 He also examined some FBI records for the Church Committee at FBI headquarters.Following this work, and changes made to the Freedom of Information Act in the 1970s, in 1976 Theoharis became a specialist in the history of the FBI.He focused on FBI records procedures, rather than individual FBI targets, leading to discoveries or further understandings of the complexities and uses of FBI office files (as opposed to "official" FBI files), the JUNE mail file, the National Security Electronic Surveillance Index Card File, Surreptitious Entries file, COMPIC file, and COMRAP file.