Police Documents on License Plate Scanners Reveal Mass Tracking

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. At 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 being used. 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 will.

Today, we are releasing all of the documents we have received (accessible through this interactive map and this issue page) and are publishing a report, “You Are Being Tracked,” which explains what these documents say about license plate readers: what they are capable of, how they are being used, and what privacy harms they can cause if protections aren’t put in place. We’re also offering more than a dozen recommendations we think local police departments and state legislatures should follow when they pass laws about this technology.

Check out this great explainer about the technology:

Privacy statement. This embed will serve content from newsbound.com.

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 went unnoticed?

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.

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Face it people.The days of old are gone.So are most all of your rights.The constitution means what they say it means.Local police make their own laws as they go...blah blah blah.The problem is......it is too late to do anything about it.Welcome to the beginnings of the new world order.There is NOTHING you can do.Accept it,live with it.Harsh words for sure....but true.


The repossession industry has embraced this technology as well.


They push and push until everyone just gives their rights up. It seems to already be working.. Note the comment:

"There is no reason to have this sort of pervasive surveillance of i nnocent people and I see it as a violation of the Fourth Amendment.

But, what else is new... "

The last line of this comment is exactly proof that the gov't is succeeding in influencing the general population of the US into thinking this is okay to do. The line I'm referring to is the 'But, what else is new'. This needs to stop, and cuts need to be done since our tax money is going to the government so in-turn they can track us.


I feel that I've been included in the license plate tracking.June of 1998,Ihad taken a student home at the quest of his mother.they lived in the projects.On my way back to work,in my rush Idrove on a street going thr wrong way for half a block.When I realized what I had done I corrected my mistake.Seconds later I saw the police following me back to work.Never did the stop me! They have been coming to my home undercover claim the're selling products,home improvements,asking surveying questions and in a meat truck several times.When driving in other counties,they also follow me.What can be done about this?


I can't believe it's taken the ACLU this long to jump on this topic. I went to visit Mount Rushmore two summers ago and had my plate scanned as I entered the parking area. At the toll booth, after paying, I was given back a receipt with all my personnnel information printed on it. I asked the booth attendent how he got this info and he responed "by a licence plate scanner". The parking lot is run by a private contractor so it's not just the government scanning plates. By the way, the attendent told me my plate had been scanned four times that day already. What an amazing technology!


This is much ado about nothing. These scanners read thousands of plates per day. Most departments mount them on the cruisers of their top traffic officers. As the article stated they flag certain offender plates (amber alerts/warrants/suspensions). The flagged plates cause the computer to beep. The officer clicks the icon to see the information regarding that plate. The flagged plate is actually the only ones that officer's computer shows. The record of all plates scanned may be somewhere in the cruiser's computer, but police departments do not have the NSA's budget. No one is looking at this information. It does not go to a central database. They are not being intexed. To the comment about driving being a right, courts have held that driving is a privilege not a right.


Plates, and drivers licenses too, are nothing more than badges of our slavery. The day will come when we dispense with the damn things.

By the way, the "plate data retention period" is always indefinite, no matter what the statute says. It's naive to think otherwise, as there is never any penalty for violating such statutes. The laws are for the peons, not the ruling class.


I appreciate all the hand-wringing and concern, and I certainly agree that this is a cause for concern - not something our founding fathers anticipated.

At the same time, I worked for NSA with a very high security clearance myself for several years. I saw things done that were legally questionable even under older laws. I contemplated this very issue -- inside a highly classified facility -- before most of the readers of this site were even born, and before high technology things like digital wristwatches and hand calculators.

While I applaud the noble effort for freedom, you ain't gonna stop it. No way in hell. The formula is (massive government budget) + (some real justification for some of it) + (universal knowledge of just about everything through computers) + (no way in hell you will ever get in to a classified facility to see what is going on before they hit the Delete button, anyway).

Besides, Wal-Mart and other big companies are already tracking you like lab rats, anyway, so what are you worried about? Anyone who wants to can track all your movements right now, on a budget that even an ordinary citizen can afford.

Privacy is a myth in the age of high tech. The only reason you have any privacy at all is because your life is simply too boring for anybody to bother to watch you.


First it was the cameras on the traffic signals, then it was the drones, the NSA and the license plate readers. This surveillance sure feels like a precursor to complete government control. But what do I know? I keep hearing the echo of some author droning on and on about something that happened in 1984. And then they came for me.


The guy that says they aren't doing anything with the information is DEAD wrong. Better clean out your ears. I can tell you CHP is tracking you and all your movements. Please say how crazy I am. What I do know is this! We have two homes, one in CA and one in AZ. One of our vehicles is lic in Az. We go back and forth. I got a letter in the mail that my Az lic plate had " too many hits." Im required to have a CA drivers lic due to my job. My wife has Az lic, insurance ,etc. I was told I'm not allowed to drive that vehicle when it's in CA. Also they require I register anything I own to CA because I'm employed in the state. More to the story but that is a very shortened version. Guess what? 1984 is here...


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