Require Police to Get a Warrant to Search ALPR Data

This post was co-written by Andi Cao, an EFF legal intern.

Automated license plate readers (ALPRs) are mass surveillance. They photograph every passing car and log where and when it was captured, building a searchable record of where nearly everyone drives. Cities should not buy them, and cities that already have them should shut them down.

Where these systems still operate, courts and state legislatures must reduce their harms by (among other things) requiring police to get a warrant before searching stored ALPR data. A warrant requirement would not make mass surveillance acceptable, but it would require police to justify a search to a judge before accessing records of people’s movements. Without this independent judicial check on police power, officers have been searching this data for improper reasons (many exposed by EFF) that violate our fundamental rights.

A warrant requires a judge to find probable cause and specificity—many warrantless police searches of ALPR data lack both. Officers have searched this data to profile Romani people, monitor protesters, investigate an abortion, find immigrants for deportation, track a man who complained about a deputy, stalk romantic partners, and even for no stated reason beyond “LMAO.” A warrant requirement would force law enforcement to justify these searches before accessing sensitive location records, not leave the people they target to discover and challenge the abuse after the harm is done.

Warrants are a check on police power. Before officers can search a person or their property, the Fourth Amendment requires them to convince a neutral judge, under oath, that probable cause exists, meaning a fair probability the search will turn up evidence of a crime. The warrant must also describe with particularity what will be searched, so police cannot go on a fishing expedition. Critically, the officer who wants to search is not the person who decides whether the search is justified.