OAKLAND, CA—The last time the Oakland Police Department (OPD) saw me was on May 6, 2013 at 6:38:25pm.

My car was at the corner of Mandana Blvd. and Grand Ave., just blocks away from the apartment that my wife and I moved out of about a month earlier. It’s an intersection I drive through fairly frequently even now, and the OPD’s own license plate reader (LPR) data bears that out. One of its LPRs—Unit 1825—captured my car passing through that intersection twice between late April 2013 and early May 2013.

I have no criminal record, have committed no crime, and am not (as far as I know) under investigation by the OPD or any law enforcement agency. Since I first moved to Oakland in 2005, I’ve been pulled over by the OPD exactly once—for accidentally not making a complete stop while making a right-hand turn at a red light—four years ago. Nevertheless, the OPD’s LPR system captured my car 13 times between April 29, 2012 and May 6, 2013 at various points around the city, and it retained that data. My car is neither wanted nor stolen. The OPD has no warrant on me, no probable cause, and no reasonable suspicion of wrongdoing, yet it watches where I go. Is that a problem?

LPR deployments—which are rapidly expanding throughout the country to cities and towns big and small—help law enforcement officers scan license plates extremely quickly (typically, 60 plates per second) and run those against a “hot list” of cars that are wanted or stolen. The cameras themselves can be hidden inside infrastructure or mounted onto squad cars. Law enforcement agencies love them. The federal government is even encouraging local law enforcement (through federal grants) to purchase more for several thousand dollars apiece. But LPRs aren't just looking for stolen cars; they capture every plate that they see. In some cases, they retain that plate, location, date, and time information... indefinitely.

Sid Heal is a recently retired commander who evaluated technology during his decades-long tenure at the Los Angeles County Sheriff's Department. He's now a law enforcement consultant and told Ars last year that he's been working with LPRs since 2005.

"It was one of the few technologies that did everything that they said it did as well as they said it did," he said. "It staggered the imagination."

Why does OPD hold records of my car that are more than a year old? Was that data ever accessed by or shared with the Northern California Regional Intelligence Center (NCRIC), a federally funded "fusion center" based in San Francisco? What about other federal agencies? Since asking on July 1, 2013, the OPD has yet to respond to my follow-up questions.

In May 2013, we wrote about a lawsuit filed by the American Civil Liberties Union (ACLU) and the Electronic Frontier Foundation (EFF) against the Los Angeles Police Department (LAPD) and the Los Angeles County Sheriff’s Department (LASD), two of the largest local law enforcement agencies in the country. The plaintiffs asked for “all ALPR data collected or generated between 12:01am on August 12, 2012 and 11:59pm on August 19, 2012, including at a minimum, the license plate number, date, time, and location information for each license plate recorded.”

That case is still pending, but it sparked this idea: why not find out what data exists on my own car? Under the California Public Records Act, I should be able to gain access to my own data—but it turns out that getting information from regional law enforcement agencies is an exercise in both patience and frustration. I’ve spent the last two months trying to track down precisely what LPR data various law enforcement agencies around the San Francisco Bay Area (and a few in Southern California) have captured on my vehicle over the last year. This is uncommon; even here in the Bay Area with its privacy-conscious and tech-savvy users, few people appear to know just how much data the police hold on them. In many cases, I was one of just a few people (and sometimes the only person) to request such data about myself. This is what I found.

See no evil

On May 8, 2013, I submitted a signed letter to the OPD asking for “all data recorded by your agency’s automated license plate reader (ALPR) system between May 6, 2012 and May 6, 2013 for my vehicle, [REDACTED]. This data should include, at a minimum, the license plate number, date, time, and location information.”

I submitted similar letters to the neighboring Berkeley Police Department (BPD), the San Francisco Police Department (SFPD), the remaining eight Bay Area county sheriff’s departments, and NCRIC itself. I also made similar requests to the LAPD, LASD, and to my hometown force, the Santa Monica Police Department (SMPD).

Of the 14 agencies I queried, OPD—to its credit—came back with the most substantial dataset. After nearly two months of waiting, it provided a list of 13 data points, many clustered right at an apartment near the Berkeley/Oakland border that my wife and I rented for six weeks in Spring 2012.

View Cyrus Farivar's LPR data (May 2012-May 2013) in a larger map

I included the other Southern California entities because my father and brother still live in Santa Monica, and I travel down there a few times per year. The SMPD, with its 11 LPRs, apparently only read my plate once near a freeway onramp that I’ve taken to get to and from my father’s home. (In order to get it, I had to send the SMPD proof of my own car registration—this was the only agency to ask for such documentation.)

The others? Some apparently never saw me at all.

The San Francisco Police Department, with its 24 LPRs, told me by e-mail that my car “was not recorded on our agency’s ALPR system.”

Closer to home, the Alameda County Sheriff’s Office—the county that encompasses Oakland, Berkeley, and a number of other East Bay communities—also said that armed with its seven LPR devices: “we do not have any record of your vehicle.” Our county neighbor to the north, Contra Costa County, apparently didn’t record me either.

Interestingly, some said that they didn’t have any LPR system at all. Santa Clara County (home of Google, Apple, and Yahoo, among other tech giants) told me that its sheriff’s department does not have an LPR system. Neither does Sonoma County, north of the Bay Area.

“This is in response to your request for ALPR data from our agency,” wrote the Napa County Sheriff, home to one of California’s best-known wine regions. “Our agency does not use ALPR readers, therefore we have no data to provide you.”

Solano County, adjacent to Napa County, cryptically told me: “No responsive Sheriff's Office records exist because no information is stored.”