United States v. Ammons, 207 F. Supp. 3d 732

Playpen was a Tor hidden-service website distributing child pornography; the FBI seized its server and operated it temporarily from the Eastern District of Virginia.
The FBI obtained an NIT warrant from an Eastern District of Virginia magistrate judge to deploy code on Playpen that would cause visiting computers to transmit identifying data (IP, OS, host name, MAC, etc.) to the FBI.
The NIT identified a Playpen user tied to an IP address that, via subpoena to the ISP, traced to Dennis Ammons' home in the Western District of Kentucky.
The FBI then obtained a residential search warrant for Ammons' home; execution of that warrant produced admissions and additional child-exploitation evidence.
Ammons moved to suppress all evidence derived from the NIT, arguing the NIT warrant was void because the issuing magistrate lacked authority under 28 U.S.C. § 636 and Fed. R. Crim. P. 41(b).
The district court concluded the NIT deployment was a Fourth Amendment search, the issuing magistrate lacked jurisdiction so the NIT warrant was void ab initio, but suppression was not required because the agents reasonably relied on the warrant (good-faith exception).

Issue	Ammons' Argument	Government's Argument	Held
Whether deploying the NIT was a Fourth Amendment "search"	NIT intruded on reasonable privacy in home computer and its contents	NIT merely captured nonprivate metadata like IP address (no protected expectation)	The NIT deployment was a Fourth Amendment search of Ammons' computer
Whether the magistrate judge who issued the NIT warrant had authority under §636/Rule 41	Buchanan lacked authority because the property to be searched (remote computers) were outside her district	Rule 41(b)(1),(2),(4) empower magistrate to issue such warrants (or district had strongest connection)	Magistrate Judge Buchanan lacked authority; the NIT warrant was void ab initio
Whether the NIT deployment (and seizure of data) was justified by exigent circumstances	No exigency—FBI had custody of server and operated it for ~2 weeks, so no immediate necessity	Ongoing child abuse and need to identify users justified prompt action	No exigent-circumstances exception; the warrantless search violated the Fourth Amendment
Whether suppression is required despite the warrant being void ab initio	Good-faith exception unavailable for a warrant issued by someone lacking authority; suppression required	Good-faith exception applies because agents reasonably and objectively relied on the magistrate's warrant; no deliberate police or judicial misconduct	Good-faith exception applies; suppression denied (agents acted in objectively reasonable good faith)

Kyllo v. United States, 533 U.S. 27 (search-question framework for Fourth Amendment) (thermal-imaging precedent for defining searches)
Katz v. United States, 389 U.S. 347 (1967) (reasonable expectation of privacy test)
United States v. Master, 614 F.3d 236 (6th Cir. 2010) (good-faith exception can apply even when warrant is void ab initio)
Herring v. United States, 555 U.S. 135 (2009) (exclusionary rule deterrence balancing; good-faith limits)
Illinois v. Gates, 462 U.S. 213 (probable cause/affidavit standard and magistrate review principle)
United States v. Leon, 468 U.S. 897 (1984) (establishing the good-faith exception to exclusionary rule)
Hudson v. Michigan, 547 U.S. 586 (2006) (suppression is not automatic; exclusion as last resort)
United States v. Krueger, 809 F.3d 1109 (10th Cir.) (discussion of jurisdictional limits on magistrates and void warrants) (Gorsuch concurrence noted)
United States v. Carpenter, 819 F.3d 880 (6th Cir. 2016) (noting limits on expectation of privacy for certain metadata; used in analysis)