Ark investigation: Follow-up audit finds far broader access to Tiburon license-plate data

Paper identifies 16,029 questionable searches by 41 agencies — largely missed by town — as Flock changes conceal records and town expands surveillance with two more cameras

Tiburon has installed two new Flock automated license-plate-reading cameras in the downtown Tiburon Boulevard median in front of the library. Some 41 California law-enforcement agencies conducted 16,029 potentially illegal searches of Tiburon's camera logs from July through December, according to a new audit by The Ark. These findings come as Atlanta-based Flock Safety has implemented system updates that effectively conceal illegal searches from clients and the public. (Francisco Martinez / The Ark)

A new audit by The Ark has found 41 California law-enforcement agencies conducted 16,029 potentially illegal searches of Tiburon’s automated license-plate logs from July through December — 18 more agencies than the Police Department disclosed after its own audit of the same period. The department’s keywords would have missed nearly 97% of searches.

The findings come as its vendor, Atlanta-based Flock Safety, has implemented system updates that effectively conceal illegal searches from clients and the public, making already inadequate self-audits even less effective, critics say. And the company is now stripping required data from audit records, a move that immediately puts Tiburon, Belvedere and other California clients in violation of state law, according to the Electronic Frontier Foundation and American Civil Liberties Union.

Meanwhile, Tiburon has further expanded surveillance, adding its first two cameras downtown.

The Ark’s initial investigation, published in February, found that nine agencies had conducted 475 searches from May through August citing federal agencies, including the FBI, DEA and U.S. Marshals Service. California’s Senate Bill 34, implemented in 2016, prohibits any sharing of camera data with private, out-of-state and federal agencies to protect Californians’ privacy. SB 54, which took effect in 2018, broadly bars state and local agencies from using their resources for federal immigration enforcement.

The paper’s monthslong inquiry prompted Police Chief Michelle Jean to conduct her own audits of the July to December period. Days before publication, she acknowledged 23 agencies had made potentially illegal searches — including searches involving federal immigration agencies — and announced a new protocol to contact those agencies to explain the searches or lose access.

Records subsequently obtained by The Ark show Jean sent letters to 21 agencies on Jan. 15, with a 30-day response deadline that expired after the paper’s February report, and she phoned one more. As The Ark went to press March 23, access for 10 of those agencies had been revoked.

Of the 41 agencies identified by The Ark, 29 still have access to local camera data, and some appear to have made explicit searches on behalf of federal or out-of-state agencies. Elk Grove cited the Oregon State Police. Santa Clara police noted searches were for “DEA assist” 100 times. West Covina, Murrieta and Glendora police all indicated they searched for federal warrants. The Riverside County District Attorney’s Office wrote “ATF aid.”

The searches also include at least two by a Tiburon officer regarding a U.S. Postal Service investigation — which the town inadvertently included, unredacted, when it released the external audit logs.

“The Tiburon Police Department’s authorized users of the Flock system are fully compliant with SB 34,” the town posted on its website March 9. “Our officers have not, and will not, utilize the Flock system to share data in violation of state law.”

Internal department memos obtained by The Ark only partially explain why the audit missed so many agencies and apparently misidentified others. The memos show Tiburon audited for ICE, CBP and HSI — Immigration and Customs Enforcement, Customs and Border Protection and Homeland Security Investigations, ICE’s investigatory arm — along with USPS, USDA, DEA, U.S. Marshals Service, “U.S. Park Services,” Interpol and “federal.”

The memos indicate those keywords found 22 agencies, plus two more provided through The Ark’s earlier audit. One of those, Danville, had no entangled searches for July to December; Jean sent a letter, and the agency still has access.

However, using the search logs provided by the town, The Ark could not independently verify five of the agencies flagged by Tiburon, all of which received letters; one of those lost access and another, Mountain View, shut down its own Flock system in early February over privacy concerns.

Of the 22 agencies missed by the town audit, 18 conducted searches containing Tiburon’s audit terms but weren’t flagged. The remaining four had searches tied to the federal Bureau of Alcohol, Tobacco, Firearms and Explosives; the Department of Homeland Security; or JTTF, the FBI’s Joint Terrorism Task Force.

