In August 2011 the ACLU issued public documentation requests to over 380 state and local law enforcement agencies and revealed that virtually all the departments that answered tracked telephones, most without warrants. 

The majority of the 200 agencies that responded engaged in some cellphone tracking. Only a few those claimed they constantly seek warrants and demonstrate possible cause before tracking cellphones, according to the ACLU report. 

Most law enforcement agencies said they track telephones to research crimes, while others stated that they use tracking only in emergencies like a missing folks case. Only ten agencies asserted they never use telephone tracking. 

Some law enforcement agencies provided enough paperwork to paint a detailed image of phone tracking activities. For instance, Raleigh, North Carolina, tracks hundreds of cellphones per year based on invoices from telephone corporations. In Wilson County, North Carolina, police obtain historical tracking information where it's "relevant and material" to an ongoing enquiry, the standard the ACLU notes is lower than probable cause. 

Police in Lincoln, Nebraska, obtain GPS location data on phones without demonstrating likely cause. GPS location info is far more precise than cell tower location info, according to the ACLU. 

Similarly, the ACLU observes that cellphone tracking has gotten so common that phone companies have manuals that explain to police what information the corporations store, how much they bill for access to data and what's needed for police to access it. 

But some law enforcement agencies do seek warrants and likely cause before tracking cellphones. Police in the County of Hawaii, Hawaii, Wichita, Kansas and Lexington, Kentucky, do seek a warrant and likely cause. 

The ACLU says that if "police departments can protect both public safety and privacy by meeting the warrant and possible cause requirements, then certainly other agencies can as well." 

Tags: ACLU, GPS, Warrant-less search