Thread by @themarkup

Police can request data on every person’s device in a specific area through something called a “geofence warrant.”

In California, law enforcement agencies appear to be severely underreporting these warrants, @tenuous and @alfredwkng found. themarkup.org/privacy/2021/1…

Geofence warrants are a fairly new concept mostly involving data from Google.

Privacy advocates say they violate civil liberties. For example, the @ACLU found that law enforcement was using geofence data to track Black Lives Matter protesters in 2016. themarkup.org/ask-the-markup…

California is one of few states where law enforcement agencies must disclose geofence warrants to a state dataset.

We looked at that dataset—as well as a geofence transparency report from Google—and found the numbers didn’t add up.

Only 186 warrants that contained the word “Google” had been reported to the state of California in 2020.

Google, on the other hand, said that the company received 1,909 geofence warrant requests from California in that same year.

2019 data revealed a similar pattern.

There are many reasons this could be happening. One factor that both privacy experts and the California Department of Justice highlighted is that agencies can delay reporting a warrant if it’s sealed from the public.

And there are material consequences. The lack of reporting makes it hard for civil liberties advocates to keep tabs on the warrants and fight them.

“... if you don’t know about them, how do you get involved in the cases?” said Jennifer Lynch of @EFF. themarkup.org/privacy/2021/1…