The Boston Police Department has suspended their use of license plate scanners for now. It seems the optical character recognition technology was working just fine, but the department wasn't following up on all of the hot crime fighting leads the technology was generating. The scanners collected about four million plate IDs a year, prompting onlookers to ask whether the inherent privacy issues were outweighed by the law enforcement benefits.
License plate scanners (LPS) have been in place for years in thousands of cities. They can identify the location of the plate, "read" the characters on the plate and cross-reference them with a database of vehicles of interest. Stolen vehicles, vehicles belonging to wanted individuals, and others can theoretically be located this way. In order for the system to work, all plates must be scanned but not necessarily stored.
In Boston, the only reason the department halted its use of LPS was because the Boston Globe and MuckRock were accidentally given a complete and non-redacted report of the LPS data findings. It turned out that many vehicle locations and plate numbers were logged with the time and date -- regardless of whether the vehicles were wanted. The information was stored in databanks without an expiration date. Even many of the department's own cars parked in the depot were in the databank.
On the other side of the equation, it seems LPS findings weren't always being followed up by police action. For example, a particular stolen motorcycle was seen 59 times over 5 months without a peep from the BPD. We don't know what percentage of followups there were, but it certainly wasn't 100%. This begs the question: Are police departments around the world using LPS to fight crime, or is this just one giant tracking system for every vehicle on the road?