Richard W. Sonnenfeldt was born Heinz Wolfgang Richard Sonnenfelt to a Jewish family in Berlin, Germany. In 1938, when he was 15, his parents sent him and his younger brother to boarding school in England to escape Nazi persecution. After England entered World War II in 1940, he was interned as an enemy alien, then deported to Australia. On his release, he emigrated to India and then to the USA, where he was reunited with his brother and parents in Baltimore, Maryland. He graduated from high school and was drafted into the U.S. Army. He was then assigned to Europe, where he fought in the Battle of the Bulge and helped liberate the concentration camp at Dachau. At the end of the war, he was working in an Army motor pool in Austria when General William J. Donovan, head of the Office of Strategic Services (OSS), recruited Sonnenfeldt to be his personal interpreter because he spoke German and English fluently. When Gen. Donovan became the first deputy of U.S. Supreme Court Justice Robert H. Jackson, the U.S. Chief of Counsel for the trial of Nazi war criminals at Nuremberg. Sonnenfeldt moved with Donovan into that project, participating in the pre-trial interrogations of prisoners, and serving as the chief interpreter for the prosecution.
In 1946, he returned to the USA and studied electrical engineering at Johns Hopkins University. He went to work for RCA, and was part of the team that invented color television, before becoming a senior executive at NBC. He also served as dean of the Graduate School of Management at the Brooklyn Polytechnic Institute. His memoirs, first published in Germany, were published in English in 2006 as Witness to Nuremberg. He was interviewed for the 2006 BBC docudrama Nuremberg: Nazis on Trial, and many other documentaries.