Amid growing privacy concerns over Flock cameras, a Texas man has asked a federal appeals court to toss out his armed robbery conviction and 60-year prison sentence, arguing that the AI-powered camera system gives law enforcement more surveillance power than the Constitution allows.

Police used Flock cameras to link Charles Brownlee to five armed robberies across several Dallas-Fort Worth suburbs in 2024 by compiling a “pattern of life” that traced his travels along North Texas roads monitored by Flock’s vehicle-scanning devices.

The data gathered is so extensive and invasive that police should be required to obtain a search warrant, approved by a judge, before rifling through Flock data, Brownlee’s lawyers argue.

“No mortal human has ever possessed” such an ability to effortlessly and immediately reconstruct any person’s movements, Brownlee lawyer Matthew Wright told the 5th U.S. Circuit Court of Appeals during oral arguments on Oct. 5.

“I’m not sure that the full capabilities of these systems have been either revealed or litigated,” Wright told the three-judge panel in New Orleans.

Flock’s software logs every vehicle that passes any of the estimated 13,000 cameras in Texas, giving law enforcement access to a powerful tracking system. The devices are a hotly contested new tool that police praise as equivalent to DNA testing in its ability to revolutionize policing and improve public safety.

Before his trial, Brownlee asked the federal judge to block prosecutors from using the Flock data as evidence, arguing his vehicle was unlawfully tracked without a search warrant. U.S. District Judge Terry Means declined, Brownlee was convicted and defense lawyers responded by asking the 5th Circuit Court to set aside his verdict.

“Flock’s surveillance database indiscriminately collects a vast trove of locational data about Americans who drive or ride in cars,” Brownlee’s lawyers told the 5th Circuit Court in a legal brief. “By capturing, storing, retrieving, and indexing this data, Flock gives police the power to find almost anyone and reconstruct their movements.”

License plate reading cameras have been available for decades, but what sets Flock apart is the ability for officers to scan data compiled by other police departments to create software-driven maps of a vehicle’s movements.

The Fourth Amendment protects against unlawful search and seizure, often by requiring law enforcement to have some level of probable cause that a crime has been or will be committed, as well as a search warrant approved by a judge. Data from the Flock system can be accessed with the push of a few buttons, and currently there is no legal requirement to first obtain a search warrant.

Police perform a search, triggering Fourth Amendment protections, when they violate a person’s reasonable expectation of privacy, Brownlee’s lawyers argued.

The 5th Circuit Court earlier this year ruled that some use of automated license plate readers is not a Fourth Amendment violation.

In that case, a Mississippi man was stopped after passing a Flock camera that alerted a nearby officer, who pulled him over and saw an illegally modified handgun in the vehicle. The appeals court ruled in March that the search was acceptable because it involved a single camera that was incapable of tracking the “whole of an individual’s physical movements, much less for a very long period.”

The ruling, however, acknowledged that roadside camera systems give “the government to access an historical record for some time, and that type of retrospective data can allow police to travel back in time to retrace a person’s whereabouts without needing to know in advance whether they want to follow a particular individual, or when.”

Brownlee’s lawyer argued that the search used in Texas went much farther.

“What you have here [is] in the space of two and a half hours, they’re able to find literally a needle in a haystack, but they didn’t even know the needle they were looking for when they started looking,” Wright said.

In addition, living in Texas — especially in the sprawling Dallas-Fort Worth area — frequently requires a vehicle, making Flock cameras “more inescapable than cell phone location tracking,” a type of search the U.S. Supreme Court recently affirmed is protected by the Fourth Amendment, Brownlee’s lawyers told the appeals court in a legal brief.

“While individuals can, theoretically, choose not to carry a cell phone, driving is effectively mandatory for most Americans to participate in modern life,” the brief said.

Justice Department attorney Michael Weisbuch argued that the March ruling justified the search for Brownlee’s vehicle because Flock’s data is “episodic,” or based on photos taken from individual cameras. That means Flock photos and data are not actively tracking vehicles but are instead providing pieces of evidence gathered along public roads, where motorists have no legal expectation of privacy, he said.

Chief Judge Jennifer Walker Elrod asked Weisbuch how many Flock cameras would be needed to elevate episodic captures into a more constant mode of surveillance — especially, as she said, the cameras are “soon to be” on every street corner.

“We’re trying to figure out whether or not we’re there [in the Brownlee case], and when is the tipping point,” Elrod said.

Weisbuch responded that Flock cameras are at the center of a “major policy debate” nationwide, and defining how many cameras constitutes constant surveillance is a question better suited for legislators.

“The political process is a serious check on that [hypothetical] ever coming to fruition, and I think a better check than an erroneous extension of Fourth Amendment,” he said.

Several Texas lawmakers, raising Fourth Amendment concerns, say they intend to file bills restricting or banning the use of Flock cameras and similar automated license plate readers in the 2027 legislative session. They include Sen. Lois Kolkhorst, who in late August promised legislation to reign in the currently unregulated use of the cameras.

“My legislative actions on this issue will be founded in the Fourth Amendment,” the Brenham Republican wrote in an op-ed shared through social media.

U.S. Rep. Keith Self, a McKinney Republican, has also proposed legislation to require federal agencies to obtain warrants before accessing Flock camera data.

In a legal brief to the 5th Circuit Court, federal prosecutors argued that Flock cameras were not the pervasive tool Brownlee described them to be. Other evidence — including traditional surveillance cameras and cell phone data — were equally useful in finding Brownlee, they said.

“Brownlee can only make hyperbolic arguments about a future Panopticon,” prosecutors wrote. “Plainly, the [license plate reading] cameras in the DFW metroplex do not subject anyone to observation ‘during every instant of time.’”

During oral arguments, Weisbuch also argued that Brownlee lacked the legal standing to challenge the Flock search because he neither owned nor drove the car tracked by police, but was a passenger.

“When the police did this database query, they didn’t learn anything about Mr. Brownlee. It was his sister’s car,” Weisbuch said. “They had no reason to think that he, in particular, was in the car. And it seems like that should affect the analysis somewhat.”

The 5th Circuit Court has no deadline to issue its ruling.

In a similar case, U.S. District Judge Sara Hill in Oklahoma ruled Oct. 1 that use of Flock data violated the Fourth Amendment in a case involving a drug arrest — seemingly the first ruling of its kind.

A Tulsa County sheriff’s officer used camera images to track Melisa Kyle’s travels between Missouri and California. The officer began following Kyle’s car — and searched it on the Flock system — “for no apparent reason other than the fact that it had a California license plate,” Hill wrote in her ruling.

After reviewing the Flock records showing the interstate trip, Kyle was pulled over and police found 91 pounds of methamphetamine in her car. Hill suppressed the drug evidence, saying it stemmed from an unconstitutional Flock search. That ruling has not yet been appealed.