Jean did not address any questions about the discrepancies, limited audit terms or the department’s ability to audit its own system. As with The Ark’s initial investigation, Tiburon officials largely refused to comment or answer direct questions about the new findings, with no response at all from Mayor Jon Welner or Town Manager Greg Chanis. Jean’s March 9 email to The Ark partially answered just one of 13 questions, instead largely repeating the website announcement. She did not respond to a follow-up asking why she and other officials have refused to address the rest.

Shifting accountability

While Tiburon has been silent with the media, it has publicly claimed credit for changes to Flock’s system and cast them as progress.

“The town met with Flock’s legal counsel and project managers to limit how external agencies can search Tiburon’s (automated license-plate reader) data,” it said in the March 9 post. “Specifically, the town worked with Flock to allow external searches only for valid reasons, such as burglary, theft, homicide (i.e. criminal cases).”

Flock rolled out those limits to all California agencies about Dec. 16, not as a custom arrangement for Tiburon. The limits appear to be artificial.

Officers must now select a standardized crime category from a drop-down menu before running a search. The menu replaced the free-text-only field where officers described their purpose in their own words — “DEA assist,” CBP and “AOA HSI,” for “assist other agency,” all reasons agencies searched Tiburon’s cameras. The new categories are drawn from a federal crime-reporting framework: “Burglary/Breaking & Entering,” “Larceny/Theft Offenses,” “Traffic Infraction” and similar.

The free-text reason field still exists as an optional suffix. But with the preselected categories accepted as sufficient to trigger a search, many agencies have simply stopped filling it in, eliminating auditable phrases.

At the same time, Flock implemented a filter that blocks certain keywords — including terms related to immigration and reproductive health care — from being entered as search reasons. However, Flock, Tiburon and other agencies have mischaracterized this as blocking searches. Rather, the filter applies only to how searches are labeled, not to the data police officers can access. Nothing prevents the officer from adjusting a rejected reason and immediately trying the same search under a different category: A search conducted to assist a federal immigration task force or track a person who had an abortion is now recorded identically to a routine stolen-vehicle lookup or a death investigation, unless an officer voluntarily adds more detail.

As more departments stop using the free-text entry, the preapproved categories and blocked reasons increasingly produce cleaner logs that police and Flock can point to as proof of compliance — even if actual search behavior hasn’t changed.

“These drop-downs effectively give law enforcement options for how to avoid being transparent and honest about why they’re using the system,” said Nick Hidalgo, a senior staff attorney at the ACLU of Northern California. “If a law-enforcement officer is trying to help ICE and types in ‘ICE’ and receives an error, they can just pick whatever they want in order to get the information.”

He noted that police and Flock alike have been aware of California’s data-privacy and immigration-status laws for as long as they’ve been on the books.

“They are only implementing this change now to obscure things in their audit and search logs after a lot of transparency logs have been made public throughout the country showing these illegal purposes,” he said.

Efforts to reach Flock were unsuccessful.

Dave Maass, director of investigations at the Electronic Frontier Foundation, said the drop-down menu may have some analytical value, as roughly 10% of all searches simply said “investigation” and might now more closely align with an actual crime. But, he said, when officers were candidly entering “immigration” or “abortion” as search reasons because they didn’t expect the public to be reviewing the logs, the heightened media attention means that era is over regardless of a drop-down menu: “I don’t know that we could have the same faith that, now they know they’re being watched, they’re just going to continue to be honest about these more controversial uses.”

Hidalgo and Maass say filling in the free-text entry should already be mandatory under state law, as operators are required to collect the specific purpose of every search, not just a general crime category. The attorney general’s 2024 policy template calls for specific details, such as a case number, to tether each search to a documented, traceable investigation.

“I haven’t seen agencies really comply with that,” Hidalgo said.

Tiburon’s own officers have cited search reasons that don’t match department records. About 3 a.m. Feb. 11, a sergeant ran 12 consecutive searches of Feb. 3-10 camera records in roughly a half-hour span, citing “Motor Vehicle Theft/Stolen — Suspicious Vehicle,” according to an unredacted portion of the town’s February audit posted online. Monthly police stats, the department’s dispatch logs and LexisNexis’ Community Crime Map show no reported stolen vehicles in Tiburon or Belvedere during the search window — or in the prior 10 months.

San Jose, which is facing a lawsuit over its searches of license-plate data, has proposed requiring case numbers for each search. Tiburon and other Marin agencies have not indicated they plan to do so.

