Non-Expert Opinion Evidence
Opinion evidence can be an important tool in assessing impressions about facts, community standards, effects and characteristics. However, the rules of evidence must be carefully considered where opinion evidence is relied upon. In general, a witness is required to testify as to what he or she observes and should not give their opinion. The basic rule is that opinion is not admissible as evidence.
However, the rules of evidence permit a witness to express an opinion in certain circumstances. For example, as is often done in planning matters, witnesses with specialized knowledge (typically considered expert witnesses) may give opinion evidence where their evidence is wholly or substantially based on the person’s training, study or experience.
A Court or Tribunal may admit an opinion expressed by a non-expert witness where:
“a) The opinion is based on what the person saw, heard or otherwise perceived about a matter or event; and
b) Evidence of the opinion is necessary to obtain an adequate account or understanding of the person’s perception of the matter or event.”
‘Opinion’ is not defined in the Evidence Act 2008 (Vic), but the term has been judicially defined as ‘an inference from observed and communicable data’.
This definition was discussed in the context of non-expert opinion evidence by the High Court, with the observation that:
“The common law permitted the reception of non-expert opinion evidence where it was very difficult for witnesses to convey what they had perceived about an event or condition without using rolled-up summaries of lay opinion – impressions or inferences – either in lieu of or in addition to whatever evidence of specific matters of primary fact they could give about that event or condition. The usual examples are age, sobriety, speed, time, distance, weather, handwriting, identity, bodily health and emotional state, but a thorough search would uncover very many more.
“[I]n many cases, to endeavour to describe the primary facts underlying the inference may be ineffective or misleading without stating the inference. The reason why it is very difficult for the observer is that it is almost impossible to separate the inferences from the primary facts on which they are based, and often very difficult to identify and recollect the primary facts themselves.”
This passage highlights why opinion evidence is important. It enables a court to gather information regarding the impressions or inferences about matters of everyday life, including subtle social and personal elements.
Opinion evidence at all levels must be carefully and cautiously treated. If it falls outside the exception in the Evidence Act, it may not be admissible.
18 June 2014
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 s79, Evidence Act 2008 (Vic).
 s76, Evidence Act 2008 (Vic).
 Allstate Life Insurance Co v Australian and New Zealand Banking Group Ltd (No 5)  136 ALR 627; applied Full Federal Court in Bank of Valletta PLC v National Crime Authority  165 ALR 60, at  and High Court, in the context of a similar piece of legislation in NSW: s79, Evidence Act (NSW), in Lithgow City Council v Jackson  244 CLR 352, at .
 Lithgow City Council v Jackson  244 CLR 352, per French CJ, Heydon and Bell JJ at .