Mutembei is also an Advocate of the High Court of Kenya with a strong background and vast experience as a legal practitioner in a career spanning thirty six years, twenty seven of them as a public officer in the Judiciary. Currently he is the Managing Partner, Mutembei Chabari & Company Advocates.
Away from the work environment, Mutembei has a strong background of pursuing matters of social justice, community welfare and protection of the rights of all individuals. He has previously served as Chairman, Board of Management of Chogoria Girls High School and Kajiunduthi High School. He is a board member of PCEA Chogoria Hospital and has also served as a Director of the Presbyterian Foundation of the PCEA.