Most witnesses you call will be co-operative and provide helpful evidence for your cause, but you must be prepared for disappointment. Some witnesses will surprise. You expect them to say one thing and in court they cannot recall the evidence or say something completely different. In many cases the inconsistencies or omissions in their testimony are simply the result of nerves and forgetfulness, but in other cases the witness has chosen not to be truthful with you or with the court. The witness has turned on you -has become a turncoat.
Crown prosecutors in particular must be prepared for the turncoat witness. The reality of a criminal prosecution is that the Crown often needs to rely upon the testimony of reluctant, fearful or unsavoury witnesses and it is not unusual for Crown witnesses to be sympathetic to the defence, if not friends or relatives of the accused. Therefore, the focus in this section will be on the applicable law in criminal cases. Fortunately, most of the law is transferable to civil cases.
Available at: http://works.bepress.com/lee_stuesser/8/