, the government claimed in affidavits that it obtained cellphone location information about the suspect from Sprint by requesting "a pen register/trap and trace order."
The EFF and ACLU nevertheless argue that "the government may instead have located the defendant using a cell-site simulator, commonly known as a StingRay."
A StingRay device acts like a cellphone tower, forcing nearby cellphones to connect to it and to provide data, including what phone numbers are called and the duration of the call.
Indeed, Milwaukee Police Department logs released in response to a public-records request state "that the agency used a StingRay to locate a 'fugitive' 'related to [an] FBI roundup' on Oct. 28, 2013," the day Patrick was apprehended, according to the brief.
Furthermore, the magistrate overseeing Patrick's case noted in one order that "the government failed to disclose in any of its reports that it had located the defendant by tracking his cellphone, and the defendant did not learn about this fact until an evidentiary hearing on February 4, 2014," according to the brief.
The EFF and ACLU note that law enforcement agencies have been using such "privacy-invasive devices," but that governmental secrecy ensures such technology faces "little to no oversight from legislative bodies or the courts."
The brief points a nondisclosure agreement the Milwaukee Police Department signed with the FBI regarding the use of StingRay technology, agreeing "to not, in any civil or criminal proceeding, use or provide any information concerning the Harris Corporation wireless collection equipment/technology [StringRay]... beyond the evidentiary results obtained through the use of the equipment/technology."
If the government did in fact use StringRay technology, "this lack of candor with the lower court and with the Defendant would be sufficient grounds to invalidate the order and to suppress the evidence gathered as a result of the unlawful search," according to the brief.
Among Seventh Circuit jurisdictions, "Wisconsin, Indiana, and Illinois all now require police to get a warrant to conduct real-time cellphone location tracking," the amicus brief states.
The EFF and ACLU also note that nine other states - California, Maine, Maryland, Minnesota, Montana, New Hampshire, Utah, Virginia, and Washington - also require a warrant to conduct real-time cellphone tracking.
Quoting the U.S. Supreme Court's 2014 holding in Riley v. California, the EFF and ACLU note that there is a simple answer when it comes to what police must do to obtain location data generated by cellphones: "get a warrant."