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Case summary · U.S. Supreme Court

Carpenter v. United States

Published · Last reviewed · By Editorial team · Not attorney-reviewed

Court
U.S. Supreme Court
Decided
Citation
585 U.S. 296 (2018); 138 S. Ct. 2206
Docket
No. 16-402
Binding in
Federal (nationwide)
Status
Held

Read the opinion (No. 16-402 · June 22, 2018)

What the court held, in plain English

The government’s acquisition of historical cell-site location records is a Fourth Amendment search, and it must generally obtain a warrant supported by probable cause first. The Court called its decision narrow. It didn’t decide anything about license plate readers or “conventional surveillance techniques and tools, such as security cameras.”

The question

Does the government conduct a Fourth Amendment search when it obtains a person’s historical cell-site location information (CSLI) from wireless carriers?

The facts

Investigating a string of robberies, prosecutors used court orders under the Stored Communications Act, which required less than probable cause, to obtain Timothy Carpenter’s cell-site records. The carriers produced 12,898 location points over 127 days, an average of 101 per day. The records helped convict him. The Sixth Circuit held he had no reasonable expectation of privacy in records held by his carriers.

What the court held

In a 5–4 opinion by Chief Justice Roberts, the Court reversed. It held that “the Government’s acquisition of the cell-site records was a search,” and that “the Government must generally obtain a warrant supported by probable cause before acquiring such records.” Mapping a phone’s location over 127 days, the Court said, “provides an all-encompassing record of the holder’s whereabouts.”

Justices Kennedy, Thomas, Alito and Gorsuch dissented.

Why it matters for license plate readers

Carpenter is the decision most often cited by analogy in ALPR challenges, because a large ALPR network can also build a long-term record of where someone travels. Whether ALPR data is similar enough to cell-site data to require a warrant is a question Carpenter didn’t answer, and courts are still working through it. Massachusetts’s high court compared four bridge cameras to “only two cellular telephone towers” in Commonwealth v. McCarthy.

What it didn’t decide

The Court said: “Our decision today is a narrow one.” It did not:

  • Decide real-time CSLI or “tower dumps”
  • “call into question conventional surveillance techniques and tools, such as security cameras”
  • Address other business records that might incidentally reveal location
  • Decide “whether there is a limited period for which the Government may obtain an individual’s historical CSLI free from Fourth Amendment scrutiny”
  • Address license plate readers at all

Later history

Carpenter remains good law. Lower courts continue to apply it to new kinds of location data, with differing results.

One ruling doesn’t settle every case. A decision binds courts within its jurisdiction, and outcomes depend on the facts. See how we summarize cases in our editorial standards.

Sources

  1. OpinionCarpenter v. United States, slip opinion, Supreme Court of the United StatesNo. 16-402 · June 22, 2018