Complex sentence: In 1931 he became Commissar of Justice and Prosecutor General of the RSFSR, in which capacity he served as the chief prosecutor at the Moscow show trials of the 1920s and the early 1930s and was widely seen as the public face of the Soviet justice system.
Split into simpler sentences: In 1931 he became Commissar of Justice and Prosecutor General of the RSFSR. In this capacity he served as the chief prosecutor at the Moscow show trials of the 1920s and the early 1930s and was widely seen as the public face of the Soviet justice system.