The City of Paradise Valley, Arizona (population: 12,820) is so concerned with keeping its newly deployed license plate reader (LPR) system a secret that it has installed dozens of fake cactuses with the cameras mounted inside.

The wealthy Phoenix suburb has been reticent to explain why the cameras are necessary. Fox 10 News, a local television station, reported earlier this week that the Paradise Valley Police declined to comment on the installation of the devices.

Kevin Burke, the town manager, provided Fox 10 with a confusing answer, saying that the LPRs were not active. This claim comes despite the fact that last Saturday, the Paradise Valley Police announced it had recorded its first LPR hit, which resulted in a traffic stop but no arrest.

"We want to make sure we're answering everybody's questions about data retention [and] how the things will be used. We want to make sure that is vetted before we turn these things up," he said, adding that the fake cactus setup is designed to be "aesthetically pleasing" rather than sneaky.

Neither Burke nor police spokesman Lt. Michael Horn responded to Ars’ request for comment.

The Paradise Valley Police, like many other departments nationwide, use these specialized cameras 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.

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.

Hide and seek

"It seems comical, but given the photo, not exactly an effort at concealment," Catherine Crump, a law professor at the University of California, Berkeley, told Ars. "I am more interested in what else this town is doing with its $2 million police technology upgrade."

Covert LPRs are not new. A 2010 presentation by George Mason University researchers showed LPRs being hidden in ladders and even taxis. Kade Crockford, an activist with the American Civil Liberties Union of Massachusetts, told Ars that other law enforcement agencies have even mounted such cameras on unmarked police vehicles.

Mike Katz-Lacabe, a privacy activist based in San Leandro, California, told Ars that this supposed attempt at secrecy isn't particularly effective.

"By hiding them in this manner, the town appears to know that what they are doing is either wrong or will be perceived as negative," he told Ars. "If the cameras are a useful and legitimate tool, why are they attempting to hide them? However, what law enforcement and the town will claim is that hiding the cameras is necessary so that the 'bad guys' don’t know where they are and then avoid driving past them."

Thanks to Ars reader Dave Piasecki for pointing this story out to us.