A federal judge has ruled that a Tulsa County sheriff’s deputy violated the Fourth Amendment when he used Flock license plate reader technology to access weeks of a driver’s travel history, warning that the system risks creating a nationwide “dragnet” of mass surveillance.
U.S. District Judge Sara E. Hill, a Biden appointee, ordered evidence obtained after the search suppressed, finding that the deputy’s use of automated license plate reader data, also known as ALPR data, was an unconstitutional search in violation of the Fourth Amendment.
The case arose after Tulsa County Deputy Sheriff Freddie Alaniz stopped Melisa Kyle while she was driving a car with California plates. Alaniz initially followed Kyle after seeing the out-of-state plate and searched the Flock system for the vehicle.
The search gave Alaniz access to a month of location data showing more than 50 sightings of the vehicle across multiple states. Alaniz then stopped Kyle for following another vehicle too closely and allegedly failing to properly signal lane changes. After questioning her about a short trip to California, Alaniz asked for consent to search her vehicle. Kyle refused. Alaniz then detained her for a drug-sniffing dog, which alerted to the vehicle. Officers searched it and arrested Kyle after finding marijuana.
Kyle challenged the stop, the continued detention, and Alaniz’s use of the ALPR systems.
Hill found that Alaniz had an objectively reasonable basis for the initial traffic stop but concluded that the subsequent ALPR search violated the Fourth Amendment.
The judge acknowledged that people generally do not have an expectation of privacy in their movements on public roads. But she said courts must account for how technology has transformed the government’s ability to track those movements.
“More than 40 years have passed” since the Supreme Court’s 1983 decision in United States v. Knotts, Hill wrote, and courts now face technology “approaching the dragnet type law enforcement practice” that the Supreme Court had warned about.
The difference, Hill said, is that Flock is not merely observing an individual vehicle in real time. The system continuously collects information about vehicles captured by cameras across its network and allows law enforcement to retrieve that information later.
“This is a type of indiscriminate mass surveillance,” Hill wrote. “It is a tool that collects information about all vehicles that pass by any network-connected camera at all times, and it serves up the information to law enforcement on demand.”
She noted that the system available to Alaniz was not limited to stationary cameras. His patrol vehicle itself contributed data to the network.
“It is also no longer difficult to imagine law enforcement using a fleet of drones hovering over an entire city so they don’t miss the movement of a single vehicle,” Hill wrote. “This is not hypothetical catastrophizing.”
The judge said the case demonstrated why courts may need to reconsider how older Fourth Amendment precedents apply as surveillance technology advances.
“No doubt, ALPR technology comes with remarkable benefits that the Court cannot ignore,” she wrote. “But the Fourth Amendment requires courts to draw a line when the cost is too great.”
Hill ultimately ruled that the evidence obtained after Alaniz initiated the ALPR search had to be suppressed under the exclusionary rule.
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“Because the government does not identify any adequate exception to the exclusionary rule,” she wrote, the evidence was suppressed as “fruit of the poisonous tree.”
The ruling comes as courts grapple with whether increasingly sophisticated automated license plate reader networks amount to searches under the Fourth Amendment. Hill noted that neither the Supreme Court nor the 10th Circuit has yet definitively resolved the question, though most courts that have considered the issue have found that ALPR use does not constitute a search.