For months now, we’ve been following the rapid expansion of license plate readers across America. The growth is fueled by federal law enforcement grants that allow for such data to be instantly shared with federal authorities.

We’ve published stories showing how people crossing the US-Mexico border are routinely subject to license plate scans, which is in turn, shared with insurance companies. An intrepid data scientist claimed to have found the location of Minneapolis’ stationary LPRs based on studying public records of the complete log file that he had requested. (Months later, the state law allowing for such access was changed.) As recently as March 2013, Piedmont, a rich Northern California town that is surrounded by Oakland, moved toward placing such devices at its entire city border with Oakland.

On Monday, two Californian civil liberties groups filed a lawsuit against the Los Angeles Police Department (LAPD) and the Los Angeles Sheriff’s Department (LASD) in an attempt to compel these agencies to release a week’s worth of automated license plate reader (ALPR, or sometimes, LPR) data from August 2012. The non-profits claim that these agencies are required to do so under the California Public Records Act. In late July 2012, the American Civil Liberties Union and its affiliates sent requests to local police departments and state agencies across 38 states to request information on how LPRs are used.

The American Civil Liberties Union Foundation of Southern California (ACLU) and the Electronic Frontier Foundation (EFF) sought “all ALPR data collected or generated between 12:01 AM on August 12, 2012 and 11:59 PM on August 19, 2012, including at a minimum, the license plate number, date, time, and location information for each license plate recorded.” In its complaint, the ACLU and the EFF allege that the LASD has “not provided Petitioner with any records.”

A spokesperson for the LAPD declined to comment to Ars on the case.

“We disagree with the complaint which is why we're more than willing to take argument in front of a judge and let the judge decide. This is where the rule of law will play a major role in this,” Steve Whitmore, an LASD spokesperson, told Ars. “Some of [these plates] are part of investigations, they are confidential. We're not going to give out that information, it's a violation of their privacy.”

Specifically, he cited, as do the LASD’s previous written responses, California’s Evidence 1040(b)(2): “Disclosure of the information is against the public interest because there is a necessity for preserving the confidentiality of the information that outweighs the necessity for disclosure in the interest of justice.”

However, Whitmore did not know whether an individual could request her or his own license plate reader data and associated photographs, nor if any individuals had done so previously

“You have every right to do that and I encourage you to do that,” he told Ars.

Seven days

Jennifer Lynch, one of the EFF attorneys that filed the lawsuit, told Ars that this particular week was selected for a number of reasons.

“I wanted to get the data for one week because I wanted to limit it so we could do something with it and weren't overwhelmed,” she said. “With a week's worth of data you can see where the cops are focusing their efforts. You would be able to see whether the same plate is scanned multiple times during the same week. [The LASD and LAPD] probably have the largest volume of this type of data and they're representative of large scale cities around the country.”

She added in that year, it was also the last week of the Muslim holy week of Ramadan.

“The fact that there has been quite a bit of government surveillance of Muslim communities in Los Angeles, and I thought getting license plate data from the last week of Ramadan might be able to tell us if the cops were focusing their surveillance efforts on Muslim communities and businesses during that week,” she clarified by e-mail.

Lynch added that she had no idea how many records might turn up on an average week, but suspected that it might be in the hundreds of thousands.

“The information that we have for LASD is that they're able to record more than 14,000 plates during a shift,” she said. “We would need to know how many cars are equipped with these cameras and how frequently they're driving around.”