Expert testimony, opinion, argument and the rules of evidence

Expert evidence in contemporary litigation often goes beyond inference as to past or future events based on proven facts. Some classes of so-called expert evidence amount to little more than observation. In some cases, particularly economic statutes, expert opinions may be evaluative and offer characterisations of factual circumstances for the purpose of applying statutory terms, particulalry economic concepts. Such testimony may be characterised to some degree as argumentative in character. The article discusses the various classes of expert evidence and the application of the "basisrule" in relation to such evidence under s 79 of the Evidence Act 1995 (Cth). It considers United States and Canadian approaches to expert testimony particularly in relation to economic evidence. It considers also the line between permissible "argument" and impermissible advocacy on the part of experts.