FBI taps cell phone mic as eavesdropping tool

The FBI appears to have begun using a novel form of electronic surveillance in criminal investigations: remotely activating a mobile phone's microphone and using it to eavesdrop on nearby conversations.

The surveillance technique came to light in an opinion published by U.S. District Judge Lewis Kaplan. He ruled that the "roving bug" was legal because federal wiretapping law is broad enough to permit eavesdropping even of conversations that take place near a suspect's cell phone.

Kaplan's opinion said that the eavesdropping technique "functioned whether the phone was powered on or off." Some handsets can't be fully powered down without removing the battery; for instance, some Nokia models will wake up when turned off if an alarm is set.