Flock has also stripped officer names and license-plate numbers from what the company calls Network Audit Logs — the records Tiburon uses to see how outside agencies have searched its data. Where an officer’s name once appeared, agencies now see an alphanumeric identifier. The license plate that was searched is gone entirely. If a host agency wants to know which officer conducted a specific search, Flock’s instructions say, it should contact the originating agency and “reference the unique alphanumeric search identifier.”

Even at Tiburon’s scale — 1.22 million searches from July to December, or more than 200,000 external searches per month — that suggestion is “practically impossible,” Maass said. Confirming the details of just 1% of searches would require roughly 2,000 reference calls to partner agencies each month. Tiburon now audits “at least five” external searches a month, according to the town’s new plate-data policy posted in December — roughly 0.0025% of activity.

But without the ability to retain a complete search record, Tiburon, Belvedere and other Flock clients may already be out of legal compliance by default. California law requires law-enforcement agencies to maintain a record of every search that includes, at minimum, the date and time, the license-plate number or other data queried, the username of the person who accessed the information and the organization they’re affiliated with.

“If Flock is not releasing the username of the person anymore to the agency, that agency is noncompliant with SB 34. Just right off the bat,” Maass said. “Removing from the network audits the name of the officer who ran the case and the plate — that’s just against the law. Period.”

Flock cited officer safety and investigation integrity as its reasons for withholding the data, but Hidalgo says the records privilege being invoked must be narrow: It applies only when there is “a concrete and definite prospect of criminal enforcement,” not as a blanket protection across millions of routine searches statewide.

The result, Hidalgo said, is not progress — it is erosion. “They’re just proving over and over again that they are incapable of complying with California privacy laws.”

A town apart

Tiburon’s response to increasing criticism of Flock and abuses of the company’s system has differed markedly from that of other agencies, including its two closest neighbors in Belvedere and Mill Valley.

In the March 9 post, Tiburon listed auditing and two self-attestation procedures as new protections of resident data. One is a simple disclaimer that agencies accessing Tiburon’s system will comply with state laws, which have been on the books for a decade and have not acted as a deterrent for dozens of California law-enforcement agencies to date. The other is revocation of access, where Tiburon will contact any agency it believes may have illegally searched the town’s plate data, as Jean did with her Jan. 15 letters.

On Feb. 18, four days after the deadline for agencies to explain their searches to Jean, The Ark requested copies of their responses. Tiburon had no records of responses from any of the 21 agencies contacted by letter and no records that the town referred any removed agencies to the attorney general.

“When civilians potentially violate state law, police investigate and refer to prosecutors,” Hidalgo said. “What we’ve seen here is one rule for law enforcement and another rule for everyone else.”

With no other reference records, The Ark instead reviewed Tiburon’s transparency portal on Flock’s website, which shows all current agencies with access to the town’s license-plate data. Tiburon removed four agencies before the Feb. 14 response deadline, including Beverly Hills, which in September conducted searches on 18,000 cameras across 613 agencies explicitly at the request of a DEA agent who phoned the department.

Then, in the three weeks following the deadline, Tiburon removed five more. That included the two biggest searchers of Tiburon’s system. The Riverside County Sheriff’s Office ran 10,707 searches citing the Department of Homeland Security, FBI, DEA, Marshals Service and Postal Service, plus a federal High Intensity Drug Trafficking Area program and the county’s Special Investigations Bureau, which has embedded federal agents. The Sheriff’s Office and other police departments in the area that participate in Riverside County’s investigations bureau ran thousands more searches not included in The Ark’s tally for subunits that collaborate with federal agents but that aren’t embedded on the teams. Orange County Sheriff’s Office made 4,771 searches citing Customs and Border Protection, Homeland Security Investigations and the federal drug-trafficking program. The two agencies — long identified by the ACLU, EFF and other media organizations as refusing to comply with SB 34 — together accounted for 96% of all potential violations.

The remaining agencies that Jean contacted have neither been removed nor provided explanations that Tiburon has disclosed under the California Public Records Act.

Even as the town revoked access for several agencies, Tiburon continued to grant new access faster than it was cutting it off — growing external shares by more than 50%, from 132 agencies in July to 199 as of March 23.

