The shocking police crackdown on protestors in Ferguson, Missouri, in the wake of the police  shooting of Michael Brown, underscored the extent to which advanced military weapons and equipment, designed for the battlefield, are making their way to small-town police departments across the United States. Although much tougher to observe, this same thing is happening  with surveillance equipment. NSA-style mass  surveillance is enabling local police departments  to gather vast quantities of sensitive information about each and every one of us in a way that was never previously possible. Location information can  be very sensitive. If you drive your car around the United States, it can reveal if you go  to a therapist, attend an Alcoholics Anonymous meeting, if you go to church  or if you don't go to church. And when that  information about you is combined with the same information about everyone else, the government can gain  a detailed portrait of how private citizens interact. This information used to be private. Thanks to modern technology, the government knows far too much about what happens behind closed doors. And local police departments make decisions about who they think you are based on this information. One of the key technologies  driving mass location tracking is the innocuous-sounding Automatic License Plate Reader. If you haven't seen one, it's probably because you didn't know what to look for -- they're everywhere. Mounted on roads or  on police cars, Automatic License Plate Readers capture images of every passing car and convert the license plate into machine-readable text so that they can be checked against hot lists of cars potentially wanted for wrongdoing. But more than that, increasingly, local police departments  are keeping records not just of people wanted for wrongdoing, but of every plate that  passes them by, resulting in the collection of mass quantities of data about where Americans have gone. Did you know this was happening? When Mike Katz-Lacabe asked his local police department for information about the plate reader data they had on him, this is what they got: in addition to the date,  time and location, the police department had  photographs that captured where he was going and  often who he was with. The second photo from the top is a picture of Mike and his two daughters getting out of their car in their own driveway. The government has  hundreds of photos like this about Mike going about his daily life. And if you drive a car  in the United States, I would bet money  that they have photographs like this of you going about your daily life. Mike hasn't done anything wrong. Why is it okay that the government is keeping all of this information? The reason it's happening is because, as the cost of storing this data has plummeted, the police departments simply hang on to it, just in case it could be useful someday. The issue is not just that one police department is gathering this information in isolation or even that multiple police  departments are doing it. At the same time, the federal government is collecting all of these individual pots of data, and pooling them together  into one vast database with hundreds of millions of hits, showing where Americans have traveled. This document from the  Federal Drug Enforcement Administration, which is one of the agencies primarily interested in this, is one of several that reveal  the existence of this database. Meanwhile, in New York City, the NYPD has driven police cars equipped with license plate readers past mosques in order to figure out who is attending. The uses and abuses of this technology aren't limited to the United States. In the U.K., the police department put 80-year-old John Kat on a plate reader watch list after he had attended dozens of lawful political demonstrations where he liked to sit on a bench and sketch the attendees. License plate readers aren't the only mass location tracking technology available to law enforcement agents today. Through a technique known as a cell tower dump, law enforcement agents can uncover who was using one or more cell towers at a particular time, a technique which has been known to reveal the location of tens of thousands and even hundreds of thousands of people. Also, using a device known as a StingRay, law enforcement agents can send tracking signals inside people's houses to identify the cell phones located there. And if they don't know which house to target, they've been known  to drive this technology around through whole neighborhoods. Just as the police in Ferguson possess high-tech military weapons and equipment, so too do police departments across the United States possess high-tech surveillance gear. Just because you don't see it, doesn't mean it's not there. The question is, what should we do about this? I think this poses a serious civil liberties threat. History has shown that once the police  have massive quantities of data, tracking the movements of innocent people, it gets abused, maybe for blackmail, maybe for political advantage, or maybe for simple voyeurism. Fortunately, there are steps we can take. Local police departments can  be governed by the city councils, which can pass laws requiring the police to dispose of the data  about innocent people while allowing the legitimate uses of the technology to go forward. Thank you. (Applause).