Describing interrogation techniques and approaches used during the Cold War, an old 1960s CIA counterintelligence interrogation manual advised covertly photographing the interrogation subject and also audio taping his interrogations.

A tape player could free an interrogator from note taking, the CIA’s experts wrote, while also providing a live record of an interrogation that could replayed later. The manual’s author noted that for some of those interrogated, “the shock of hearing their own voices unexpectedly is unnerving.”