Still included are Concord and Seal Beach police, plus the Imperial County Sheriff’s Office, which all cited Homeland Security Investigations; Concord was flagged by Tiburon’s audit. The Riverside County District Attorney’s Office and Cathedral City police cited the Department of Homeland Security. Citrus Heights police cited the U.S. Postal Service 159 times, and the Santa Clara police cited the DEA and U.S. Marshals Service 103 times.

Tiburon, meanwhile, has also installed its first downtown cameras, placing two on a pole in front of the Belvedere-Tiburon Library along Tiburon Boulevard at Mar West Street. They were left over after the town found that eight Flock cameras could do the work at the previous locations requiring 12 Motorola cameras.

The Marin contrast

Belvedere and Mill Valley took a different approach after learning of their systems’ vulnerabilities.

On Feb. 12, just one day after The Ark printed its initial investigation into Tiburon’s Flock deployment, Belvedere severed access to all outside agencies except those located in Marin — the Mill Valley, Sausalito and Novato police departments, the Central Marin Police Authority, the Marin County Sheriff’s Office and the Marin District Attorney’s Office, according to Police Chief Jason Wu.

“Like many (California) agencies, once we were made aware that some (state) agencies had entangled searches with federal and out-of-state agencies, we took action to revoke access to our (automated license-plate reader) data,” said Wu, who voluntarily provided The Ark with October to December external searches and responded to all of the paper’s initial questions. “Our goal is to have our data available to all Marin County law-enforcement agencies with the Flock system upon implementation of our data-sharing agreement. It is our intent to only allow Marin County agencies to access our data at this time.”

The Ark’s review of Belvedere’s three months of data showed 15 agencies made 3,150 federally entangled searches, some the same as those made in Tiburon: Concord cited Homeland Security Investigations, Murrieta police cited a “DEA warrant,” Santa Clara police wrote “DEA assist” and West Covina police cited an “ATF search warrant.” In addition, the Northern California Regional Intelligence Center cited both “FBI investigation” and “Spokane DEA, drugs” — the latter an apparent search for a federal investigation on behalf of an out-of-state field office. All those agencies lost access when Belvedere limited its sharing in February.

Wu did not respond to a follow-up question about Belvedere’s timeline to develop and implement the new data-sharing agreement.

On Feb. 22, The Ark also requested November to December external-search logs from the Marin County Sheriff’s Office, which operates license-plate cameras in Strawberry. The county twice delayed release of the records and had not provided them by press time.

The Ark reviewed Mill Valley’s October to December records after Vice Mayor Caroline Joachim stated at a Feb. 2 City Council meeting that Mill Valley conducts “ongoing reviews and internal audits to confirm no unintended or improper access to our (automated license-plate reader) data” and that “there have been no known data breaches involving Mill Valley’s Flock systems.”

Eight agencies made 1,013 federally entangled searches in October before Mill Valley restricted access to six agencies in November, according to The Ark’s review, leaving no apparent violations in November or December. October searches included Los Angeles police searches citing U.S. Marshals Service and Interpol red notices — requests to provisionally arrest a person on behalf of foreign law-enforcement agencies.

When presented with the paper’s findings, Police Chief Rick Navarro reframed the issue as having been corrected, saying the city had been inadvertently enrolled in Flock’s Statewide Lookup Tool and had since deactivated it and restricted remaining access.

Despite the Los Angeles searches of the city’s system on behalf of a federal agency, Navarro asserted that “Mill Valley has yet to learn that any data within its (license-plate reader) system has been shared by a California law-enforcement agency or officer with a federal partner, and thus from our understanding there has been no ‘federal entanglements.’”

‘Full stop’

Auditing external search logs is complicated by the sheer volume of local and regional task forces with embedded federal agents, including immigration agents.

Tiburon did not disclose how many federally entangled search reasons it found, but its keywords indicate the town would have found about 500 records.

Tiburon did not audit for Riverside County’s Special Investigations Bureau or HIDTA, a regional, federally administered High Intensity Drug Trafficking Areas program under the DEA. Marin participates in the Northern California program, which includes nine federal agencies. Montclair police and the Orange County and Riverside County sheriff’s offices conducted 4,220 HIDTA searches in six months.

