For Congress, a Question of Cellphone Tracking

While the Senate considered an overhaul of a sweeping quarter-century-old law governing e-mail privacy, a House Judiciary Committee panel received dueling arguments over when and how police can track the location of Americans carrying a cellphone.

For investigators, knowing where a suspect is and at what time can be crucial to an investigation. Cellphones have become a powerful tool for establishing those facts — one detective scheduled to testify on Capitol Hill described them in prepared remarks as a “witness” to a crime. Less clear is the law on how authorities can extract that information from cellphones. Law enforcement officials say procuring a search warrant, based on probable cause, is too time-consuming and slows down an investigation. The law is vague on what information cellphone carriers must turn over to law enforcement and whether the officials require judicial review. Under what circumstances can police obtain a “tower dump,” meaning identify cellphone users whose devices pinged off a particular cellphone tower? Should a warrant be required to monitor the location of an individual with whom a known suspect is communicating? Should a warrant be required for specific location information of a known suspect? There is no consensus in the law on these questions.