Civil liberties groups in the US are demanding that the Department of Justice cough details of its use of mobile phone tracking - particularly how often it's done so without probable cause of a crime being committed.

A federal court action has been filed by the American Civil Liberties Union (ACLU) and the Electronic Frontier Foundation. The two groups are are asking for details of all investigations involving mobile phone tracking, though they're particularly interested in cases where courts haven't been involved.

"The information now in the public domain suggests that [the DOJ] may be engaging in unauthorized and potentially unconstitutional tracking of individuals through their mobile phones," claims the complaint.

The problem seems to be that the US lacks a rigid procedure for accessing such information. In the UK the Regulation of Investigatory Powers Act sets out detailed rules for how much information the police can get, and how they get it. One might argue that the process is still too open, or that having cost as the principle controlling force against misuse is unwise, but at least it's a formal and open process.

In the US things are much more murky, and the ACLU claims its only aim is to clear the air. "This is a critical opportunity to shed much-needed light on possibly unconstitutional government surveillance techniques," said Catherine Crump, a staff attorney at the ACLU, "Signing up for cell phone services should not be synonymous with signing up to be spied on and tracked by the government."

Computer World spoke to the DOJ on the matter, and received the usual "if you have nothing to hide you have nothing to fear" line, highlighting how important phone records can be in tracing children and serial murderers - but not terrorists, this time, so missing a trick there.

No one is denying that bad guys can be caught using mobile phone records. But access to such privileged information needs to be controlled by open procedures - trust in a benevolent Department of Justice isn't really sufficient. ®