Flock’s filter does not block those terms as search reasons. But when The Ark included task forces with embedded federal agents and immigration agents in its audit, the results pushed past 16,000 hits — meaning the town found about three in 100 federally entangled searches.

The gap illustrates a structural problem: no local agency can identify every task force, subunit and embedded federal relationship across hundreds of partner agencies statewide, making comprehensive self-auditing effectively impossible.

Mill Valley’s Navarro offered the clearest articulation of the line law-enforcement agencies are attempting to draw: “California officers may continue to use (automated license-plate reader) data to safeguard their local communities without sharing that data with federal partners, even when working within those teams,” he told The Ark.

In practice, that distinction is difficult to maintain. Joint task forces are designed for information sharing; officers embedded in them operate under shared command structures and shared investigative goals. Under Hidalgo’s reading of SB 34, the illegal sharing occurs the moment a camera result factors into any investigation or prosecution involving federal agencies.

“Senate Bill 34 is pretty clear,” he said. “Any sharing with a federal agency or with a law-enforcement agency outside of the state is prohibited. And I think that applies regardless of whether a federal agent is based in California or whether they are embedded in a California state law-enforcement agency or a local law-enforcement agency. California law-enforcement agencies have to shut down any and all sharing of California driver location information with federal officers. Full stop.”

In the only question Jean responded to directly, she offered a defense of Tiburon’s own searches. The reason field in the sergeant’s two searches read “usps mail theft vehicle. San Mateo.”

“Just because a reason for search includes a ‘federal’ agency does not necessarily indicate specific data is being shared illegally,” Jean said. The searches, she said, were part of an active mail-theft investigation.

Her response left two questions unaddressed. The first: what happens when that investigation concludes — if Tiburon arrests a single suspect or uncovers an organized crime ring and turns camera data over to the U.S. Postal Inspection Service and federal prosecutors as part of an evidentiary file, does that constitute prohibited sharing? As with Navarro’s response, Jean appears to set aside what the department intends to do with the information and instead draws the line that no sharing has taken place — yet.

Town Attorney Ben Stock did not respond to a request for comment on the matter, while Wu and Navarro also didn’t respond to whether they’ve received legal advice through their cities or through the Marin County Police Chiefs Association. The California Attorney General’s Office also did not respond to requests for comment.

The second concerns a search with the specific citation of “San Mateo,” where the San Mateo Police Department does not have a sharing agreement with Tiburon. The same officer cited “MCPD AOA” — assist other agency — according to the department’s internal February audit, posted online. Searches conducted at the request of agencies that don’t have legal sharing agreements offer some of the clearest violations of SB 34, such as the Beverly Hills officer detailing the DEA search in plain language. If the Tiburon officer’s searches were conducted at the request of, or on behalf of, an officer in San Mateo or another department, were they in compliance with the town’s contractual data-sharing-agreement requirements?

“If you can’t follow your own policies about who to share the information with, and you can’t trust the vendor to keep the information limited to the people you claim to want to share it with,” Hidalgo said, “you’re just poking all these holes in the protections that are supposed to exist, and these systems become even less reliable than they already are.”

Under pressure nationwide

The questions facing Tiburon are playing out nationwide as Flock faces mounting scrutiny. Some 53 cities in 20 states have rejected or canceled contracts in the past year — up from roughly 30 at the time of The Ark’s February report. South Pasadena and Ithaca, New York, terminated their contracts citing privacy concerns. Lynnwood, Washington, canceled after finding more than 100,000 unauthorized searches. Denver ended its contract with Flock, specifically citing federal immigration agents’ use of the platform.

A class-action lawsuit filed Feb. 26 in San Francisco Superior Court names Flock as an automated license-plate reader “operator” with independent legal obligations under state privacy law. Among the plaintiffs is a San Rafael resident who passes 12 Flock cameras on his daily commute. The suit alleges Flock violated SB 34 by enabling and facilitating data sharing it was required to prevent.

“To protect public safety, you need public trust. As the Trump Administration continues to target California’s immigrant communities, it is important that state and local law enforcement are not seen as a tool in furthering the president’s mass-deportation agenda,” Attorney General Rob Bonta said in October. “When information about Californians leaves the state, we no longer have any say over how it is used or shared. That’s why the California Legislature passed SB 34 — to ensure information about Californians remains here in California.”

