# Third Party Doctrine
The Third Party Doctrine, while not a codified U.S. law, is a legally binding precedent stating that any person who shares information with a third party relinquishes their right to privacy over that information. This allows law enforcement and intelligence agencies to access a person's information without a warrant.
# Smith v. Maryland
What is currently known as the third-party docrtine was created from Smith v. Maryland (opens new window). During the case, the court ruled that the government, who created a pen registry with a phone provider to learn the numbers dialed by the provider’s clients, did not violate the Fourth Amendment. This precedent stated that people who voluntarily release their information to a third party should not have an “expectation of privacy” and are not entitled to protections under the Fourth Amendment (Smith v. Maryland 1979, 738).
This is an important legal precedent that the government can use when obtaining information. The precedent allows the government to obtain data on Americans so long as that data is held by a third party, which can occur any time an American accesses the internet. Americans give data to third parties everyday, either through their internet service provider (ISP) or through a technology company like Facebook, Apple, Google, etc.
# Carpenter v. United States
The U.S. Supreme Court ruled in 2017, during Carpenter v. United States (opens new window), that the government requires a search warrant before accessing the cellphone location data of U.S. citizens when that information is givern to a third party (Carpenter v. United States 2017). The court's ruiling focused solely on cell phone location data and did not impact other information, such as internet search history, which can still be obtained through the third party doctrine.
- Smith v. Maryland, 442 U.S. 735 (1979), https://scholar.google.com/scholar_case?case=3033726127475530815 (opens new window).
- Carpenter v. United States, 585 U.S. ___ (2017), https://www.supremecourt.gov/opinions/17pdf/16-402_h315.pdf (opens new window)
- Legalese: The "Third Party Doctrine" and Carpenter v. United States. Georgetown University Law Center, 2018. https://www.youtube.com/watch?v=m8F99BT8QAA (opens new window).