Former police data analyst Davin Hall uses the Waze navigation app while driving through Greensboro, N.C., on Wednesday, June 22, 2022. Hall quit the city's police force in part over its use of Fog Reveal, a powerful cellphone-tracking tool that the company says uses data from apps like Waze to track mobile devices. A Waze spokesperson said the company has not heard of Fog and has no relationship to it.AP Photo/Allen G. Breed

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.

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