A Flock camera photographs each vehicle that passes it, whether or not the driver is suspected of anything. It logs the plate, time, and location. Flock's Vehicle Fingerprint feature also records the make, model, and color, plus details like dents and bumper stickers, so a car can be found even without a readable plate.

Those records go into Flock's cloud, where police departments can search them and share them with other agencies across city and state lines. Flock says its network processes more than 20 billion vehicle reads a month across 49 states.

That kind of broad access leaves much room for misuse and abuse. A Washington Post review found at least 50 officers accused or charged with misusing license plate readers, often to follow people in their personal lives; Flock's system was involved in 46 of those cases. We asked Flock's CEO, Garrett Langley, how the company responds to misuse and who controls the data its devices collect.