Secretly tagging someone with a GPS with no warrant seems like a pretty clear-cut violation, just as it would be to use a device that collected audio data rather than location.
The law on records from all those cell phones is more confused – by the Patriot Act and various extensions, exceptions and let's-ignore-the-law decisions by various federal agencies in both the Bush and Obama administrations in the years since the 9/11 terrorist attacks.
The WSJ used court records and open-documents requests to document more than 1,000 instances of police tracking cell-phone data last year – records that show rapid growth in the number of examples.
The LAPD tracked 295 phones last year, for example. That's 35 percent more than 2009, the Journal reports. Miami-Dade police increased their tracking by 27 percent. Federal prosecutors in the Southern District of Florida used cell tracking 8 percent more often in 2010 than 2009.
Honestly, how many people could they be watching? 50? 100? 200?
There are 327 million cell phones in use in the U.S.
Cell phone carriers get an "astronomical" number of requests from police for customer phone records according the WSJ's citation of testimony given by cell-phone-company lawyer Al Gidari to the House Judiciary Committee last year.
There are more than 10,000 police agencies with subpoena power, all interested in getting phone records to help in investigations, he said. Of all the telecommunications service companies, only Google admits how many requests it gets for user records.
It's not unusual for carriers to receive a new request that a phone be tracked every 15 minutes, according to Gidari, who also lectures on location privacy.
The volume of user information collected by government is astonishing, but largely unreported. Only Google publicly reports the number of governmental requests it receives," Gidari testified. "The number of requests Google receives is dwarfed by the number of requests wireless carriers receive each year." (Here's a PDF of his whole statement.)