Evidence of a fact is that which tends to prove it, and the law of evidence consists of the rules determining what evidence will be admitted in judicial proceedings to prove facts in issue and how it must be given. Irrelevant evidence is never admissible, but not all logically relevant evidence is admissible in Court. There are several types of inadmissible evidence, for example, hearsay and opinions, and there are numerous exceptions in each case. Sometimes public policy forbids the giving of otherwise admissible evidence. One important instance occurs where certain confidential relationships exist. A lawyer may not, without his client's consent, disclose communications made to him in his professional capacity. A similar rule applies in New Zealand to clergymen and, in civil cases only, to doctors. Journalists have no such privilege. Communications to a marriage guidance counsellor are probably protected from disclosure without consent. There is a statutory rule that no disclosure may be made of anything said to a conciliator appointed by the Court in matrimonial proceedings.
Generally, anyone is a competent witness in any proceeding and can be compelled to give evidence for either side. In criminal cases, however, the prosecution cannot call the accused as a witness, nor can it call his spouse, except in a few instances when a spouse is a competent witness for the prosecution. In no case can the witness be compelled to testify against his wife or, in the case of a woman, against her husband.
Evidence is admissible even though it has been obtained by improper means, for example, an illegal search. This rule extends in New Zealand to induced confessions, which are excluded in most other Commonwealth countries, if the Court is satisfied that the inducement was unlikely to cause an untrue admission. In the United States, on the other hand, the argument has prevailed that the best safeguard against the improper obtaining of evidence is to reject it as proof of guilt. The only justification for the New Zealand rule is confidence that improper means of gathering evidence will not ordinarily be used.
One part of the law of evidence deals with the onus of proof and the degree of proof necessary in judicial proceedings. The burden of proving a fact is on the person alleging it. Broadly speaking, it is sufficient in civil cases to show that a fact is true on the balance of probability. In criminal proceedings, however, the prosecution must prove the guilt of the accused beyond reasonable doubt. Where exceptionally the onus of proving a defence is placed on the accused (for example, insanity), he need only satisfy the balance of probability test.
by Bruce James Cameron, B.A., LL.M., Legal Adviser, Department of Justice, Wellington.