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Last week, the American Civil Liberties Union (ACLU) released its report on police use of automatic license-plate readers. Such systems read and track license plates, making a record of where and when a vehicle is photographed and  creating a useful law enforcement tool. But states have yet to work out a method for balancing law enforcement needs with individual privacy rights.

The ACLU report found that these scanners capture huge amounts of data, but that states are inconsistent in their use and retention of the information. The ACLU has proposed recommended guidelines for states to use as they craft regulations, and holds Minnesota up as an example that other states can follow.

License plate tracking debate simmers in Minnesota

 
Currently both the cities of St. Paul and Minneapolis store their data on plates not connected to crimes for 90 days before destroying it. The Minnesota State Patrol, which has only one vehicle equipped with ALPR cameras, destroys its data in 24 hours on plates not connected to an investigation. The Senate and House could not reach an agreement on how long that data should be stored. The Senate's version of the bill would've required police to purge it after 90 days, while the House version would've put that number at zero days. (KARE)

You can't hide from cops with license-plate scanners


Police say the devices are effective at finding stolen vehicles and cutting auto theft rates. Police also say they've used readers to solve cold cases, including homicides. The ACLU report says the plate scanning casts a wide net for little gain — that only "a tiny fraction of the license plate scans are flagged as 'hits.' For example, in Maryland, for every million plates read, only 47 (0.005%) were potentially associated with a stolen car or a person wanted for a crime." In one Sacramento shopping mall, private security officers snapped pictures of about 3 million plates in 27 months, identifying 51 stolen vehicles — but that's a success rate of just 0.0017%. (USA Today)

Watch an AP video on license-plate surveillance:

Police Documents on License Plate Scanners Reveal Mass Tracking


That is to say, the answer to regulating license plate readers is to have strict limits on how long plate data can be retained. While we don't recommend a specific cutoff date, we think it should be measured in days and weeks, not months and certainly not years. To their credit, some law enforcement agencies already comply with this principle. For example, the Minnesota State Patrol deletes all data after 48 hours. Others keep data for longer, and the rationale given is always the same: Although you can't tell immediately that someone is committing a crime, some of those people may well be doing something wrong, goes the argument. But in our society, the government doesn't watch all of us all the time just in case we commit a crime. (ACLU)

ACLU warns privacy at risk from license-plate readers

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