Koni led the investigation into the 1888 Borki train disaster and presided over the 1878 jury trial against the revolutionary and attempted assassin Vera Zasulich. As a jurist, Koni was instrumental in liberalizing Russian criminal law, notably in the form of the revised criminal code of 1903. As a member of several reform commissions, he defended judicial independence and the trial by jury. Due to his influence, prison sentences were reduced and special establishments for juvenile criminals were introduced towards the end of the 19th century. While he supported the liberals' call for a constitutional order in Russia, he declined an appointment as Minister of Justice in the government of Pyotr Stolypin in 1906.