Admissibility of expert opinion

Thiess Pty Ltd & Anor v Arup Pty Ltd & Ors [2012] QSC 131

A useful summary of the law…

Applegarth J

Relevant principles of admissibility

[34] The Australian edition of Cross on Evidence summarises the conditions for admissibility of expert opinion as follows:

“First, there must be a field of specialised knowledge. Secondly, there must be an identified aspect of that field in which the witness demonstrates that by reason of specified training, study or experience, the witness has become an expert. Thirdly, the opinion proffered must be wholly or substantially based on the witness’s expert knowledge. Fourthly, the expert must identify the assumptions of primary fact on which the opinion is offered (‘the assumption identification rule’). Fifthly, the opinion is not admissible unless evidence has been, or will be, admitted, whether from the expert or from some other source, which is capable of supporting findings of primary fact which are ‘sufficiently like’ those factual assumptions ‘to render the opinion of the expert of … value’ (‘the basis rule’). Sixthly, it must be established that the facts on which the opinion is based form a proper foundation for it. Seventhly, the opinion of an expert requires demonstration or examination of the scientific or other intellectual basis of the conclusions reached. It is not, however, necessary for the expert’s opinions to be described as such: it is sufficient if in substance they are inferences from assumed facts drawn with the aid of the expert’s expertise. These are rules of admissibility for the judge, although to the extent that the evidence, though admitted, transgresses these criteria they indicate matters material to weight; however, there is no duty on the judge to direct the jury not to use the evidence unless they are satisfied the criteria have been complied with.”[1]

The learned authors of Cross observe that the largely formal character of the tests described is revealed by the fact that the tendering party does not have to establish, to get the evidence received, that the opinion evidence “is in fact intellectually convincing”:

“That is a matter to be decided at the close of the case. The question, when admissibility is under consideration, is whether there is reasoning purporting to justify the expert’s conclusion, not whether the reasoning does justify it. ‘[T]he giving of correct expert evidence cannot be treated as a qualification necessary for giving expert evidence.’”[2]

[35] The requirements that the witness called as an expert must have specialised knowledge based on training, study or experience in a field of specialised knowledge, and that the opinion expressed by the witness must be wholly or substantially based on that knowledge, were discussed recently by the High Court in Dasreef Pty Ltd v Hawchar.[3] That authority was concerned with the requirements for admissibility contained in s 79(1) of the Evidence Act 1995 (NSW). However, the observations of members of the Court are relevant to similar common law requirements that govern admissibility. The Court referred to earlier decisions in relation to legislation that governs the admissibility of expert opinion including Makita (Australia) Pty Ltd v Sprowles.[4] In Makita,[5] Heydon JA (as his Honour then was) considered the basis upon which expert opinion evidence is admissible including the requirement that the opinion proffered must be “wholly or substantially based on the witness’s expert knowledge”.[6] In Dasreef, French CJ, Gummow, Hayne, Crennan, Kiefel and Bell JJ observed in relation to such requirements:

“… that is not to say that the requirements cannot be met in many, perhaps most, cases very quickly and easily. That a specialist medical practitioner expressing a diagnostic opinion in his or her relevant field of specialisation is applying ‘specialised knowledge’ based on his or her ‘training, study or experience’, being an opinion ‘wholly or substantially based’ on that ‘specialised knowledge’, will require little explicit articulation or amplification once the witness has described his or her qualifications and experience, and has identified the subject matter about which the opinion is proffered.”[7]

Brisbane Barrister – David Cormack

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