Many law enforcement agencies across the U.S. track mobile phones as part of investigations, but only a minority ask for court-ordered warrants, according to a report released Monday by the American Civil Liberties Union.
More than 90 law enforcement agencies said they track mobile phones during investigations, but only six of those agencies reported receiving court-approved warrants after demonstrating that there's probable cause of a crime, according to an ACLU report based on public information requests filed by the group last year.
Ten agencies, including the Hawaii Department of Public Safety and the Wyoming Division of Criminal Investigation, told the ACLU they do not track mobile phones.
In most cases, police received subpoenas, typically from clerks of court or prosecutors, to track mobile phones, the ACLU said in its report.
The report raises "disturbing" privacy and civil liberties issues, said Catherine Crump, staff attorney for the ACLU's Speech, Privacy and Technology Project.
"Tracking someone's location is a substantial invasion of their privacy," she said in an email. "To know where a person goes is to know what they value, to know who they are."
Police should get a warrant before tracking mobile phones, Crump said. "The government shouldn't be engaging in such an invasive practice without strong safeguards," she added. "Having to go to a judge and prove that there is probable cause would be such a safeguard."
Among the law enforcement agencies that track mobile phones without warrants, according to the report: police departments in Phoenix; Washington D.C.; Newark, N.J.; Oklahoma City; Albuquerque, N.M.; and Salt Lake City. Several large police departments weren't included in the report.
The ACLU sent public records requests to 380 law enforcement agencies across the U.S. in August 2011, and 205 agencies responded. But about half of the agencies that responded refused to say whether they track mobile phone or gave "unclear" answers, the ACLU said.
Tracking a mobile phone should be held to the same standard as police searching a house, which requires a warrant, said Jim Dempsey, vice president for public policy at the Center for Democracy and Technology, a digital rights group.
The ACLU report represents a "clear confirmation" of the suspicion by several civil liberties and other groups that many police departments aren't getting warrants to track mobile phones, Dempsey said. "The government should be required to comply with what we think the [U.S.] Constitution requires, which is to get a warrant from a judge, except in emergency cases," he said.
For the last two years, the ACLU, CDT and several other groups, along with AOL, Amazon.com, Google, Microsoft and other companies, have been pushing for the U.S. Congress to rewrite the 26-year-old Electronic Communications Privacy Act, which governs law enforcement access to digital communication. The groups say the law is outdated and treats digital data inconsistently.
Three bills in Congress would require warrants for mobile phone tracking, but the legislation hasn't moved forward.
The ACLU report shows "widespread confusion about what the law actually requires," Dempsey said.
Crump agreed, saying that in some cases, police are tracking the people who call the mobile phone of someone they are investigating. "That means if a suspected criminal calls his mother or orders a pizza, the police also track the mom and the pizza delivery person," she said. "A huge number of innocent people get swept up in the tracking, and that's not the sort of targeted and tightly controlled use of an invasive practice that ought to be in place."
The law about tracking mobile phones is "in a state of chaos," she added. "In some places police do get warrants and demonstrate probable cause," she said. "But in others, the police don't involve a court at all."
The U.S. Department of Justice has questioned the need for changes to ECPA, saying quick access to information such as mobile-phone tracking data can save lives.
The ACLU report also raises concerns about the length of time that mobile carriers retain customer location information. Verizon Wireless keeps records for one year, Sprint Nextel for 18 to 24 months, and AT&T has retained location data since July 2008, according to information supplied to the ACLU by one police department. That retention of data is not disclosed in privacy policies, the ACLU said.
Representatives of the three carriers did not immediately respond to requests for comments.
Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is firstname.lastname@example.org.