ABSTRACT
The role played by opinion evidence in both criminal and civil trials has been the source of considerable consternation. ‘Opinion’ has been defi ned by the Australian courts as ‘an inference drawn or to be drawn from observed and communicable data’, 1 and this defi nition, although seemingly broad, would appear to be widely accepted. As a general rule, witnesses should only give evidence of facts, since it will be the opinion of the judge or the jury, and not the witnesses that will determine the end result. However, it is not possible to draw a neat dividing line between fact and opinion, and, as such, the law of evidence has developed two different sets of rules for experts and lay witnesses.
