US Police use obscure phone tech to track people, sometimes without warrant

Police around the country are using a powerful but relatively inexpensive cellphone tracking tool to solve crimes. And in some cases, they have used it to track people without a search warrant.

All mobile devices are assigned what's called an advertising identification number, a unique code that allows apps with location services to target consumers with promotions.

For as little as $7,500 a year, Virginia-based Fog Data Science offers a service called Fog Reveal that uses that ad-ID to track a device's wanderings, when location services are enabled.

Documents reviewed by The Associated Press show that Fog heavily markets its product to law enforcement. The company promotes what it calls a "pattern of life" analysis, which can stretch back months.

Public records specialist Bennett Cyphers, an advisor with the Electronic Frontier Foundation, calls Fog Reveal "sort of a mass surveillance program on a budget." He and others believe police use of the platform without a warrant is a violation of people's Fourth Amendment rights.

In a written response to The Associated Press, Fog said it cannot disclose information about its customers. The company said it does not access or have anything to do with personally identifiable information and is leveraging commercially available data.

Arkansas prosecutor Kevin Metcalf says Fog simply uses data that people give away for free, and that it is most useful in cases where time is of the essence. Metcalf also leads the National Child Protection Task Force, a nonprofit that combats child exploitation and trafficking. Metcalf said Fog, which is listed as a task force sponsor, has been invaluable to cracking missing children cases and homicides.

Metcalf also shared his Fog account in the 2020 search for a missing nurse. Documents reviewed by AP show it has been used by agencies as diverse as the U.S. Marshals and a sheriff's department in a North Carolina county with just 91,000 residents.