Require Police to Get a Warrant to Search ALPR Data | Hacker News Reader

Require Police to Get a Warrant to Search ALPR Data

eff.org

27 pointsspeckx11 comments

As much as I'd love for this to happen, the analogue of ALPRs is a cop following someone all day (no warrant required) or an army of cops on street corners writing down every license plate that passes (no warrant required). Just because it's a computer doing the reporting, how does that suddenly make it a fourth amendment violation?

Cops can't wiretap without a warrant because a phone call is a private conversation between two people in a private space. A cop is allowed to stand next to you while you chat on a park bench or hear your side of a cellphone conversation.

Cops can't gain access to your email without a warrant because those are your private papers, explicitly called out in the fourth amendment. Just like they can't open your incoming and outgoing snail mail. However, cops can look at mail covers with a non-warrant approval just like they can see email metadata without a warrant simply because everyone else can see that mail cover or metadata.

A license plate is not private information. It's bolted on to your car in at least one place and is designed to be very visible from a distance. Public roads are in the public and you do not have a reasonable expectation to privacy driving around on public roads (the contents of your car is different). Since your license plate, and possibly your face, are in plain view in the public, how can we effectively protect ALPR data by requiring warrants?

It would be much easier to try to require a subpeona or court order to obtain ALPR data. Even the data created by ALPRs on cop cars should still require a court order except in extreme cases like tracking a violent suspect or a missing person.

> how does that suddenly make it a fourth amendment violation?

The database containing a persons travel history is the violation, as I understand it.

This database can be used to stalk someone and disrupt their life by anyone that has access to it.

Its happened to me personally.

Whereas, a simple snap of a speeding cars plate to send the owner a ticket, says nothing about their actual life, personal and business connections, etc.

I can see that as an argument, it's the patterns that ALPR data produces which could become an invasion of privacy, not the actual photos themselves. However, how is this any different than a cop legally following your car around all day?

This is a good question for an attorney.

But the point remains: a cop writing down license plates on a notepad can build a similar database. And there's plenty of precedence indicating that police don't need a warrant to record observations in public.

A database can be used to stalk someone, but that doesn't make it a 4th Amendment violation. Remember, a cop can just tail you and follow you without a warrant too.

https://www.independent.org/article/2026/08/13/chatrie-flock...

August 13th, 2026

In a ruling that could send ripples through Fourth Amendment law for years to come, the Supreme Court ruled 6-3 in Chatrie v. United States (2026) that law enforcement does indeed conduct a Fourth Amendment search when obtaining a citizen’s location history from a tech company (in this case, Google) via a geofence warrant. Building on the precedent set in Carpenter v. United States (2018), the Court ruled that individuals retain a reasonable expectation of privacy in their cell phone location history. SCOTUS rejected the government’s argument that a short window of surveillance (in this case, two hours) does not constitute a search, and held that even brief periods of tracking can reveal constitutionally protected personal details.

The Chatrie case is really relevant to ALPRS. The Chatrie case involves the government demanding private phone GPS location data from Google. This is not covered by the plain view doctrine because the data they're requesting is fundamentally not collected by observations in plain view.

Unlike the phone GPS location data, ALPRs are cameras set up in public locations recording what anyone with their own two eyes and a notepad could observe.

No, but Google does fall under the third-party doctrine.

If a third party has data about you, then it’s no longer private data and it can be obtained by the police — with a warrant.

The same rule should apply here.

But again, the data isn't private regardless of who collected it. Images taken of public spaces in plain view don't require a warrant to collect.

If they want to pay a cop to follow you around 24x7 and without a warrant, then they should do that. And pay for all that time spent. If it’s not useful or cost-effective to do that, then they need to find a different way to do their job.

If they want to search a database that does all that work for them, then they should at least get a warrant. If that’s too hard for them, then they need to get a different job.

There are a lot of things in this world where a difference in scale becomes a difference in kind. And the rules are necessarily different for changes in scale versus changes in kind.

From the article:

Searches for “LMAO”

Sometimes officers do not even provide a real reason to search stored ALPR data. EFF found officers logging search reasons such as “LOL,” “LMAO,” “idk,” and random keyboard mashing. These entries are supposed to document why a search complies with an agency’s own use policies. A Goshen (Indiana) Police Department officer searched 6,474 networks, representing data from 82,413 cameras, with “idk” as the reason.

An officer who asked a judge for a warrant to track someone for “LMAO” would be laughed out of the courtroom.

Reply on news.ycombinator.com