ABSTRACT
This chapter deals with reasons for excluding evidence that are unlike any previously encountered. Other exclusionary rules or principles have as the reason for their existence the need to secure a fair trial. Relevant evidence can be excluded because it is likely to mislead the jury1 or because it would have an adverse effect on the fairness of the proceedings.2 The justification for the rules relating to privilege and public interest immunity has nothing to do with the fairness of the trial but with some other benefit that is thought to be more important. The rules about privilege and public interest immunity acknowledge that the public have interests that must occasionally be allowed to prevail over their interest in securing fair trials at which all relevant and otherwise admissible evidence can be heard. Although these topics have this understanding in common, they operate differently. A privilege is a right which the law gives to a person allowing him to refuse to testify about a particular matter or to withhold a document. Effect is given to public interest immunity by means of a power which the
courts have to exclude evidence on the ground that disclosure of information would be damaging to the general good.
