From: http://cironline.org

License-plate readers let police collect millions of records on drivers

The paperback-size device, installed on the outside of police cars, can log thousands of license plates in an eight-hour patrol shift. Katz-Lacabe said it had photographed his two cars on 112 occasions, including one image from 2009 that shows him and his daughters stepping out of his Toyota Prius in their driveway. …

In the Bay Area, at least 32 government agencies use license-plate readers. The city of Piedmont decided to install them along the border with Oakland, and the Marin County enclave of Tiburon placed plate scanners and cameras on two roads leading into and out of town. …

Katz-Lacabe, who was featured in a Wall Street Journal story last year, said he believes the records of his movements are too revealing for someone who has done nothing wrong. With the technology, he said, “you can tell who your friends are, who you hang out with, where you go to church, whether you’ve been to a political meeting.”

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