Essay: Historical License Plate Reader Searches Should Require a Warrant

Crime analyst and consultant Andrew Wheeler published an essay on August 12, 2026 arguing that historical searches of automated license plate reader (ALPR) data should require a warrant. Wheeler, who works with police departments, served as an expert witness for the Institute for Justice in Schmidt v. City of Norfolk. In his view the question is not whether such searches will eventually need judicial approval, but when.

Legal precedent points one way

Wheeler builds the argument on existing US case law. In Carpenter v. United States, the Supreme Court required police to obtain a warrant for cell-site location information held by carriers, on the grounds that comprehensive location data reveals the whole of a person's movements. Later rulings applied similar logic to geofence warrants in Chatrie and to historical aerial surveillance imagery in Beautiful Struggle v. Baltimore. If ALPR cameras ever cover every intersection, Wheeler writes, the data would raise the same privacy concerns and courts will require a warrant.

Active alerts versus historical searches

The essay draws a sharp line between real-time operation — a stolen plate pinging a patrol car — and retroactive queries such as where plate XYZ1000 was over the last 30 days. The latter can reconstruct a person's route, frequent visits and, in practice, where they sleep. Wheeler considers a few hours of cached data reasonable under exigent circumstances, for example after a robbery, but calls New Hampshire's three-minute retention far too short. Virginia, where the Norfolk case was heard, set a statewide 21-day standard; other states mandate roughly 30 days or leave retention to individual agencies.

Retention limits do not stop abuse

Wheeler argues that deletion rules are presented as abuse prevention but fail at it. In documented misuse cases, officers searched the same plate hundreds of times — something a 20-day purge cannot prevent, since anyone can simply repeat the query every three weeks. At the same time, deletion undermines legitimate work: murder investigations routinely take more than 30 days, and defence teams need the data for exculpatory checks. In the Norfolk case, search justifications sometimes read protest, and Raleigh police only ran their first audit after journalist Tyler Dukes requested the results.

What smart regulation looks like

His proposal: state statutes requiring a warrant for historical ALPR searches outside a short real-time window; clear penalties such as dismissal and a permanent ban from the system; automatic flags when the same plate or camera is searched twice within two days; and independent audits by a state attorney general's office or a criminal justice agency rather than by vendors or departments themselves. ALPR cameras cost well under $3,000 each and likely pay for themselves, he concludes, so the warrant requirement is a reasonable trade-off rather than a barrier to policing.