Jay defended numerous fugitive slaves in court and helped several gain freedom. In 1852 Jay led a team of attorneys in New York City in "Lemmon v. New York," gaining the freedom of eight Virginia slaves brought to New York by their owners in transit to Texas. The ruling survived appeals through the state courts. In 1854 Jay was among the founders of the Republican Party in the United States. In 1883 he was appointed as the Republican member of the New York Civil Service Commission, founded to reduce patronage and corruption in government, and later was selected as its president.