ALPR Surveillance: The Supreme Court Says It’s a 'Search.'

Indiana’s current use of automatic license plate readers (ALPRs) is unconstitutional under the Supreme Court’s landmark 2018 ruling, Carpenter v. United States. In that decision, the Court held that long-term government collection of location data constitutes a Fourth Amendment search requiring a warrant. Yet in Indiana today, police departments collect, store, and share millions of license plate scans—data capable of reconstructing the private movements of nearly every driver—without any statewide legal limits.

Eyes Off Indiana is not calling for the removal of ALPR technology. We are calling for sensible, clear, and constitutional regulation that allows public safety to coexist with privacy. The Constitution already provides the framework; the legislature simply needs to apply it.

The Carpenter Precedent: The Expectation of Privacy in Movement

The Supreme Court’s reasoning in Carpenter could not be clearer. Long-term tracking of where individuals travel, even in public, invades core expectations of privacy. The Court’s own words make the case for regulation:

  • Acquisition of location data is a search: “The Government’s acquisition of the cell-site records was a Fourth Amendment search.”
  • The privacy expectation: Individuals maintain a “reasonable expectation of privacy in the whole of their physical movements.”
  • The legal standard: Such surveillance requires a “warrant supported by probable cause.”
  • The unconstitutional power: The Court warned against giving government “unrestricted access to a wireless carrier’s database of physical location information”—a power that must be limited by law.

This is not a theoretical issue. ALPR networks, like cell-site tracking, create a detailed map of citizens’ daily lives—where they sleep, work, worship, and associate. The constitutional limits articulated in Carpenter apply equally to these systems.

The Direct Policy Link: ALPR is the Digital Twin

The parallels between cell-site tracking and ALPR surveillance are undeniable. Both collect continuous, automated records of people's movements across time and space. The following points show how Carpenter’s logic directly supports Eyes Off Indiana’s policy goals:

Strict Retention Limits:
Unregulated data creates an “all-encompassing record of the holder’s whereabouts” and enables “near perfect surveillance” over time—a power the Court explicitly rejected.

Warrantless Access:
Accessing this cumulative data is a constitutional “search.” Obtaining it without a warrant violates the requirement for a “warrant supported by probable cause.”

Transparency and Oversight:
The Court warns against “arbitrary invasions by governmental officials” and demands “obstacles” against “too permeating police surveillance.”

Together, these principles form a clear constitutional directive: the government may not maintain or access vast location-tracking databases without meaningful judicial oversight and strict data retention controls.

The Constitutional Path Forward

The Supreme Court’s majority opinion in Carpenter explicitly stated that the law must “take account of more sophisticated systems.” Indiana’s statutes have not. By failing to regulate ALPR retention and access, our state is ignoring a clear constitutional command.

To remain compliant with federal law and uphold the privacy rights of all Hoosiers, Indiana must enact legislation that:

  • Limits retention of plate data to a short, defined period,
  • Prohibits commercial sharing or resale of ALPR records, and
  • Requires a probable cause warrant for historical data access.

These are not radical reforms—they are the minimum necessary to align Indiana law with the Fourth Amendment.

The Court has spoken. Indiana must act. Join our petition and contact your representative today to demand ALPR regulations that protect both safety and constitutional rights.