Jean-Claude Pressac

Jean-Claude Pressac (3 March 1944 – 23 July 2003) was a French pharmacist by profession, who became a published authority on the Auschwitz concentration camp homicidal gas chambers deployed during the Holocaust in World War II. He was the author of the 1989 book ''Auschwitz: Technique and operation of the gas chambers'' among other publications on the subject, which demonstrated the technical possibility of mass killing by gas chambers during the Holocaust, thus debunking many falsehoods promoted by Holocaust deniers.

Pressac was originally a Holocaust denier who, with Robert Faurisson, attempted to disprove what he considered historically inaccurate depictions of the concentration camps as extermination camps. However, upon visiting Auschwitz in 1979 and 1980, Pressac was able to view first-hand the extensive archive of original German documents thanks to the courtesy of the museum staff and administration unaware of the true purpose of his research, and quickly realized that Faurisson and other Holocaust deniers were wrong. Provided by Wikipedia