Its use is seldom mentioned in court cases; one spokesman said, "The success lies in the secrecy."

EFF reports in Inside Fog Data Science, the Secretive Company Selling Mass Surveillance to Local Police:

EFF could not verify Fog's claims. But there is reason to be skeptical: Thanks to the nature of its data sources, it's likely that Fog can only access location data from users while they have apps open, or from a subset of users who have granted background location access to certain third-party apps. Public records indicate that some devices average several hundred pings per day in the dataset, while others are seen just a few times a day.

? TN Editor

Local law enforcement agencies from suburban Southern California to rural North Carolina have been using an obscure cellphone tracking tool, at times without search warrants, that gives them the power to follow people's movements months back in time, according to public records and internal emails obtained by The Associated Press.

Police have used "Fog Reveal" to search hundreds of billions of records from 250 million mobile devices, and harnessed the data to create location analyses known among law enforcement as "patterns of life," according to thousands of pages of records about the company.

Sold by Virginia-based Fog Data Science LLC, Fog Reveal has been used since at least 2018 in criminal investigations ranging from the murder of a nurse in Arkansas to tracing the movements of a potential participant in the Jan. 6 insurrection at the Capitol. The tool is rarely, if ever, mentioned in court records, something that defense attorneys say makes it harder for them to properly defend their clients in cases in which the technology was used.