Rule 30.1.01(1) of the Rules of Civil Procedure states that all parties and their lawyers are deemed to undertake not to use evidence, which is usually documents or other written information, obtained in discovery for any purposes other than the proceedings in which they are obtained. It essentially provides that evidence obtained under some specific rules of the Rules of Civil Procedure cannot be used for any purpose other than the legal proceeding in which the evidence was obtained. This rule would also apply by analogy to family law Applications under the Family Law Rules.
There are some exceptions to the prohibition on ulterior use, including the exception that allows evidence from one proceeding to be used in another to impeach the credibility of a witness. The reason behind the rule is that if a party is promised that documents or other information, including answers to questions will not be used for collateral or ulterior purposes, he or she will be encouraged to give a more complete and honest examination.
The deemed undertaking rule does not apply to evidence given on cross- examination; it applies only to evidence given under Rule 30 (documentary discovery), Rule 31 (examination for discovery), Rule 32 (inspection of property), Rule 33 (medical examination) and Rule 35 (discovery by written questions). It also does not apply in a proceeding commenced by way of Application, except a family law case under the Family Law Rules.
Even where the deemed undertaking rule applies, Rule 31.1.01(8) permits the court to order that it be dispensed with “if satisfied that the interest of justice outweighs any prejudice that would result to a party who disclosed the evidence”. The deemed undertaking rule is largely misunderstood, primarily because most litigants, and even some lawyers, are under the mistaken impression that it applies more broadly than it does.