from ACLU.org: Automatic license plate readers are the most widespread location
tracking technology you’ve probably never heard of. Mounted on patrol
cars or stationary objects like bridges, they snap photos of every
passing car, recording their plate numbers, times, and locations.
first the captured plate data was used just to check against lists of
cars law enforcement hoped to locate for various reasons (to act on
arrest warrants, find stolen cars, etc.). But increasingly, all of this
data is being fed into massive databases that contain the location
information of many millions of innocent Americans stretching back for
months or even years.
This is what we have found after analyzing more than 26,000 pages of
documents from police departments in cities and towns across the
country, obtained through freedom of information requests by ACLU
affiliates in 38 states and Washington, D.C. As it becomes increasingly
clear that ours is an era of mass surveillance facilitated by ever
cheaper and more powerful computing technology (think about the NSA's
call logging program), it is critical we learn how this technology is
License plate readers are just one example of a disturbing
phenomenon: the government is increasingly using new technology to
collect information about all of us, all the time, and to store it
forever – providing a complete record of our lives for it to access at
As is often the case with surveillance technology, there are
unobjectionable – even beneficial – uses of license plate readers. We
don’t object when they’re used to identify people who are driving stolen
cars or are subject to an arrest warrant. But they should not become
tools for tracking where each of us has driven.
License plate readers capture vast amounts of data on innocent people
Because of the way the technology works – these devices snap photos
of every passing car, not just those registered to people suspected of
crimes – virtually all of the data license plate readers gather is about
people who are completely innocent. Data that we obtained through our
records requests illustrates this point vividly:
Why we should worry
Should the government be logging for months, years, or indefinitely
the movements of the other 99 percent of people, who are innocent?
The answer to this question is no. License plate reader information
can be very revealing. While one snapshot at one point might not seem
sensitive, as blankets of plate readers cover our streets, and as the
government stores data for longer and longer, the technology quickly
morphs into a powerful tracking tool.
As computer technology and storage capacity get cheaper every year,
we need to prepare for a future not just where there are a few license
plate reader cameras in every town, but one in which there are multiple
cameras on every block.
What can location data reveal about people? Trips to places of
worship, political protests, or gun ranges can be powerful indicators of
people’s beliefs. Is it really the government’s business how often you
go to the drug store or liquor store, what doctors you visit, and the
identities of your friends? I’m sure all of us can remember something
from our past that could embarrass us. If the government comes to
suspect you of something in 2020, should it have access to databases
stretching back years that could dig up facts about you that previously
What's happening now
Law enforcement data-retention policies today are all over the map.
While some police departments store data briefly, others keep it for a
long time, or indefinitely.
The government doesn’t have a great track record of using this kind
of information responsibly. As our report details, the data can be
abused for official purposes, like spying on protesters merely because
they are exercising their constitutionally protected right to petition
the government, or unofficial ones, like tracking an ex-spouse.
Prior to the rise of powerful surveillance technology, it simply
wasn’t possible to watch all of the people all of the time. But as these
natural limits erode and the impossible becomes possible, we have to
make conscious choices about how technology should be used.
What's the right line with license plate readers?
There is a reasonable way to regulate this technology. The primary
law enforcement use of these systems is to take pictures of plates to
make it possible to check them against “hot lists” of cars of interest
to law enforcement. This can be done virtually instantaneously. While
plates that generate a “hit” may need to be stored for investigative
purposes, there is no need to store plates for months or years to achieve this purpose.
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.
This is not just an issue we’ll have to decide in the context of
license plate readers, but the most important surveillance issue of our
time. Should the NSA collect all data about everyone’s calls, just in case
it’s useful to identify a terrorist? Why stop there? Why not store all
of the contents of the calls we make as well? And emails? This is not
just about communications or public movements. It’s also about what
happens inside the home.
As electric companies convert to “smart grids” that provide them data
about the patterns of your electricity usage, it could well become
apparent when you take a shower and whether you run your dishwasher more
frequently than others in your demographic profile.
License plate readers are just one manifestation of trend. Is this a test case that we can get right?
There is a lot more in the report than I’ve covered in this blog
post. Give it a read – I hope you find it thought-provoking. We’ll be
posting more blog posts in coming days on different aspects of what
we’ve learned about license plate readers. We also invite you to go
through the documents yourself.
There is more in there than we with our
small staff could fully examine, so further newsworthy discoveries may
still lurk within, waiting to be discovered. And join us on twitter
(hashtag #autotracking) to discuss your finds.