Third-Party Doctrine / Fourth Amendment
The Doctrine
Information voluntarily given to a third party (bank, phone company, ISP, ad network) carries “no reasonable expectation of privacy.” Government can obtain it without a warrant.
Key Cases
Smith v. Maryland (1979)
Police used pen register to record phone numbers dialed by robbery suspect. No warrant. SCOTUS: no Fourth Amendment violation. Caller “voluntarily conveyed” numbers to phone company and assumed risk of disclosure.
United States v. Miller (1976)
Government subpoenaed bank records (checks, deposit slips) without warrant. SCOTUS: depositor has no Fourth Amendment interest. Documents “contain only information voluntarily conveyed to the banks and exposed to their employees in the ordinary course of business.”
Carpenter v. United States (2018)
SCOTUS 5-4: accessing 7+ days of historical cell site location information (CSLI) is a Fourth Amendment search requiring a warrant. Roberts: CSLI is “detailed, encyclopedic, and effortlessly compiled” providing “near perfect surveillance.”
Carpenter limitations:
- Court explicitly declined to disturb Smith or Miller
- Did not address real-time CSLI, tower dumps, or other techniques
- Applied only to historical CSLI of the scope at issue (127 days)
- Majority: not a “general” revision of the third-party doctrine
Sources
- https://en.wikipedia.org/wiki/Third-party_doctrine
- https://en.wikipedia.org/wiki/Carpenter_v._United_States
- https://epic.org/documents/carpenter-v-united-states-2/
- https://cardozolawreview.com/a-third-party-doctrine-for-digital-metadata/
- https://legaljournal.princeton.edu/carpenter-v-united-states-the-stored-communications-act-the-third-party-doctrine-in-the-digital-age/