Not every city has chosen to cancel. San Jose’s City Council voted unanimously on March 11 to keep its 474-camera network in place but adopted new safeguards: cutting data retention from one year to 30 days, banning cameras near abortion clinics and places of worship and requiring officers to document specific case details — including a case number — for each search. Arlington Heights, Illinois, went further, renegotiating its Flock contract to include financial penalties for unauthorized data sharing, up to $70,000 per violation.

Richmond, which had disabled its cameras in December after a Flock configuration error allowed nationwide searches, voted 4-3 on March 18 to reactivate them as the city searches for a different vendor.

But Hidalgo said a different vendor is not the answer.

“All the (automated license-plate reader) vendors are going to have these same perverse incentives that make it really unlikely that they will be able to adequately comply with our laws and protect our privacy,” he said. Canceling Flock “is certainly protecting people in the short term,” but cities that cancel should “come to realize that actually what they should do is cancel the surveillance system in the long term.”

He noted the examples of abuse aren’t hypothetical. On Feb. 24, a Milwaukee officer was charged with misconduct after performing 179 Flock searches to track the person he was dating and their ex-partner. A Kansas police chief was charged in 2024 with using cameras to track his ex-girlfriend, and a Georgia police chief was charged in November with using cameras to stalk and harass private citizens. A Texas police department searched 83,000 records in three states to track a woman who had an abortion, logging evidence as a death investigation. And other departments have tracked participants in protests over the Trump administration, deportation raids and the Israel-Hamas war.

“If you were a perfect saint, you would still have a right to keep your information to yourself,” he said. “There’s no requirement that you be hiding something malicious in order to have a right to keep your damn life to yourself. Maybe you trust your local law enforcement. But do you trust law enforcement in the Central Valley? Or in Texas? Or in D.C.? If this information is collected, it can get into the hands of people who will misuse it.”

A warrant for that

While civil-liberties advocates say communities should have public conversations about whether they want cameras at all, they also seek alternatives to full shutdowns that Flock and police agencies are actively fighting.

Hidalgo argues that under the California Constitution, retrospective database searches — the kind that account for virtually every one of the searches identified in Tiburon’s data — should require a warrant, regardless of which agency is doing the searching or why.

The distinction is between two uses of the technology that look similar but are legally and practically different.

In a hot-list search, an officer flags a suspect’s plate; when any Flock camera in the network photographs it, the system sends an automatic alert. It produces a single data point — where a specific, already-identified vehicle is right now. Mill Valley’s Navarro described a recent example: when a stabbing occurred on Tower Drive, Marin sheriff’s deputies used Flock cameras to track and arrest the suspect within minutes. A child abduction, a fleeing murder suspect, a hit-and-run vehicle — the hot-list scenario is targeted, immediate and narrow.

“That kind of use I don’t think would require a warrant,” Hidalgo said.

Retrospective database searches work differently. An officer types in a plate number and retrieves every recorded sighting across the Flock network. Assembled over days, weeks or months, these images become a comprehensive record of private life constructed entirely from public data, which can locate a person’s home address, workplace, doctor’s office, children’s school, place of worship or the site of a protest they attended.

“What Flock cameras can do,” Hidalgo said, “is paint a shockingly and disturbingly accurate picture of our lives.”

The California Constitution’s right to privacy and its protection against unreasonable searches and seizures offer broader protections than the federal Fourth Amendment, Hidalgo said. That cameras photograph vehicles in public places does not, in his view, resolve the legal question. The constitutional question, Hidalgo argues, is not whether any single image is lawfully captured, but whether police may search a comprehensive archive of all of them — “first instinct, repeatedly, for every little thing” — without a warrant. A hearing in the San Jose case is scheduled for early August.

The warrant argument has drawn support across the political spectrum. The Institute for Justice, a libertarian public-interest law firm, is appealing a federal challenge to Flock cameras in Norfolk, Virginia, and has launched a nationwide campaign seeking warrant requirements in every state. Institute attorney Michael Soyfer has argued the constitutional standard should be “the degree of privacy from government that existed when the Fourth Amendment was ratified in 1791.”

“If one of the side effects of requiring a warrant was that law enforcement dramatically cut down on the number of searches they run,” Hidalgo said, “I think that’s actually just a good thing.”

Reach Executive Editor Kevin Hessel at 415-435-2652.