Virginia State police have recorded over 8 million images of license plates since 2010, in addition to images of every plate arriving from Virginia at the 2008 presidential inauguration, according to a Richmond Times-Dispatch report.
Police recorded the images at the inauguration, and at separate rallies several months earlier in Leesburg for Obama and Sarah Palin, at the request of the Secret Service. Automatic license plate readers have been in use for routine crime prevention purposes since 2006—but only in 2010 did state police begin storing images, for up to three years in some cases.
After Attorney General Ken Cuccinelli issued an opinion in February that the practice violated Virginia's Government Data Collection and Dissemination Practices Act, police destroyed the data.
Civil liberties groups like the ACLU have criticized the practice. In a recent report called "You Are Being Tracked," the group said that "license plate readers can be used for tracking people’s movements for months or years on end, chilling the exercise of our cherished rights to free speech and association."
The cameras are also in use in Fairfax County, where they help officers find stolen license plates, stolen vehicles and AMBER alerts. The devices may scan around 7,000 license plates on an average patrol shift. Patch reported in 2011 that Fairfax County Police purchased 26 of the cameras at a cost of $23,000 each, most with the help of a federal grant.