Sgt Matshepo Twala was elated when the Johannesburg magistrate’s court sentenced the man accused of killing car guard Xolani Meswana to 10 years in jail, ending a difficult four years of fighting for justice.

But now, Twala is facing another mammoth task of finding the family of her star witness, Samuel Diseko, whose evidence single-handedly nailed the accused, Philani Mkhulisa...