United States v. Sanchez-Jara, No. 17-2593 (7th Cir. 2018)

A federal warrant, issued in July 2015, authorized federal agents to use pen registers, trap-and-trace devices, historical cell-call records, and “electronic investigative techniques” to capture and analyze signals emitted by the subject phones, including in response to signals sent by law enforcement officers to find two cell phones and understand the nature of their owners’ apparently criminal activity. The reference to electronic investigative techniques is a description of a cell-site simulator, a device that pretends to be a cell tower and harvests identifying information, including location data, about every phone that responds to its signals. The Justice Department claims that it discards information about phones other than it is programmed to look for and that it does not receive the contents of any call. To obtain the contents of a call or message, agents would need a warrant under the wiretap statutes, while the 2015 warrant was issued under 18 U.S.C. 2703(d). Defendant argued that 2703(d)’s “reasonable grounds” standard violated the Fourth Amendment’s probable cause standard. The Seventh Circuit declined to address that issue because the 2015 warrant also recited the existence of probable cause. A warrant that authorizes police to follow a particular cell phone adequately describes the evidence to be acquired and is not “open-ended.”