Case: HG v The Queen [1999] HCA 2 ; (1999) 197 CLR 414 
Outcome: discussed
That leads to the next basis of objection, that there has not been laid out a sufficient body of reasoning and assumptions to ground the admissible reception of the evidence. It is necessary to be clear about the legal framework in which I am dealing with this question. I begin with the judgment which I wrote in 2003, not because of any reason other than that it is a convenient starting point. In Evans Deakin Pty Ltd v Sebel Furniture Ltd [2003] FCA 171 , at [68] and following, I said some things about expert evidence. It is important to understand the context of what I wrote, as it is always important to understand the context of the reasons of judges. As can be seen from a discussion of the subject of the objection in that case (and once again with respect to the author of it, who is identified in that case) the expert report was a complete muddle of fact, assertion and opinion that was grounded in common sense only, if that, and with some very minor body of expert opinion sprinkled through over 300 paragraphs. It reflected a trend which is, probably since Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305 ; (2001) 52 NSWLR 705 and HG v The Queen [1999] HCA 2 ; (1999) 197 CLR 414 and other cases, somewhat on the wane, of throwing together litigation support reports and tendering them to judges on the basis that the discursive opinions of former auditors and accountants about how damages should be assessed in any particular case should be given weight. That was what I was dealing with: It was that kind of muddled interweaving of argument, fact and assumption with any relevant accounting expertise camouflaged to the point of being unfathomable. This is a somewhat different case. The affidavit of Mr Stokoe does not suffer from that kind of admixture of material, and it was in that context that I said what I did, and from a full reading of HG v The Queen [1999] HCA 2 ; 197 CLR 414, though not a commercial case, it can be seen that it was that very kind of context and problem that the Chief Justice was dealing with in the clear language which he used in that case. 36 Heydon JA, in, if I may respectfully say so, a long and careful judgment, examined matters of expert evidence by way of general principle, as well as the particular evidence in the case before him. The most oft-cited paragraph in relation to the matter with which I am dealing is [85]. In the previous paragraph, his Honour had cited relevant passages from HG v The Queen [1999] HCA 2 ; 197 CLR 414 from the judgment of Gleeson CJ, which it is unnecessary to set out. In [85], Heydon JA said the following: In short, if evidence tendered as expert opinion evidence is to be admissible, it must be agreed or demonstrated that there is a field of "specialised knowledge"; 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; the opinion proffered must be "wholly or substantially based on the witness's expert knowledge"; so far as the opinion is based on facts "observed" by the expert, they must be identified and admissibly proved by the expert, and so far as the opinion is based on "assumed" or "accepted" facts, they must be identified and proved in some other way; it must be established that the facts on which the opinion is based form a proper foundation for it; and the opinion of an expert requires demonstration or examination of the scientific or other intellectual basis of the conclusions reached: that is, the expert's evidence must explain how the field of "specialised knowledge" in which the witness is expert by reason of "training, study or experience", and on which the opinion is "wholly or substantially based", applies to the facts assumed or observed so as to produce the opinion propounded. If all these matters are not made explicit, it is not possible to be sure whether the opinion is based wholly or substantially on the expert's specialised knowledge. If the court cannot be sure of that, the evidence is strictly speaking not admissible, and, so far as it is admissible, of diminished weight. And an attempt to make the basis of the opinion explicit may reveal that it is not based on specialised expert knowledge, but, to use Gleeson CJ's characterisation of the evidence in HG v The Queen (at 428 [41],) on "a combination of speculation, inference, personal and second-hand views as to the credibility of the complainant, and a process of reasoning which went well beyond the field of expertise. 42 In BHP Billiton Iron Ore v National Competition Council (2007) 162 FCR 234, the Full Court of this Court once again returned to the issue. At [185] in the reasons of Greenwood J, with which Sundberg J agreed, his Honour dealt with the whole question of expert evidence as follows: The appellants contend on appeal that the evidence of the economic experts is inadmissible as irrelevant. The evidence was admitted on the basis of contextual elaboration of the extrinsic material. The evidence is relevant if it is evidence that if accepted could rationally affect (directly or indirectly) the assessment of the probability of the existence of a fact in issue in the proceeding ( Evidence Act 1995 (Cth), s 55(1)). Evidence of an opinion is not admissible to prove the existence of a fact about the existence of which the opinion was expressed (s 76(1)) although, if a person has specialised knowledge based on the person's training, study or experience, the opinion rule does not apply to evidence of an opinion of that person that is wholly or substantially based on that knowledge (s 79). The normal role of an expert is to give an opinion based on clearly identified facts ( Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305 ; (2001) 52 NSWLR 705), almost invariably assumed to be the facts, on the footing that those facts provide a proper foundation for an opinion within the demonstrated discipline or field of specialised knowledge of the expert witness. Although s 79 of the Evidence Act seems to operate on the footing that the opinion of a person wholly or substantially based on specialised knowledge is not precluded by s 76(1) in the absence of proven foundation facts ( Sydneywide Distributors Pty Ltd v Red Bull Australia Pty Ltd (2002) 55 IPR 354 [10]; Neowarra v Western Australia (No. 1) [2003] FCA 1399 ; (2003) 134 FCR 208), little or no weight will be given to such an opinion ( Ramsay v Watson [1961] HCA 65 ; (1961) 108 CLR 642) although the central point may simply be the question of admissibility, not weight ( HG v R [1999] HCA 2 ; (1999) 197 CLR 414 at [39] [44]; Trade Practices Commission v Arnott's Ltd (No. 5) (1990) 21 FCR 324 at 327-330). That question does not arise here. In this case, the experts did not seek to offer an economic opinion related to disputed or undisputed facts probative of a matter in issue. They sought to offer an historical or contextual explanation as an elaboration of extrinsic material going to Part IIIA of the Act. It is difficult to see how that evidence is truly admissible except perhaps in that unusual category of 'expert non-opinion evidence' descriptive of a relevant element of the economic discipline concerning the evolution of economic concepts of access to natural monopoly infrastructure, without offering any opinion about facts in issue. In any event, the material is capable of being received by the court and considered by force of Order 10, rule 1(2)(j) of the Federal Court Rules , by way of a submission rather than admissible evidence.