A "disturbing" number of law enforcement agencies track cell phones without a warrant, the American Civil Liberties said on Monday, citing documents gathered from across the United States.
"The overwhelming majority of law enforcement agencies that responded engage in at least some cell phone tracking," the ACLU said in a summary of information it gathered. "Even those that have not tracked cell phones in the course of a criminal investigation have tracked cell phones in emergencies, for example to locate a missing person."
Civil liberties advocates have said they believe law enforcement concerns have prevented Congress from updating privacy laws to reduce warrantless tracking and searches.
Of the more than 200 law enforcement agencies that responded to the ACLU's requests, 10 reported that they had never used cell phones to track anyone.
Most police organizations sought the data from phone companies, although some cities, like Gilbert, Ariz., have purchased their own tracking technology, the ACLU reported.
"The government should have to get a warrant before tracking cell phones," ACLU staff attorney Catherine Crump said in a statement. "The fact that some law enforcement agencies do get warrants shows that a probable cause requirement is a completely reasonable and workable policy, allowing police to protect both public safety and privacy."
A patchwork of different laws has created "chaos" for citizens and phone companies, the Center for Democracy and Technology's Jim Dempsey said.
"The report documents what we've suspected all along: Cell phone tracking is widespread and, while some police departments are doing the right thing and getting a warrant, many are not," he told National Journal by e-mail. "The law simply hasn't kept up."