Chatrie v. United States · ¶27

The warrant application went on to describe the three- step process that the police would follow to obtain the location information sought. At step one, Google would produce anonymized location data for all cell phones within the geofence in the hour between 4:20 and 5:20 p.m. (30 minutes before to 30 minutes after the robbery). At step two, police officers would “attempt to narrow down the list [of devices] by reviewing the time stamped location coordinates for each [device] and comparing that against the known time and location information that is specific to this crime.” 2 App. 136. For that narrowed list, Google would provide additional (but still anonymized) data—cell-phone locations both inside and outside the geofence during a two- hour period (so now from 3:50 to 5:50 p.m.). Finally, at step three, police would again “attempt to narrow down the list by comparing this additional…

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