The Warrant Question for License-Plate Readers Is 'When,' Not 'If'

A crime analyst who consults for police departments — and served as an expert witness for the Institute for Justice in Schmidt v. City of Norfolk — argues that historical searches of automated license-plate-reader (ALPR) data should require a warrant, and that courts are heading that way regardless. The Norfolk judge ruled that cached ALPR searches weren’t yet an unconstitutional search, but pointedly said ‘not today,’ conceding such surveillance could cross the line as coverage grows. The author’s read of precedent makes that outcome inevitable: Carpenter v. US already forces warrants for cell-site location data because it can reconstruct a person’s entire movements, and Chatrie (geofence warrants) and Beautiful Struggle v. Baltimore (aerial drone imagery) extend the same logic. Once cameras blanket every intersection — which the author expects — plate histories become functionally identical to CSLI.

The piece draws a sharp line between two uses. Active flagging — a camera pinging police when a stolen plate drives past — needs no stored data and raises few concerns. Historical searching — pulling everywhere plate XYZ1000 has been over the last 30 days — lets investigators trace where someone sleeps, works, and repeatedly visits, which is the invasive capability that triggers Fourth Amendment scrutiny. The author contends a warrant requirement for historical lookups wouldn’t meaningfully slow legitimate investigations, while narrow exigent-circumstances exceptions (minutes of recent data, not New Hampshire’s impractical three-minute retention) could cover genuine emergencies like a fresh robbery or a body found roadside.

Notably, the author is bullish on the cameras themselves, calling ALPRs cheap (under $3,000) and a plausible positive return even on a handful of solved cases — unlike overpriced tech such as gunshot-detection systems. The real problem, in his view, is the status quo: minimal or no data retention doesn’t actually prevent illegal searches, the access controls guarding these systems are ‘laughable,’ and short retention windows also hobble legitimate use. His fix is legislative rather than judicial — states should preempt the coming constitutional reckoning by writing warrant procedures into statute, which he argues would leave both police and the public better off.