 In 2011, in the case of Daniel David Rigmaiden in the U.S. District Court of Arizona, the chief of the FBI Tracking Technology Unit wrote an affidavit defending the use of an unspecified pen register device.Information about the model or function was purposefully withheld, citing FBI policy; the letter assured the court that the device was legally compliant.A widely cited story released by the Wall Street Journal described the device was described as a "stingray", along with basic information about how it worked.