The trial was heard in the High Court by His Honour Judge Eifion Roberts Q.C. He heard evidence over a period of 10 days from a substantial number of expert and lay witnesses. Much of the medical evidence was directed to the question whether the condition was PDA4 and, if so, whether it was organic in origin. The medical issues were controversial, as the condition is such a mysterious one. There is a strong body of medical opinion to the effect that it is an organic condition, due to some kind of trauma or physical injury. There is another strong body of medical opinion that the basis of it is psychogenic, as the product of a somatisation--that it is all in the mind, in layman's terms. It was admitted that the condition is rare in typists. The appellants said that it had never occurred among typists on their premises. The ergonomic experts on each side were agreed that repetitive movements alone were unlikely to cause injury. And no pathology for the condition has yet been demonstrated. So the medical experts differed as to the basis of the condition generally and as to the cause of it in the respondent's case in particular. Much of the evidence from the lay witnesses was directed to the work which the respondent was doing in the performance of her duties as a secretary. The amount of the typing in comparison with her other duties was an important issue, especially in regard to the opportunity which this gave for natural breaks in her typing work.

      The judge held, after analysing the evidence, that the respondent had failed to establish that she was entitled to damages. In the course of a long and careful judgment he said that the most that he could find on the whole of the medical evidence was that the condition of cramp of the hand due to repetitive movements (PDA4) might have an organic cause or a psychogenic cause, or a combination of both causes or one cause to begin with and the other supervening. He was disposed to hold that the respondent had a cramp of the hand, but she had failed to satisfy him that its cause was an organic one. She had also failed to satisfy him that it was caused by her typing work, as opposed to being merely associated with it.

      He then asked himself whether it was reasonably foreseeable that a secretary who was typing to the extent which he had found established by the evidence would be likely to suffer from PDA4. He held that, while this was theoretically possible, it was not reasonably foreseeable. As for the breaches of duty which had been alleged, he did not think that it was incumbent on the appellants to specify rest pauses during the respondent's typing work. This was because she had ample scope to interpose her typing with her non-typing secretarial work. The work lent itself naturally to rotation and interspersment. It could reasonably have been expected that a person of her intelligence and experience would break it up without being told. He rejected the allegation that a warning should have been given of the risk of contracting PDA4. It was not the practice in the industry to give such a warning. This could be counterproductive, because it might precipitate the condition which it was intended to avoid.

      It will be clear from this summary that the issues which the judge had to decide were all issues of fact. The answers which he gave to them were the result of his assessment of all the evidence, after seeing and hearing all the witnesses. He had to resolve an acute conflict in the expert medical evidence. Another disputed question which he had to resolve was what to make of the respondent's evidence. This was important because of the account which she gave as to the development of her condition and as to the nature and amount of her typing work. His impression of her was that she was a dutiful, conscientious and responsible person, and it had not been suggested that she was malingering. But he thought that in her evidence she was at times prone to exaggeration and some inconsistency, although she was not trying to deliberately mislead the court. In this situation he had to examine her evidence on these matters very carefully. He had to test it against the evidence of the other witnesses whose evidence seemed to him to be reliable.

      The respondent appealed against the order made by the trial judge. The Court of Appeal allowed her appeal, but this was a decision by a majority. Stuart-Smith L.J. and Waite L.J. were satisfied that there were sufficient deficiencies in the judgment to justify their intervention on the facts. Having examined the evidence, they reversed his findings on causation, foreseeability and negligence. Swinton Thomas L.J. dissented. He said that he did not believe that it was open to the court to reverse the various findings of fact made by the judge who had had the advantage of seeing and hearing the witnesses.

      I have come to the view, with the greatest of respect to the very experienced judges who constituted the majority, that the Court of Appeal ought not to have disturbed the findings which were made by the trial judge. I am unable to accept the criticisms which were made of his judgment by the majority. It seems to me that he came to a decision on all the main issues which he was fully entitled to reach on the evidence. I have also found it hard to reconcile some of the criticisms of the judgment which were made by the majority with the state of the evidence. This has tended to strengthen my view that the trial judge reached a decision which he was entitled to reach and that it ought not to have been reversed on appeal.

