 Between 1980 and 1981 she was enrolled at the Kenya School of Law for the statutory post graduate law course that is a prerequisite to admission to the Kenyan roll of advocates and licensing to practice law in Kenya.After graduating, from 1981 to 1987 Karua worked as a magistrate in various courts including those at Makadara, Nakuru and Kibera, receiving credit for careful discernment.In 1987, she left to start her own law firm, Martha Karua & Co.