## Facts

- Federal investigators linked Timothy Carpenter to a series of armed robberies based in part on information from an arrested suspect.
- The government sought Carpenter’s historical cell-site location information (CSLI) from wireless carriers under the Stored Communications Act (SCA), 18 U.S.C. § 2703(d).
- A court issued § 2703(d) orders compelling disclosure under a “specific and articulable facts” standard, which is less demanding than probable cause.
- Using the orders (not warrants), the government obtained 127 days of CSLI for Carpenter’s phone, totaling 12,898 location points.
- The CSLI data placed Carpenter’s phone near several robbery locations at relevant times and was used at trial.

## Issues

1. Whether the government’s acquisition of long-term historical CSLI from a wireless carrier constitutes a “search” under the Fourth Amendment.
2. If it is a search, whether obtaining CSLI via SCA § 2703(d) orders (without a probable-cause warrant) satisfies the Fourth Amendment.
3. Whether the third-party doctrine applies to historical CSLI such that a user lacks a reasonable expectation of privacy in that data.

## Decision

- The Supreme Court reversed, holding 5–4 that the government’s acquisition of Carpenter’s historical CSLI was a Fourth Amendment search.
- The Court held the government generally must obtain a warrant supported by probable cause before acquiring long-term historical CSLI.
- The SCA § 2703(d) standard was insufficient for obtaining this category of location records.
- The Court limited the third-party doctrine, declining to treat long-term CSLI like traditional business records voluntarily conveyed to third parties.
- The Court characterized the holding as narrow and did not decide questions involving real-time CSLI, tower dumps, conventional surveillance tools, or certain national-security contexts.

## Legal Principles

- Obtaining long-term historical CSLI from a wireless carrier is a Fourth Amendment search because it reveals an extended record of a person’s physical movements.
- A probable-cause warrant is generally required to obtain such CSLI; statutory authorization using a lower evidentiary standard does not by itself satisfy the Fourth Amendment.
- The third-party doctrine does not automatically apply to highly revealing digital location records generated by routine cell-phone operation and held by service providers.
- Fourth Amendment analysis of digital records may account for the quantity, precision, and retrospective reach of the data sought, particularly where it enables extended tracking.

## Conclusion

The Court held that collecting 127 days of historical CSLI without a warrant violated the Fourth Amendment, requiring law enforcement in most cases to secure a probable-cause warrant before obtaining long-term CSLI from wireless carriers and limiting the reach of the third-party doctrine for this form of digital location tracking.


Carpenter v. United States, 138 S. Ct. 2206 (2018)