      It will be necessary for me to examine in some detail the reasons which the majority gave for reversing the trial judge. It was to these reasons that Mr. Hytner Q.C. directed the main part of his argument. He said that the Court of Appeal had been wrong to reverse the trial judge both as to where the burden of proof lay in this case and also on various primary findings of fact by the trial judge which went to the root of the issues of causation, foreseeability and negligence. Mr. Redfern Q.C., in seeking to support the decision of the majority, maintained that the decision by the trial judge was vitiated by errors which he had made, especially with regard to the medical evidence. I shall deal with these arguments stage by stage as I examine the state of the evidence.

The Medical Issues

      The judge described the three issues which fall under this heading in this way: firstly, whether PDA4, cramp of the hand due to repetitive movements, has an organic cause; secondly, whether the respondent has had PDA4; and thirdly, if she has had it, whether her PDA4 has an organic cause. I have placed them all under the heading of medical issues. But it is clear from his judgment that the judge was unable to resolve all of them without taking account of a substantial body of evidence from the lay witnesses about the work which the respondent was doing during the critical period.

      As to the first issue, the judge said that the most that he could find on the whole of the medical evidence was that the condition of cramp of the hand due to repetitive movements may have an organic cause or a psychogenic cause or a combination of both causes, and that this was a matter for the court to consider on the evidence before it in each case. In the Court of Appeal Stuart-Smith L.J. described this conclusion as entirely unexceptional. But he then went on to make some comments about the state of the controversy which reveal that his approach to it was very different from the position of neutrality which the judge had decided to adopt at this stage in his examination of the evidence.

      The judge's conclusion was, as Stuart-Smith L.J. noted, in accordance with the evidence of the respondent's witnesses Mr. Stanley, an orthopaedic surgeon, and Dr. Hay, a psychiatrist. The appellants' witness Dr. Lucire, who was also a psychiatrist, said in her evidence that she had found that, where an organic cause was present, it was not related to repetitive movements but to some other organic disorder such as gout. Her explanation for the condition was that in her experience it was due invariably to a somatisation syndrome. Stuart-Smith L.J. said that her evidence was that all cases of PDA4 are due to conversion hysteria. But that was to oversimplify the effect of her evidence. It is true that her diagnosis was that, in the respondent's case, the cramp was the product of conversion hysteria--that is to say, that her mind was using her body to escape from a situation at her work which she had found to be objectionable. But her evidence, when speaking about the condition generally, was not so confined. She talked in quite general terms about somatisation and the phenomenon of hysteria. She said that one had to be careful in ascribing either an organic cause or a psychogenic cause. In this respect she agreed with Dr. Hay, although there was an important difference between them as to the proper starting point. Dr. Hay's position was that a diagnosis that there was a psychogenic cause had to be made with great caution, and then only when there was an absence of a physical cause. He said that conversion hysteria was a rare condition and that it was a diagnosis which had frequently been shown to be wrong. But Dr. Lucire's experience was to the contrary.

      As to the state of the controversy, Mr. Stanley was a strong supporter of the organic school. Yet he accepted that it was an impossible task for a judge to decide which school was right and which school was wrong. In the light of his evidence there can be no doubt that the trial judge was right not to attempt to resolve this dispute. He was right also to describe the possible causes on either side in quite general terms within which a range of diagnoses might be acceptable. But it seems to me that Stuart-Smith L.J. was unwilling to accept that the question as to which school was right was still an open one. Having, as I think, over-simplified the effect of Dr. Lucire's evidence, he said that with advances in medical knowledge and improved medical technology the psychogenic approach had to a large extent been discredited. That however was not the judge's view of the medical evidence which was before him in this case. Whatever may have been the case where other conditions have been said wrongly to have had a psychogenic origin, the evidence in this case was that the pathology for PDA4 is uncertain as it has yet to be demonstrated. I do not think that general knowledge about improvements in medical science and technology, which were not the subject of any evidence, provided a sufficient basis for differing from the judge's view that a neutral position had to be adopted in this case as to the present state of the controversy.

