The court was asked whether the development of multiple sclerosis had been caused by physical injury sustained in a motor accident. Medical science was not able to demonstrate the connection between the two, and reliance was placed on epidemiological evidence.
Held: The court referred to the case of Davie as affording: ‘[a]uthoritative guidance on the approach which a court should take to expert evidence’ and ‘Perhaps the essential point is that parties who come to court are entitled to the decision of a judicial tribunal. Such a decision may take account of many rather intangible things such as the demeanour of witnesses and the way that they gave their evidence, but, whatever its components may be, such a decision must be reasoned. As Lord Cooper says, an oracular pronouncement will not do.’ The Lord Ordinary required to test the experts’ evidence and, having done so, to use those parts which he accepted and apply them to the facts of the case. If he did not do so it must be inferred that he misdirected himself, and ‘As with judicial or other opinions, what carries weight is the reasoning, not the conclusion.’
Lord Prosser said: ‘I would wish to make two other general observations, before turning to the issues between the parties. First, there was a certain amount of evidence to the effect that certain views on causation were very widely held, or were no longer widely held. If a particular process of reasoning is widely accepted, then that I think may be persuasive for a court. But the fact that a particular view is widely held, without any persuasive explanation as to why it should be so held, and constitute a conclusion, does not appear to me to be a matter to which a court should give significant weight. Rather similarly, the fact that a particular view was or is held by someone of great distinction, whether he is a witness or not, does not seem to me to give any particular weight to his view, if the reasons for his coming to that view are unexplained, or unconvincing. As with judicial or other opinions, what carries weight is the reasoning, not the conclusion.’ and
”In ordinary (non-lawyers’) language, to say that one regards something as ‘probable’ is by no means to say that one regards it as ‘established’ or ‘proved’. Yet in the civil courts, where we say that a pursuer must prove his case on a balance of probabilities, what is held to be probable is treated as ‘proved’. I do not suggest that any lawyer will be confused by this rather special meaning of the word ‘proved’. But speaking very generally, I think that the civil requirement of a pursuer – that he satisfy the court that upon the evidence his case is probably sound – would in ordinary language be regarded as very different from, and less stringent than, a requirement that his case be established or proved. More importantly in the context of such a case as the present, the fact that the two concepts are distinct in ordinary language, but the same in this legal context, seems to me to give rise to a risk of ambiguity or misunderstanding in the expressed opinions of expert witnesses. And this risk will be increased if the expert in question would normally, in the exercise of his profession, adopt an approach to such issues starkly different from that incumbent upon a court. Whether one uses the word ‘scientific’ or not, no hypothesis or proposition would be seen as ‘proved’ or ‘established’ by anyone with any form of medical expertise merely upon the basis that he had come to regard it as probably sound. (Indeed, I think even the word ‘probable’ would be reserved for situations where the likelihood is thought to be much more than marginal). And even if, in relation to any possible proposition or hypothesis, such an expert even troubled to notice that he had come to the point of regarding it as not merely possible but on balance ‘probable’, then I think he would regard that point as one from which he must set off on further inquiry, and by no means as being (as it is in the courts) a point of arrival. Mere marginal probability will not much interest him. But it must satisfy a court.”
Lord Prosser discussed the method of proof: ‘I am not much impressed by one argument advanced for the defender to the effect that the pursuer’s argument is essentially ‘post hoc, ergo propter hoc’, and therefore unsound. Plainly, one will more readily conclude that B is caused by A, or probably caused by A, if one can identify, or at least envisage, some kind of mechanism whereby B might be caused by A. Equally, if one simply cannot identify or envisage such a mechanism, the mere fact that on one occasion B happened after A (and perhaps very quickly after A) would not, in the absence of other indications, lead one easily to conclude that B was caused by A. But no one, certainly in this case, suggests that such a single coincidence is to be interpreted as involving a causal relationship. And once one moves from single coincidence to a number of occasions when B follows (perhaps quickly) upon A, dismissiveness of ‘post hoc, ergo propter hoc’ reasoning seems to me to become less and less appropriate. Indeed, unless and until one can identify or envisage a connecting mechanism, countless conclusions as to causal relationship are reached precisely upon a form of ‘post hoc, ergo propter hoc’ reasoning: if B is observed never to occur except shortly after A, the conclusion may be relatively easy – but if B is observed to occur frequently after A, then even if each sometimes occurs without the other, the frequency with which B occurs after A may nonetheless well justify a more or less firm conclusion that A, in certain circumstances, causes B. I do not regard such conclusions as based on false (or indeed simple) logic. The approach is in my opinion inherent not only in conclusions drawn from one’s general experience or ‘anecdotal evidence’. It is inherent also in much experimental research, and also, as it seems to me, in epidemiology. And while it may always seem somewhat insufficient, until one can find an identifiable possible mechanism, as a basis for claiming that the causal link is proved or established, in either ordinary or scientific terms, that feeling of insufficiency strikes me as much less appropriate if one stops short of such claims and contents oneself with saying that the causal relationship is marginally probable (or is proved or established only as required in civil litigation).’
Lord President (Lord Rodger of Earlsferry), Lord Prosser
1998 SC 548
Cited – Davie v Magistrates of Edinburgh 1953
Issues arose in relation to the expert evidence which had been led.
Held: The court rejected a submission that, where no counter evidence on the science in question had been adduced for the pursuer, the Court was bound to accept the . .
Appeal from – Dingley v Chief Constable of Strathclyde Police HL 11-May-2000
The officer had been injured in an accident in a police van. He developed multiple sclerosis only a short time afterwards. The respondent denied that the accident caused the MS.
Held: There is no proof of what causes MS, but it was common . .
Cited – McTear v Imperial Tobacco Ltd OHCS 31-May-2005
The pursuer sought damages after her husband’s death from lung cancer. She said that the defenders were negligent in having continued to sell him cigarettes knowing that they would cause this.
Held: The action failed. The plaintiff had not . .
Cited – Sienkiewicz v Greif (UK) Ltd; Knowsley Metropolitan Borough Council v Willmore SC 9-Mar-2011
The Court considered appeals where defendants challenged the factual basis of findings that they had contributed to the causes of the claimant’s Mesothelioma, and in particular to what extent a court can satisfactorily base conclusions of fact on . .
Cited – Kennedy v Cordia (Services) Llp SC 10-Feb-2016
The appellant care worker fell in snow when visiting the respondent’s client at home. At issue was the admission and status of expert or skilled evidence.
Held: Mrs Kennedy’s appeal succeeded. ‘There are in our view four considerations which . .
Lists of cited by and citing cases may be incomplete.
Updated: 13 May 2022; Ref: scu.226223