Gerlach was born in Berlin, Brandenburg. From 1813–15, he fought in the War of the Sixth Coalition, and later pursued a judicial career. Gerlach became Judge of the High Court, or Oberlandesgerichtsrat, in the city of Naumburg in 1823. In 1829, he became Agricultural and Municipal Court Director in Halle. By 1835, Gerlach was the Vice President of the Higher Regional Court in Frankfurt (Oder).