Jacob Sullum

That rule is considerably more protective than the Justice Department's current policy, which is to seek a warrant only for real-time tracking of cellphones using GPS or triangulation (a technique that helps locate a phone within the sector served by the nearest base station).

But, as Crump observed, "this is a meaningless distinction," since investigators can convert live tracking into historical records simply by waiting a minute or two before looking at the data. In any case, the Justice Department's rule bizarrely implies that examining six months of location records is somehow less intrusive than tracking a cellphone in real time for a day.

Furthermore, as University of Pennsylvania computer scientist Matt Blaze noted in his testimony on the GPS Act, the sectors served by each cellphone base station are becoming smaller and smaller as carriers strive to keep up with increasing demands on their networks. That means it may be possible to identify a target's specific location without GPS or triangulation, simply by knowing the closest base station, which is information cellphones automatically collect.

While the federal approach to cellphone tracking makes little sense, the ACLU reported last month that local policies "are in a state of chaos, with different towns following different rules -- or in some cases, having no rules at all."

Examining documents from more than 200 law enforcement agencies, the ACLU found that only a few had a general policy of seeking a warrant for cellphone tracking. Some do warrantless tracking only in life-threatening emergencies, but many do it routinely.

Our privacy deserves more respect. The GPS Act would provide it.

Jacob Sullum

Jacob Sullum is a senior editor at Reason magazine and a contributing columnist on Townhall.com.
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