A recently unsealed application for a search warrant in the US District Court for the Eastern District of Michigan revealed for the first time that federal law enforcement agents are using IMSI catchers, also known as cell site simulators, or more popularly known as Stingrays, to track down illegal immigrants. Stingrays act as fake cell phone towers which mobile devices such as cell phones and tablets are tricked into connecting to as if it were a legitimate cell phone tower. They were originally developed for use by the military and intelligence agencies, but like many other technologies used on the battlefield, it is now being used by domestic law enforcement agencies on American soil. Using these devices, law enforcement is able to triangulate the location of a mobile device and can even intercept data that is being sent and received by the device. Mobile devices can even be hacked by certain IMSI catchers.
Privacy advocates say that use of Stingrays by law enforcement is a violation of privacy rights and the 4th amendment of the US Constitution. When law enforcement deploy a Stingray, every cellular device in the surrounding area connects to it, and so warrants which authorize the use of a Stingray have been compared to illegal general warrants. There is currently free and open source software available which helps users detect and avoid these fake cell phone towers. Law enforcement also requested under the search warrant application that the suspect’s mobile phone provider, T-Mobile, provide information from the E-911 system and from triangulating the suspect through their cell towers to provide a GPS location.
According to the unsealed search warrant application, in March the FBI and Immigration and Customs Enforcement (ICE) used a Stingray in the Detroit metropolitan area to track down a 23 year old suspect from El Salvador who worked in a restaurant and was deported from the United States twice in the past. “This is the first warrant I have seen specifically showing ICE’s use of a cell-site simulator in an immigration enforcement operation,” Nathan Wessler, staff attorney for the ACLU, told The Detroit News. A spokesman for ICE told reporters that the Stingray was a “lawful” and “invaluable” tool used during their investigations.
The Department of Justice (DOJ) only began requiring federal agents to obtain search warrants when using a Stingray in September of 2015, when the DOJ issued a new policy on the use of Stingrays. Prior to the implementation of the new policy, federal agents were not required to obtain a warrant before using a Stingray. It is not known if local and state police assisted the FBI and ICE in their hunt for the immigrant from El Salvador, but it is known that the Michigan State Police have had a Stingray for over a decade. In 2013, the Michigan State Police upgraded their Stingray. State Police in Michigan have used their Stingray well over a hundred times during investigations of various crimes, but never for a terrorism case. Detroit is not a “sanctuary city”, and local officials have stated that they willingly cooperate with federal agencies such as ICE and Customs and Border Patrol, and assist in deportation efforts.
Law enforcement had previously obtained a search warrant for the suspect’s Facebook account. During a search of the suspect’s private messages on Facebook, law enforcement agents discovered the suspect’s cell phone number and the address of where he was staying. In the search warrant application, law enforcement admits that all other cellular devices in the vicinity of the Stingray will be affected. While law enforcement claims in the search warrant application for the Stingray that they would limit and delete any data collected from cellular devices that do not belong to the suspect, and that they would not launch any investigations based on such data without a further court order, it is known that law enforcement sometimes use a technique called “parallel construction”. Parallel construction is a technique used by law enforcement to hide the source of information in an investigation. Information that is obtained illegally by law enforcement is generally not admissible in court, under the “fruit of the poisonous tree” doctrine. Federal agencies such as the DEA and IRS have been trained in how to use parallel construction to hide the source of information when the information is obtained by NSA mass surveillance programs.