High Quality Content by WIKIPEDIA articles! Gitta Sereny, CBE (13 March 1921 – 14 June 2012) was an Austrian-born biographer, historian and investigative journalist who came to be known for her interviews and profiles of controversial figures, including Mary Bell, who was convicted in 1968 of killing two children when she herself was a child, and Franz Stangl, the commandant of the Treblinka extermination camp.