Chatrie v. United States · ¶68

The warrant issued here, as described earlier, was an uncommon, multi-step one. See supra, at 7–8. The first step it laid out authorized police officers to obtain location data for all cell phones inside the designated geofence within a one-hour timeframe. The second step entitled the officers to obtain additional data (two hours, both inside and outside the geofence) for a subset of those phones—of the officers’ own choosing. And the third step enabled them to obtain personal identifying information (including names, email addresses, and phone numbers) for a further subset— again of their selection. As to how the officers would make their choices at the second and third steps—how they would pick the users subject to more intense scrutiny—the warrant said very little. In toto: They would “attempt to narrow down the list by reviewing the time stamped location coordinates for each…

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