Monday, August 22, 2011

The relevance of expert opinion

Thanks to Peter Tillers in New York for drawing our attention to a High Court of Australia decision which includes discussion by Heydon J of an interesting point about expert evidence: Dasreef Pty Ltd v Hawchar [2011] HCA 21 (22 June 2011).

The joint judgment of French CJ, Gummow, Hayne, Crennan, Kiefel and Bell JJ did not analyse the issue in a way that made it necessary to address the point I will mention below (41), because these judges decided that in this case the testimony offered as expert opinion was not based on the witness's specialised knowledge based on training study or experience. That requirement for admissibility being absent, they held that the trial judge had no evidence to support the conclusion he reached.

Heydon J, on the other hand, was of the view that the evidence legislation, although silent on the point, did leave room for its application. So what was the point? It was: is it necessary that there be evidence of facts upon which it is proposed that an expert should base an opinion, before the expert gives evidence of that opinion? Or, can the expert be called and give evidence of that opinion, on the understanding that evidence will subsequently be called to establish the relevance of that opinion? At 121-127 Heydon J explains why there should be a rule that relevance be established before the expert evidence is adduced.

It seems that the legislation in New Zealand leaves open the possibility that the rule favoured by Heydon J may not apply: s 25(3) of the Evidence Act 2006. Also, s 14 provides for provisional admission of evidence.

This would surely be a matter for the judge's discretion, and would depend on how practical it would be to deal with expert evidence that had been given but which was subsequently found not to be admissible. In judge alone trials it would not be likely to matter, but in jury trials questions of fairness may arise if there was a real risk that the jury would be rendered partial as a result of having heard the inadmissible evidence.