The Senate has spent the past three years investigating the CIA's detention and enhanced interrogation techniques for the period beginning in 2002 after 9/11 and the start of the war in Afghanistan and ending in 2009 when incoming President Barack Obama banned the use of torture. The controversial practices included waterboarding, stress positions, forced nudity, beatings and sleep and sensory deprivation as well as the "rendition" or extra-legal extradition of terror suspects to a network of secret prisons.

The report runs to almost 6,000 pages and is based on more than 6 million pieces of information. Feinstein has said that the report is "comprehensive, it is strictly factual, and it is the most definitive review of this CIA programme to be conducted".