As a partner of Webb, Low and Barry, Coltart handled many human rights cases relating to the Gukurahundi genocide in Matabeleland between 1983 and 1987. In 1986, Coltart authored a detailed report concerning human rights abuses in Matabeleland during 1985, which was submitted to the Minister of Justice and the Governor of Matabeleland North. During this time, Coltart represented various opposition PF ZAPU Central Committee members detained by the ZANU PF government, including Sidney Malunga, Edward Ndlovu and Stephen Nkomo (brother of ZAPU leader Joshua Nkomo).