The ACLU reports today that routine tracking and storage of license plate information is becoming increasingly common:
License plate readers would pose few civil liberties risks if they only checked plates against hot lists and these hot lists were implemented soundly. But these systems are conﬁgured to store the photograph, the license plate number, and the date, time, and location where all vehicles are seen — not just the data of vehicles that generate hits. All of this information is being placed into databases, and is sometimes pooled into regional sharing systems.
....More and more cameras, longer retention periods, and widespread sharing allow law enforcement agents to assemble the individual puzzle pieces of where we have been over time into a single, high-resolution image of our lives. The knowledge that one is subject to constant monitoring can chill the exercise of our cherished rights to free speech and association. Databases of license plate reader information create opportunities for institutional abuse, such as using them to identify protest attendees merely because these individuals have exercised their First Amendment-protected right to free speech. If not properly secured, license plate reader databases open the door to abusive tracking, enabling anyone with access to pry into the lives of his boss, his ex-wife, or his romantic, political, or workplace rivals.
The chart on the right is for Maryland: for every million license plates read, only 47 were even tentatively associated with actual serious crimes.
As with NSA phone records, this is something we have to figure out as a society. These kinds of databases almost certainly help to catch bad guys. Nobody knows how much they help, but it's probably nonzero. So is that worth it? Do we mind having government agencies track our public movements every minute of the day? Do we mind if they team up with the private sector to track our buying habits? Do we mind if they keep track of who we call, who we email, and who we send letters to? Do we seriously think that if we shrug our shoulders at this, that it won't someday be abused on a massive scale?
I don't. But I'm unsure of how my fellow citizens feel about this. Most of them don't really seem to mind as long as they think it keeps them just a little bit safer.