Last week, we filmed our second episode of Ars Technica Live in Oakland, California, and we had a tremendously interesting conversation with UC Davis law professor Elizabeth Joh, who researches surveillance technology and policing. Right out of the gate, Joh made it clear that the problem isn't surveillance per se—governments "need surveillance," she said, to figure out what its citizens require in terms of benefits, help, and security. The problem is when this surveillance becomes invasive, and the government inhibits freedom of expression and punishes unconventional behavior. How do we balance the need for surveillance and the need for free expression and privacy in a democratic society?

Joh talked a lot about the future legal landscape we're creating with cutting-edge technologies like self-driving cars, facial recognition, and body cams. When you're talking about law and policy, the issue is always that adoption of devices like body cams tends to precede careful thought about what rules will govern them. After the Ferguson protests, for example, police departments started using body cams as an accountability measure. But there are no federal guidelines for how cops will use these cams. Will they be able to turn them off whenever they want? Who has access to the data they collect? Can they use facial recognition in body cams? All of these questions remain unanswered, yet body cams are in widespread use across the US.

A similar problem dogs our use of DNA databases, Joh explained. The US government gives states financial incentives to develop databases and biological sample libraries with the DNA of everyone who gets arrested. These aren't convicts, mind you—just anyone who gets arrested, regardless of whether they were released the next day or found guilty of a felony. Again, the question here is how to regulate these databases, as well as other digital databases full of our "information microbiome." The key, Joh argued, isn't going to be found in the courts or Congress. Instead, "public vigilance" is the only social force that moves fast enough to push government to behave responsibly with new surveillance technologies.

Of course, public vigilance is only as good as public information, and if the public doesn't know what data law enforcement has, we can't push for better rules. That's why the rise of private security forces is so troubling. Joh estimated that private security forces, from guards at 7-11 to "Target's private crime lab," are 3-5 times larger than public forces. And they are not regulated by government in any way, which means that it's impossible for the public to know what kinds of data private forces are gathering.

In the question and answer period, Joh talked about the future of surveillance tech in the US. Though self-driving cars may be great for safety, they will also log everywhere you go. Who will have access to all the information generated by these cars? She also believes very strongly that robots will become a key part of law enforcement, whether via surveillance drones or actual Robocop-style police officers who arrest people. She's also very concerned about "predictive policing," or using algorithms to predict where crimes will happen and who is likely to be involved in them. The idea of "pre crime police" is straight out of a Philip K. Dick science fiction story, but it's not far from reality at this point.

Watch the whole video for more of her insights and to find out what law enforcement will look like ten years from now, when your car tracks your every move and robots swoop down from the sky to prevent you from smoking a joint in the park.

Ars Technica Live is a series of interviews with people doing research at the intersection of technology, culture, and science, conducted by Ars editors Annalee Newitz and Cyrus Farivar at Oakland's premiere tiki bar, Longitude. Want to be part of our live audience? Our next episode will film on June 15, and our guest will be Sarah Jeong, author of The Internet of Garbage. Filming starts at 7:30, but be sure to arrive early to claim a seat and order drinks and snacks.