# ALPR Fourth Amendment Law Is Fact-Bound and Unsettled No controlling U.S. Supreme Court or Eighth Circuit decision in this audit creates a categorical rule for a modern, networked ALPR system. The cases instead turn on what was collected, for how long, at what density, whether the government accessed an aggregated record, and what procedural question the court actually decided. ## Controlling location-privacy principles are not ALPR holdings *Carpenter v. United States* holds that accessing seven days of historical cell-site location information is a search and that third-party possession does not eliminate the protected privacy interest. The Court expressly did not decide conventional cameras or every shorter-term technology. (primary public record, [Carpenter v. United States](../../web%20archive/2026-08-10/supremecourt.gov/carpenter-v-united-states-585-u-s-296-2018.md)) *Chatrie v. United States* holds that police acquisition of Google Location History is a search even for a limited duration and notwithstanding third-party possession. It is a cell-phone-location case, not an ALPR case; separate-opinion particularity reasoning is not treated here as the majority holding. (primary public record, [Chatrie v. United States](../../web%20archive/2026-07-20/supremecourt.gov/chatrie-v-united-states-25-112.md)) *United States v. Knotts* found no search in monitoring one public-road beeper journey, but expressly reserved dragnet-type surveillance. The Eighth Circuit's short-duration GPS cases likewise carry material limits: *Dewilfond* involved owner consent and two days of real-time public-road tracking, while *Marquez* predates *Jones* and *Carpenter* and involved a passenger without a sufficient connection to the vehicle. (primary public record, [United States v. Knotts](../../web%20archive/2026-08-10/govinfo.gov/united-states-v-knotts-460-u-s-276-1983.md)); (primary public record, [United States v. Dewilfond](../../web%20archive/2026-08-10/ecf.ca8.uscourts.gov/united-states-v-joshua-dewilfond-54-f-4th-578-8th-cir-2022.md)); (primary public record, [United States v. Marquez](../../web%20archive/2026-08-10/ecf.ca8.uscourts.gov/united-states-v-marquez-605-f-3d-604-8th-cir-2010.md)) ## ALPR decisions are bounded by their records - The Fifth Circuit's *United States v. Porter* held that ten periodic public-road ALPR detections did not amount to a search and that a verified active-warrant hit supported the stop. The opinion did not decide dense, prolonged, nationwide, passenger-level, or comprehensive tracking. (primary public record, [United States v. Porter](../../web%20archive/2026-08-10/ca5.uscourts.gov/usa-v-porter-no-25-60163-5th-cir-mar-17-2026.md)) - Virginia's unpublished *Commonwealth v. Church* held that access to three images over about seven minutes was not a search. It is nonprecedential and does not decide long-duration or networked collection. (primary public record, [Commonwealth v. Church](../../web%20archive/2026-07-20/vacourts.gov/commonwealth-v-church-0737-25-1.md)) - The published Virginia decision in *Robinson* held that a targeted two-hour, vehicle-attribute search of a 30-day, 172-camera system did not reveal a comprehensive chronicle on that record. It rejected speculation about capabilities not presented, not every broader query. (primary public record, [Robinson v. Commonwealth](../../web%20archive/2026-08-10/vacourts.gov/eddie-eugene-robinson-v-commonwealth-of-virginia-no-1912241-va-ct-app-apr-7-2026.md)) - *Schmidt v. City of Norfolk* found standing to challenge collection and storage but not an unperformed query, then granted the city summary judgment on a developed record of 176 cameras, generally 21-day retention, and sparse captures that did not catalog the whole of the plaintiff's movements. The verified appeal remained unresolved at the audit cutoff; the decision does not bless denser or more complete systems. (web research 2026-07-20, [Schmidt merits order](../../web%20archive/2026-07-20/cases.justia.com/schmidt-v-city-of-norfolk-document-191.md)) ## Aggregated surveillance supplies counterauthority The Fourth Circuit en banc held in *Leaders of a Beautiful Struggle* that accessing retained citywide aerial data capable of reconstructing the whole of people's movements was a search. Labor-intensive inference and integration with other systems did not remove the constitutional problem. That program was not ALPR, but its aggregation analysis prevents short-trip ALPR cases from becoming a universal rule. (primary public record, [Leaders of a Beautiful Struggle v. Baltimore Police Department](../../web%20archive/2026-08-10/ca4.uscourts.gov/leaders-of-beautiful-struggle-v-baltimore-police-department-2-f-4th-330-4th-cir-2021.md)) ## Consequence for the Arkansas investigation The Arkansas record must be developed system by system: camera density and placement, capture frequency, retention, network reach, query duration and parameters, vehicle-versus-person association, integration with other datasets, and whether challenged data were merely collected, stored, or actually accessed. Capability alone does not prove a search, and a narrow no-search decision does not validate a statewide or aggregated network. ## Open questions - What specific query, time span, geographic scope, and returned path would an Arkansas claimant challenge? - How complete is the vehicle-movement chronicle created by owned cameras plus shared networks? - What happened in the unresolved *Schmidt* appeal after the verified audit cutoff? - Which facts would distinguish collection/storage standing from standing to challenge a query that was never run?