As a financial advisor for Duke Karl Alexander of Württemberg, he also gained a prominent position as a court Jew and held the reins of the finances in his duchy. He put a duchy monopoly on trade of salt, leather, tobacco and liquor and founded a bank and porcelain factory. In the process he gained a number of jealous enemies who, among other things, claimed that he was involved with local gambling houses.
When his protector Karl Alexander died on March 12 1737, Oppenheimer was arrested and accused of various things, including fraud, embezzlement, treason, lecherous relations with the court ladies, accepting bribes and trying to bring back Catholicism. The Jewish community tried unsuccessfully to ransom him.
Under heavy torture, Oppenheimer broke down and confessed to just about anything he had been accused of. However, when his jailers demanded that he convert to Christianity, he refused.
Joseph Süß Oppenheimer was brought out to the gallows on February 4 1738, and was given a last chance to convert to Christianity; for which he refused; thereafter he was hanged and died on Kiddush Hashem with his last words being the Shema Yisrael. His corpse was gibbeted in a human size bird cage that hung in the public square of Stuttgart for six years, after which his body was finally returned to his family for burial. His story, under the title Jud Süß or Jew Süß was the subject of an 1827 novella by Wilhelm Hauff, a 1925 historical novel by Lion Feuchtwanger, a 1934 British film where he was portrayed by actor Conrad Veidt, and a Nazi propaganda film made in 1940 by Veit Harlan where he was portrayed by actor Ferdinand Marian.