Trial advocacy is a bit like battle - not for the feint hearted. Counsel make forensic decisions all the time when running trials. Some calculated decisions will come off and others won't. The real skill of the advocate is to make the right tactical calls to ensure ultimate victory. That skill should never be underestimated.
The adversarial system leaves it to parties to determine what evidence will be called to make or rebut a case. There is no compulsion on a defendant to call any witnesses at all, if its counsel believes that the plaintiff will fail on the evidence presented
A decision by counsel for the plaintiff to withhold certain evidence so as to preserve the ability to surprise the defendant's witnesses with it in cross-examination can backfire, if the defendant then calls no witnesses at all.
That is precisely what occurred in Advanced Fuels Technology v Blythe & Ors (Application to re-open plaintiff’s case)  VSC 250 in which Macaulay J refused the plaintiff's application for leave to reopen its case so as to tender into evidence the documents it had withheld for tactical reasons.
Macaulay J noted that there was no compulsion on a party to call any witnesses and the fact that the defendant had filed Outlines of Evidence for witnesses that it proposed to call did not constitute a final decision to do so. He was not impressed by the plaintiff's argument that the defendants should have warned him that they did not intend to call any witnesses. He said:
' Further, it does not lie well in the mouth of AFT, having masked its intention to rely upon certain evidence by not presenting it during the course of its own case, to complain that the defendants did not volunteer their intention not to call any witnesses before AFT closed its case. Exposing that inconsistency rather neatly, AFT argued it was entitled to the forensic advantage gained by not ‘telegraphing [its] punches’  when it came to cross-examining witnesses yet the defendants were obliged to ‘telegraph an intention as to whether or not they are going into evidence’. '
He also took a robust view of the adversarial system in answer to the argument that the court should ensure that it has before it all relevant evidence. He said:
' Accepting that it is desirable that the court hears the evidence that is relevant to the dispute it must resolve, the adversarial system does not guarantee (or insist) that the court hears all relevant evidence. It is for the parties to choose which evidence they will bring forth to the court and it is for the parties to decide which witnesses they will call. It is not uncommon for a party not to adduce a relevant document or call a relevant witness. The principles in Jones v Dunkel have been developed to cater for that very situation. It may even be that both parties seek to keep out a relevant document because each of them thinks, for different reasons, it will harm their case. The court only hears the evidence the parties produce. If parties make tactical, deliberate decisions not to adduce certain evidence, they are entitled to do so: the court must decide the case without reference to that evidence.'