The Department of Homeland Security Office of the Inspector General has concluded that both the Secret Service and U.S. Immigration and Customs Enforcement sometimes employed the use of cell-site simulators (CSS) without obtaining proper authorization.
A CSS functions as a fake cell phone tower and is used trick known cellular devices into transmitting to the CSS as a means of locating them. The Department of Justice noted that they do not function as a GPS tracker and are only able to determine signal strength and general location.
Both ICE HSI and the Secret Service the technology to locate the subjects of their investigations in real time. Using CSS, however, requires a court order, something the IG determined the federal agencies did not always obtain. Exemptions do exist for both "exigent" and "exceptional circumstances."
"[T]he Secret Service and ICE HSI [Homeland Security Investigations] did not always obtain court orders required by CSS policies and Federal statute when using CSS during investigations that included exigent circumstances," the IG report read. "This occurred for two reasons. First, CSS policies do not include sufficiently detailed guidance on working with external law enforcement agencies."