The prosecution should generally call all apparently credible witnesses whose evidence is admissible and essential to the complete unfolding of the prosecution case or is otherwise material to the proceedings. Unchallenged evidence that is merely repetitious should not be called unless that witness is requested by the accused.
If a decision is made not to call evidence from a material witness where there are identifiable circumstances clearly establishing that his or her evidence is unreliable, the prosecution, where the accused requests that the witness be called and where appropriate, should assist the accused to call such a witness by making him or her available or, in some cases, call the witness for the purpose of making him or her available for cross-examination without adducing relevant evidence in chief (see Rule A.66B(j) of the Solicitors Rules - Appendix B).
Mere inconsistency of the testimony of a witness with the prosecution case is not, of itself, grounds for refusing to call the witness. A decision not to call a witness otherwise reasonably to be expected to be called should be notified to the accused a reasonable time before the commencement of the trial, together with a general indication of the reason for the decision (eg. the witness is not available or not accepted as a witness of truth). In some circumstances, the public interest may require that no reasons be given. Where practicable the prosecution should confer with the witness before making a decision not to call the witness.
There should be disclosure of any information, including any criminal convictions, in the possession of the prosecutor that reflects materially on the credibility of a prosecution witness or where cross-examination based upon it might reasonably be expected to materially affect that credibility.
The mere unwillingness or unavailability of a witness to testify is not ordinarily required to be disclosed unless the matter proceeds to a contested hearing.
Any immunity (indemnity or undertaking) - granted or approved in principle - or inducement provided to a prosecution witness should be disclosed to the accused in advance of the trial.
Child witnesses are to be treated, so far as practicable, consistently with the provisions of the UN Convention on the Rights of the Child (excerpts from which are Appendix G).