Matthew Guariglia and Lisa Femia of EFF write:
Being out in the world advocating for privacy often means having to face a chorus of naysayers and nihilists. When we spend time fighting the expansion of Automated License Plate Readers capable of tracking cars as they move, or the growing ubiquity of both public and private surveillance cameras, we often hear a familiar refrain: “you don’t have an expectation of privacy in public.” This is not true. In the United States, you do have some expectation of privacy—even in public—and it’s important to stand up and protect that right.
How is it possible to have an expectation of privacy in public? The answer lies in the rise of increasingly advanced surveillance technology. When you are out in the world, of course you are going to be seen, so your presence will be recorded in one way or another. There’s nothing stopping a person from observing you if they’re standing across the street. If law enforcement has decided to investigate you, they can physically follow you. If you go to the bank or visit a courthouse, it’s reasonable to assume you’ll end up on their individual video security system.
But our ever-growing network of sophisticated surveillance technology has fundamentally transformed what it means to be observed in public. Today’s technology can effortlessly track your location over time, collect sensitive, intimate information about you, and keep a retrospective record of this data that may be stored for months, years, or indefinitely. This data can be collected for any purpose, or even for none at all. And taken in the aggregate, this data can paint a detailed picture of your daily life—a picture that is more cheaply and easily accessed by the government than ever before.
Because of this, we’re at risk of exposing more information about ourselves in public than we were in decades past. This, in turn, affects how we think about privacy in public. While your expectation of privacy is certainly different in public than it would be in your private home, there is no legal rule that says you lose all expectation of privacy whenever you’re in a public place. To the contrary, the U.S. Supreme Court has emphasized since the 1960’s that “what [one] seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.” The Fourth Amendment protects “people, not places.” U.S. privacy law instead typically asks whether your expectation of privacy is something society considers “reasonable.”
This is where mass surveillance comes in.
Read more at EFF.