Fourth Amendment Law and Third-Party Doctrine After Carpenter v. US

By Sean Larner, CLS ’20

A few months ago, the Roberts Court decided a landmark case, Carpenter v. US, that represents the Court’s first meaningful step to protect American privacy interests against government intrusion in the digital age.

Evidentiary exclusion is the only reliable bulwark American citizens have against illegal government intrusion.  However, since the landmark rulings in Weeks v. US, 232 U.S. 383 (1914), where the Supreme Court ruled that evidence obtained pursuant to a Fourth Amendment violation was subject to exclusion, and Mapp v. Ohio, 367 U.S. 643 (1961), which applied the exclusionary rule to the states through the Fourteenth Amendment, the Burger, Rehnquist and especially the Roberts Courts have chipped away at the initially expansive holdings in Weeksand Mapp. Since Mapp, subsequent Courts have prohibited exclusion for good-faith violations, lack of “standing” (which is more substantive than procedural in Fourth Amendment law), knock-and-announce violations, knowing exposure to third-parties, along with grand jury proceedings altogether. But on June 22, 2018, something changed. Amid a spate of conservative decisions in the 2017-2018 Term, the Supreme Court made a shocking announcement in Carpenter v. US, 267 U.S. 132 (2018), that the government’s acquisition of cell-site information location (CLSI), which is the cell phone data obtained from nearby cell towers used to triangulate cell phone locations, constituted a “search” within the Fourth Amendment and was thus susceptible to the Warrant Requirement.

Ever since the decision in Katz v. US, 389 U.S. 347 (1969), over a half-century ago, expanded the scope of Fourth Amendment protections in light of technology’s inexorable advance, there has been a perhaps unanticipated contingency: the birth of the “knowing exposure” doctrine. Under the knowing exposure doctrine, any information shared voluntarily with a third party, no matter how sensitive, from telephone records to bank records, are not within the ambit of the Fourth Amendment. Because an individual “voluntarily” shared his bank records with the bank, government acquisition of those materials does not constitute a “search.” Under the capacious third-party doctrine, a warrant is not needed to compel production––just a subpoena. Katz and the third-party doctrine met a notable limitation in Carpenter.

Timothy Carpenter was convicted of leading a string of armed robberies in multiple states. Under the authority of the Stored Communications Act, the FBI obtained Carpenter’s CLSI, which put him within proximity of four of the robberies. All the FBI needed to prove to get a magistrate judge to sign off on a subpoena was the relevance of the evidence to a criminal investigation, as opposed to the more onerous probable cause requirement needed to obtain a search warrant. The CLSI evidence was adduced at trial and the defense counsel’s objection was overruled. Carpenter was convicted and sentenced to 116 years in federal prison.

In a shocking break from the Court’s longstanding adherence to the third-party doctrine, Chief Justice John Roberts wrote for the majority that CLSI is by its nature a unique type of record that implicates Fourth Amendment concerns about “arbitrary police power” and “too permeating police surveillance,” recognizing that cell phones today have virtually become a part of the human anatomy. Roberts indicated that there may be limitations to the third-party doctrine in the digital era when the type of record at issue is collected automatically and is extraordinarily comprehensive in its reach into the intimate details of a person’s life. The new multifactor analysis under Carpenterconsiders the intimacy, comprehensiveness, expense, retrospectivity and voluntariness of disclosure to third parties, in order to avoid ‘too permeating a police surveillance’ and ‘arbitrary police power.’ The biggest hole in Carpenter, however –– as Justice Kennedy rightly points out in his dissent –– is that private companies like AT&T still have unfettered access to all of our ostensibly private information. Indeed, they sell it to other businesses for billions.

Although it’s unclear how this groundbreaking development in Fourth Amendment law will play out in the lower courts, the CarpenterCourt changed the contours of the third-party doctrine, protecting the CLSI of all Americans from unwarranted government intrusion.