Plate readers in court

Courts across the country are deciding whether police use of automated license plate readers (ALPRs), like the Flock and Axon cameras Altoona runs, is a “search” that needs a warrant. This list collects those rulings and the Supreme Court location-tracking cases they rest on, past and present, with what each decided and where it binds.

Altoona’s own cameras and what the City approved are on the ALPR tracker.

Rulings

What the courts have decided

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Fourth Amendment rulings on plate readers and location tracking

Sort any column. Filter by outcome or court; the filters are kept in the page link.

A row is listed only after its holding was checked against an opinion’s text. Sources and caveats

Read in full means we read the decision itself, at the link in its row. As stated in means we read another court’s opinion that quotes or describes the ruling, named in the row with its pages; those rows are upgraded when the decision itself is read.

Cases are cited by number. Below the Supreme Court, private parties appear by initial only. This is a reading list from public court records, not legal advice.

The third-party doctrine

Records someone else holds

The Supreme Court held in 1976 that a depositor had no legitimate expectation of privacy in his bank’s records of his accounts, which the government got from the bank by subpoena (United States v. Miller). In 1979 it held that recording the numbers dialed from a home phone was not a search, because “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties” (Smith v. Maryland). Courts call this the third-party doctrine: what you share with a bank, a phone company or another business, police can usually get from that business without a warrant.

The Court drew a line in 2018. Historical cell-site records are held by the phone company too, but they are “a detailed and comprehensive record of the person’s movements,” and the Court wrote, “We decline to extend Smith and Miller to cover these novel circumstances” (Carpenter v. United States). Getting them was a search. In 2026 it held the same of a phone’s location history held by Google (Chatrie v. United States).

Plate-reader records sit in the same place. The reads are taken on public roads and stored in a vendor’s system, and courts disagree about which line they fall on; the list above shows each ruling. In one Oklahoma case, police got four months of past turnpike plate-reader records with an administrative subpoena, the third-party route, and the court found no Fourth Amendment violation. In another, a month of a driver’s Flock sightings, searched without a warrant, was held to be a search. Altoona’s plate-reader policy says “Reasonable suspicion or probable cause is not required before using an ALPR” (Policy 424.4(b), quoted in this story’s sources), and the Police Department’s Flock network is configured to share with organizations across the country (the sharing export’s counts).

Analysis / opinion

Doing indirectly what the Fourth Amendment forbids directly

This part is the site’s own view, not a record. The rulings it rests on are linked above and listed on this page.

The Fourth Amendment’s default is a warrant: a judge, probable cause, a named place or person. The third-party doctrine was built for a bank’s ledger and a phone company’s list of dialed numbers. Stretched to a camera network that photographs every passing car and keeps the reads in a company’s cloud, it becomes a way around that default: the government does not search you, it asks the vendor, or it looks at a database it pays the vendor to keep, and calls the result something other than a search.

We think that is the wrong answer, for the reason the Supreme Court gave in 2018. Who holds a record of where you have been does not change what it is. A month of plate reads is a movement history, and a policy that requires no reasonable suspicion or probable cause to search one asks residents to trust a drop-down box in place of a judge. Warrants make police work slower; that cost is the point of the amendment, not a defect in it. As the Court put it about searching a phone seized at an arrest, the answer is “simple—get a warrant” (Riley v. California).

Most courts that have ruled on plate readers so far have disagreed with us, and the list above shows them alongside the rulings that agree. The law is unsettled. That is a reason for Altoona to require a warrant now rather than wait to learn which way it settles.

Legal isn’t the same as right · The Oklahoma ruling beside the City’s own legal reasoning

Reading the list

How to read this list

Search: The court held the police action was a Fourth Amendment search, which generally needs a warrant or an exception.
Not a search: The court held it was not a search.
Did not decide: The ruling turned on something else.
Claim allowed: A civil suit allowed to go forward before any ruling on the merits.
Binds: says which courts must follow the ruling. Altoona is in Iowa, which sits in the federal Eighth Circuit: Iowa’s courts follow the U.S. Supreme Court, and a trial court’s order binds no one outside its own case, though other courts may find it persuasive.
Status: says whether the ruling is final as far as our records show, on appeal, or overruled by a later decision, named in the row.