Two privacy activist groups formally appealed on Tuesday to the California Supreme Court, in their attempt to compel two Southern California law enforcement agencies to release one week’s worth of license plate reader data

In May 2013, the Electronic Frontier Foundation (EFF) and the American Civil Liberties Union of Southern California (ACLU SoCal) had sued the Los Angeles Police Department and the Los Angeles Sheriff’s Department to gain access to the data as a way to better understand this surveillance technology. The groups lost in 2014 at the lower court level and last month at the appellate court.

Both agencies, like many others nationwide, use license plate readers (LPRs, or ALPRs) to scan cars and compare them at incredible speeds to a "hot list" of stolen or wanted vehicles. In some cases, that data is kept for weeks, months, or even years. Handing over such a large volume of records by a California law enforcement agency is not without precedent.

Earlier this year, Ars obtained 4.6 million LPR records collected by the police in Oakland over four years and learned that just 0.16 percent of those reads were "hits." We discovered that such data is incredibly revelatory—we were even able to find the city block where a member of the city council lives, using nothing but the database, a related data visualization tool, and his license plate number.

The judge in the initial court ruling found that the law enforcement agencies could withhold LPR records—which include a plate number, date, time, and GPS location—through a particular exemption under the California Public Records Act that allows investigatory records to be kept private.

The EFF and the ACLU SoCal argue that interpreting the investigations provisions so broadly creates a ridiculous result.

By interpreting § 6254(f) to shield from public view this entire class of records, the Court of Appeal improperly expanded the scope of that exemption beyond prior precedent as established by this Court in Williams v. Superior Court, 5 Cal. 4th 337 (1993) and Haynie v. Superior Court, 26 Cal. 4th 1061 (2001), and so stretched the meaning of “investigation” as to force the absurd result that all cars in Los Angeles are constantly under police investigation. … The court also failed to address the fundamental differences between the mass surveillance technology in ALPRs and traditional human policing, and instead mechanically applied old caselaw addressing targeted investigations by human officers to ALPR technology. Indeed, the court’s opinion rests on the presumption that there is no difference between an officer manually checking a single license plate and high-tech surveillance equipment automatically cataloging the locations of millions of vehicles in Los Angeles every week.

What's an investigation, anyway?

Previously, as Ars has reported, I have run into similar walls when trying to access my own license plate reader data from various cities. Various agencies that we queried, including the LAPD and LASD, the San Mateo County Sheriff’s Office, and the Piedmont Police Department have all denied such records under § 6254(f) of the California Public Records Act, and a related provision, subsection (k).

In 2013, we outlined some previous California judicial findings as to why we didn’t think the government’s claim holds water. That included (Haynie v. Superior Court) from 2001, a California appellate court again found that law enforcement agencies could not summarily restrict access. Yet, by including "routine" and "everyday" within the ambit of "investigations" in section 6254(f), we do not mean to shield everything law enforcement officers do from disclosure. (Cf. ACLU, supra, 32 Cal.3d at p. 449.) Often, officers make inquiries of citizens for purposes related to crime prevention and public safety that are unrelated to either civil or criminal investigations. The records of investigation exempted under section 6254(f) encompass only those investigations undertaken for the purpose of determining whether a violation of law may occur or has occurred.

The ACLU and EFF cite this case extensively in their Supreme Court petition:

In Haynie, this Court stated, “we do not mean to shield everything law enforcement officers do from disclosure.” 26 Cal. 4th at 1071. In doing so, the Court acknowledged the “records of . . . investigations” exemption has limiting principles, even if it did not define at the time what those were. The automated collection of data on millions of innocent drivers in Los Angeles is not an “investigation” within the meaning of Haynie or any of the cases to apply its rule. ALPRs do not involve a “decision” to investigate like the “decision to stop Haynie,” Haynie, 26 Cal. 4th at 1071; they also do not involve any specific allegations of wrongdoing or a connection to any particular crime. Instead, LPR cameras automatically photograph all plates within view without the driver’s knowledge, without the officer targeting any particular car, and without any level of suspicion. Under no prior cases is such data-gathering an “investigation” for purposes of § 6254(f).

The court’s review is not automatic: the California Supreme Court only agrees to hear a small fraction of the cases that are submitted to it.