Cell-site simulators are devices used by law enforcement. In response to the signals emitted by a cell-site simulator, cellular devices in the proximity identify the simulator as the most attractive cell tower in the area and transmit signals to the simulator that identify the device. Using these simulators, investigators can locate cellular devices whose unique identifiers are already known to law enforcement, or determine the unique identifiers of an unknown device by collecting limited signaling information from devices in the simulator user’s vicinity. -- It has been a subject of debate whether the use of cell-site simulators by the government requires a warrant supported by probable cause. In September 2015, the Justice Department released a policy requiring federal investigators to obtain a warrant prior to employing a simulator, except under exceptional circumstances. -- Is there a Fourth Amendment reasonable expectation of privacy in the data collected by cell-site simulators? Who is in the best position to establish limits in this area (if any), Congress or the courts? Should investigators be permitted to use simulators, even with a warrant? -- Featuring: Howard W. Cox, Adjunct Professor, George Washington University and Prof. Brian L. Owsley, Assistant Professor of Law, UNT Dallas College of Law.