View source for Departure from statements by State witnesses (Zimbabwe)

The prosecutor stands in a special relation to the court, and where there is a serious discrepancy between the statement of a State witness taken during investigations and what he says on oath at the trial, the court has the right to expect that the prosecutor will, of his own motion, direct attention to this fact and, unless there is special and cogent reason to the contrary, that he will make the statement available to the defence for cross-examination. On the other hand, a prosecutor is fully justified in refusing to show the statement to the defence where there is no foundation for the suggestion that the witness has materially altered his story.

Where there is such a serious discrepancy the prosecutor should complete the examination of witness and say to court that in the interests of justice he is obliged to draw attention of court to the fact that the statement given by the witness in court is radically different from that which he gave to the police: Steyn 1953 SR 76 at 79; Wise 1975 (2) RLR 194 (A). But it would not be necessary for the prosecutor to mention serious discrepancies if these favour the accused.  See The Prosecutor's Handbook pp 90-92.