Last month, the U.S. Supreme Court ruled on geofence warrants, restricting their use in tapping into people’s location data. Back when I was a Chicago police officer, I would have signed that kind of warrant without hesitation, and I believe this decision marks the beginning, not the end, of the conversation.
On July 6, 2001, I had been on the job for eight years when two sisters, 10-year-old Tionda and 3-year-old Diamond Bradley, vanished from their apartment near 35th Street and Cottage Grove Avenue. I was working on the North Side, but every cop in Chicago knew. We all wanted to join the search.
How I wished we had drones then. The same thought crossed my mind after the mass shooting at Highland Park’s Independence Day parade in 2022. Drones were available but legally restricted. That law has since changed.
Geofence warrants present the same dilemma in a different form.
The Supreme Court considered the case of a man who robbed a federal credit union in Virginia in May 2019. Investigators ultimately identified him through smartphone location data obtained with a geofence warrant, which allows for the identification of devices within a defined geographic area during a specific period. Through this kind of warrant, the government can learn from a tech company who was in a geofence at the time of a crime.
Before we treat geofence warrants as an unprecedented threat to liberty, let’s be honest: Investigative dragnets have always existed. If someone commits a serious crime inside a crowded stadium, investigators pull ticket records, surveillance footage and parking data. Nobody calls that shocking. Everyone calls it doing the job. Police have always cast nets. The real question is what happens when the net becomes invisible, instantaneous and infinitely deeper than anything investigators could build before.
When investigators obtain location data from your device, they don’t just learn where you were during a robbery. They can access the map of your entire life. Which hospital did you visit, and how often? Which house of worship do you attend? Which political rallies or protests did you appear at? Where do you sleep? Who do you visit late at night?
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A net that catches your whereabouts is one thing. A net that reconstructs your identity is another.
The question is not whether investigators should have powerful tools. They should. The question is whether institutions establish meaningful limits before extraordinary powers quietly become ordinary practice.
I never thought about constitutional doctrine when I was working a crime scene. I thought about closing the case. That’s exactly the problem. The legal framework governing what investigators can access has never been part of street-level training. It’s assumed. And assumptions about digital data are dangerous when the tool reconstructs an entire life rather than simply placing someone at a scene.
The Supreme Court has tried to keep pace with technological change, recognizing in Carpenter v. United States that long-term location tracking reveals what Justice John Roberts called the “privacies of life.” But court decisions set constitutional floors. They don’t build operational frameworks.
That distinction matters more than ever now. In 2023, Google changed its data storage policies, making future compliance with geofence warrants effectively impossible. Whatever investigative technology comes next will present similar questions unless Congress acts first.
Given this context, the constitutional answer is not to ban geofence warrants but to confine them. A bank robbery justifies examining devices within a reasonable geographic radius of the bank during a defined time window. Not the whole city. Not the whole day. Police can search a specific house named in a warrant, not every house on the block. They can seize records connected to a crime, not conduct unlimited fishing expeditions. The digital realm should follow the same principle, but with guardrails that reflect what digital searches actually reveal.
I’ve seen this pattern before. Drones met community resistance, privacy concerns, surveillance fears and questions about footage retention. Now, some municipalities dispatch them as observation tools. License plate readers and facial recognition followed the same arc. Each arrived with promises of limited use but expanded quietly over time.
That’s not a conspiracy, it’s just the truth. Every category of crime has victims who make morally compelling arguments for expanding the tools used to solve it.
The question is not whether today’s investigators will abuse geofence warrants, but whether the framework being built now can survive in less scrupulous hands tomorrow. A different administration. A private contractor with access to the data. A department with no meaningful oversight. History suggests the framework rarely holds without explicit statutory limits.
The Constitution doesn’t have a “but what about the two girls” exception and it shouldn’t. But that doesn’t mean geofence warrants can never exist. The court has taken an important constitutional step, but courts set floors. Congress and police agencies must build the framework above them: narrow geography, serious crime only, judicial oversight, deletion of uninvolved data, accountability for misuse.
I would have signed that warrant to find the two girls and for Highland Park. I think most investigators would have done the same. That is precisely why guardrails matter. The hardest constitutional decisions are not made when the stakes are low. They are made when the need feels overwhelming. Our responsibility is to ensure advancing technologies continue to serve both justice and liberty long after today’s emergency has passed.
Louis Martinez, a retired Chicago Police Department officer, is a criminal justice professor and unmanned aircraft systems coordinator at Oakton College and author of “The Violent Brain: A Study in Neurocriminology.”
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