A decision of the Court of Session (Inner House, First Division). Lord President Cooper said,
On the major issue of liability the evidence falls into three chapters:—(i) factual evidence; (ii) expert evidence of an architectural or engineering nature relating to the structural damage and its probable cause; and (iii) scientific opinion evidence on the theory of propagation of ground waves caused by explosives.
The only difficulty experienced by the Lord Ordinary and developed before us arose from the scientific evidence regarding explosives and their effect… The value of such evidence depends upon the authority, experience and qualifications of the expert and above all upon the extent to which- his evidence carries conviction, and not upon the possibility of producing a second person to echo the sentiments of the first, usually by a formal concurrence….
Founding upon the fact that no counter evidence on the science of explosives and their effects was adduced for the pursuer, the defenders went so far as to maintain that we were bound to accept the conclusions of (the expert). This view I must firmly reject as contrary to the principles in accordance with which expert opinion evidence is admitted. Expert witnesses, however skilled or eminent, can give no more than evidence….Their duty is to furnish the Judge or jury with the necessary scientific criteria for testing the accuracy of their conclusions, so as to enable the Judge or jury to form their own independent judgment by the application of these criteria to the facts proved in evidence. The scientific opinion evidence, if intelligible, convincing and tested, becomes a factor (and often an important factor) for consideration along with the whole 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….
Edited for ease of reading. Part of this reasoning was cited in Rogers.
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