A special US prosecutor has been appointed to head a criminal probe into alleged CIA abuse of terrorist suspects.On Monday, newly declassified documents revealed that interrogators had threatened to kill one terror detainees’ children and sexually assault the mother of another. The release of the files coincided with President Barack Obama decision to create a new specialist interrogation unit to get information from terror suspects. That will be overseen by the FBI, further sidelining the CIA. In the meantime, Prosecutor John Durham has been charged with investigating the spy agency’s interrogation practices. Amrit Singh from the American Civil Liberties Union said: ‘‘This report only underscores the need for a full scale criminal investigation into not just low level interrogators who went beyond what the Bush Administration authorised, but also to high level officials who set in place the parameters for the CIA’s torture of prisoners, the parameters that were flagrantly in violation of the law.’‘ Officials from the Bush Administration, including Vice President Dick Cheney, deny torture took place saying interrogation techniques yielded vital information. The politically sensitive probe into prisoner abuses comes at a crucial time for Obama as he seeks to overhaul America’s healthcare system.