For more than a decade, the United States government had been keeping a secret law enforcement database of international phone calls. The data on the calls were gathered from telecommunications companies under administrative subpoenas.

The database includes information such as the phone numbers that made and received calls, time that the calls were made, and duration of the calls. With these details on hand, investigators were allowed to query numbers under a "reasonable articulable suspicion" and deemed relevant to a federal criminal investigation.

The revelation of the database was made through the order of U.S. District Judge Rudolph Contreras of Washington. The judge was handling the case of a U.S.-Iranian dual citizen charged with the illegal export of non-military technology to Iran. The suspect was tracked down by authorities through the investigative efforts of the Department of Homeland Security.

The judge asked in December for the government to explain the "contours of the mysterious law enforcement database used by Homeland Security Investigation, including any limitations on how and when the database may be used."

The explanation occurred on Thursday, Jan. 15, when Robert Patterson, an assistant special agent at the Drug Enforcement Agency (DEA), officially declared in federal court the details surrounding the investigation that was performed by the Department of Homeland Security. This helped authorities locate the suspect.

Patterson wrote in the declaration filed in the District Court for the District of Columbia that the database "consisted of telecommunications metadata obtained from United States telecommunications service providers pursuant to administrative subpoenas served upon the service providers under the provision of 21 USC 876, a provision of the Control Substance Act that provides law enforcement with the ability to investigate suspected drug crimes."

The database, which existed at the DEA's disposal, had not been used since late 2013. The records didn't have information on the content of the calls nor any personal identification details.

There was no explanation why using the database had to be suspended in September 2013.

According to Patrick Rodenbush, a spokesman for the Justice Department, the database had not been active or searchable and that all of the information had already been deleted. He declined to say whether the DEA was, in any way, collecting other forms of bulk communications data.

Law enforcement in the U.S. can issue administrative subpoenas without seeking approval from the court.

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