What 'Reasonable' Used to Mean
The Fourth Amendment protects you only where you have a 'reasonable expectation of privacy.' That test was meant to expand your rights. Increasingly, it does the opposite.
In 1967, the Supreme Court decided Katz v. United States and, almost in passing, rewrote how Americans would be watched for the next half-century. The government had recorded Charles Katz placing bets from a public phone booth without a warrant. The Court ruled the recording unconstitutional, and Justice Harlan, in a concurrence, gave us the test that still governs nearly every surveillance question today.
You are protected, Harlan wrote, where you have an expectation of privacy that society is prepared to recognize as reasonable.
It sounded like a shield. In practice, it has become a ratchet.
The trap inside the test
The problem is the word reasonable. Whether your expectation counts is measured against what society already accepts, and society's expectations are shaped by the very technology the test is supposed to constrain.
Each new surveillance tool, once deployed widely enough, quietly resets the baseline. The first license-plate reader is novel and alarming. The ten-thousandth is just how policing works now. And once a practice is normal, a court can say, with a straight face, that no one could reasonably expect privacy from it.
The doctrine eats itself. The more we are watched, the less the Constitution says we can object.
Third parties, and the data you "chose" to share
The erosion accelerated with a second idea: the third-party doctrine. Under cases like Smith v. Maryland, information you hand to someone else (your phone company, your bank) is no longer something you can expect to keep private. You "assumed the risk" that they might share it.
In 1979, that meant the numbers you dialed. Today it means:
- everywhere your phone has been, logged by your carrier
- everything you've searched, bought, or asked an AI assistant
- the faces, plates, and movements captured by cameras you never agreed to
The fiction is that you chose to share all of this. The reality is that participating in modern life is not a choice, and the "third parties" now hold a near-complete record of your existence.
The crack in the wall
There is reason for cautious hope. In Carpenter v. United States (2018), the Court finally blinked: accessing 127 days of someone's cell-site location data, it held, is a search requiring a warrant, third-party doctrine or not. The majority recognized that some technologies are so revealing that the old rules simply break.
Carpenter is narrow. But it establishes the principle that matters: the Constitution can adapt to technology instead of surrendering to it. The question is whether that principle spreads, or stays quarantined to one kind of data while everything else slips through.
Why this is the whole fight
Every story we cover on this channel runs back to this one doctrine. Facial recognition, automated license-plate readers, data brokers, predictive policing: each is, at bottom, an argument about what you can reasonably expect.
If the answer keeps shrinking toward nothing, the Fourth Amendment becomes a promise with no territory left to defend.
So the work is twofold. Refuse to let the baseline reset quietly: name each new tool while it is still strange enough to alarm. And demand, in courts and city councils, that reasonable be defined by the rights we mean to keep, not merely by the surveillance we've been made to tolerate.
That is what this Dispatch is for.