The expert evidence
27 The other ground of attack by the applicants upon the primary judge's decision related to the expert evidence on the negligence issue. They contended that no, or no significant, weight should have been given by the judge to the report of Professor Fulde because there is an absence of reasoning in that report.
28 The applicants are correct in saying that there is an absence of reasoning in the report. The report simply contains a conclusion (see [10] above). It does not provide any reasoning that would enable the Court to assess the force of the report and weigh it against the report of Associate Professor Murray.
29 In these circumstances I consider that the primary judge was in error in giving weight to the report. It is apparent from [25] and [26] of his Judgment (see [18] above) that he regarded the report as providing significant evidence in opposition to the case advanced by the applicants and that it was this report which resulted in his Honour being "unable to conclude at the level of comfortable satisfaction that the plaintiff would obtain judgment".
30 As Heydon JA (as his Honour then was) indicated in Makita, for an expert report to be useful it is necessary for it "to comply with a prime duty of experts in giving opinion evidence: to furnish the trier of fact with criteria enabling evaluation of the validity of the expert's conclusions" (at [59]). Heydon JA referred to the observations of Lord President Cooper in Davie v Lord Provost, Magistrates and Councillors of the City of Edinburgh [1953] SC 34 at 39-40 which included the following:
"The scientific opinion evidence, if intelligible, convincing and tested, becomes a factor (and often an important factor) for consideration along with the whole of other evidence in the case, but the decision is for the Judge or jury. In particular the bare ipse dixit of a scientist, however eminent, upon the issue in controversy, will normally carry little weight, for it cannot be tested by cross-examination nor independently appraised, and the parties have invoked the decision of a judicial tribunal and not an oracular pronouncement by an expert" (cited in Makita at [59]).
31 To like effect are the statements, also quoted by Heydon JA, in Makita of Sir Owen Dixon in an extra-judicial address that "[c]ourts cannot be expected to act upon opinions the basis of which is unexplained" (Makita at [60]) and of the authors of Phipson on Evidence, 15th edition (2000) London Sweet & Maxwell, that "[i]n general, an expert may give evidence in chief as to the grounds on which he has reached his opinion, and it may be said that, without the grounds, the opinion is valueless" (Makita at [63]).
32 The application for interim payment required the primary judge to undertake a preliminary assessment, upon the basis of the evidence before him and on the balance of probabilities, of whether, if the proceedings went to trial, the applicants would obtain substantial damages. Such an assessment is in my view to be made upon the basis of the evidence put before the court as to the substantive issues and not on the basis of mere speculation as to what might or might not be the evidentiary position at the final hearing. Thus, it was for the judge here to consider on the negligence issue such of the evidence that was before him as was entitled to weight. The report of Associate Professor Murray was entitled to be given weight but, for the reasons I have given, the report of Professor Fulde was not. The report of Professor Morris in support of the applicants' case was, because of its paucity of reasoning, entitled to little weight.
33 The result is that the only significant evidence on the negligence issue strongly favoured the applicants. In my view, in reconsidering the relevant issue, this Court should be satisfied on the balance of probabilities that "if the proceedings went to trial, the plaintiff would obtain judgment for substantial damages against the defendant".
34 I add in relation to the nature of the assessment to be made that there may be cases in which it is proved that particular, identified evidence not available at the time of the application for interim payment will be available at the trial. In my view, in such circumstances the court would need to take this into account in deciding whether it was satisfied about the relevant matter.