      This difference of view between the majority in the Court of Appeal and the judge on this initial question has an important bearing on the way in which, from different starting points, they approached the other issues in the light of the medical evidence. I do not think that I am being unfair to the majority when I say that it seems to me that they were, from the outset, sceptical about the suggestion that the condition was anything other than organic in origin. The judge, on the other hand, was much more circumspect. As to the second issue, he was careful to say that, while he was disposed to find that the respondent had a cramp of the hand, he was not satisfied that it was due to the repetitive movements of typing in the sense that such movements were an effective cause of it. His choice of words was important, because PDA4 has been defined as "cramp of the hand due to repetitive movements." To accept without qualification that her cramp was PDA4 might be taken as resolving the next issue, as to whether there was an organic cause in this case. That, the most controversial medical issue in the case, the judge wished to examine separately. The majority in the Court of Appeal said that the judge had concluded, without saying so, that the respondent had PDA4. They omitted to add the qualification which the judge had made. By implication they were criticising his finding as lacking in clarity. I think that they were wrong to do so, as the judge made it clear that the question whether this was cramp due to repetitive movements was one which, at this stage, was still unresolved. Their difference of view from the judge on this point provides the explanation for the further and more fundamental difference between them about the proper approach to be taken to the third issue.

      The judge said, in regard to the third issue as to the cause of the cramp, that the appellants did not have to satisfy him that the cause was psychogenic: the onus was on the respondent to establish that the cause was organic. Stuart-Smith L.J. said, at [1997] I.C.R 566,574, that this was a misdirection:

 "Having established that she had PDA4 there were two alternative explanations for it advanced by the medical experts one-supported by the evidence of Mr. Stanley and Dr. Hay- was that it was organic; the other-supported by Dr. Lucire-that it was psychogenic being a conversion hysteria. No other hysterical or psychogenic explanation was advanced. It seems to me that what the judge had to do was simply to decide upon the evidence which of these two explanations was the most likely. In the result the judge said that he was not satisfied that it was organic: therefore by inference it must be psychogenic; but he did not accept Dr. Lucire's explanation that it was conversion hysteria."

Waite L.J., at p. 593 was equally critical of the approach which the judge took as to where the onus lay on this issue:

 "That represents, to my mind, a plain misdirection in law. Why should a plaintiff who has established a condition of PDA4, and who has satisfied the court that the only psychogenic condition relied on against her does not apply in her case, be under any duty to prove a negative and demonstrate that her complaint had no psychiatric origin? Given the intricacies of the human mind, and the breadth of emotional range to which everyone is subject from mere stress at one extreme to hysteria at the other, it seems to me to be illogical, as well as unjust, to lay upon an individual complaining of industrial injury the burden, in the absence of any specific psychiatric diagnosis established by his opponent, of proving a non-psychogenic origin for physical symptoms that are accepted to be genuine."

In my opinion the judge was right to insist that it was for the respondent to satisfy him that her cramp had an organic cause. This was the basis of her case that her condition was foreseeable and that, in failing to take precautions against it, the appellants had been negligent. Unless an organic cause for it was established, her claim for damages was without any foundation in the evidence.

      There is no doubt that in most cases the question of onus ceases to be of any importance once all the evidence is out and before the court. But in this case it was not so simple. As Lord Thankerton observed in Watt v. Thomas [1947] A.C. 484, 487 the question of burden of proof as a determining factor does not arise at the end of the case except in so far as the court is ultimately unable to come to a definite conclusion on the evidence, or some part of it, and the question arises as to which party has to suffer from this. From time to time cases arise which are of that exceptional character. They include cases which depend on the assessment of complex and disputed medical evidence, where the court finds itself in difficulty in reaching a decision as to which side of the argument is the more acceptable. I think that this was such a case, and that the judge was justified in reminding himself where the onus lay as he examined the evidence.

      There were two competing explanations for the condition which had been advanced by the medical experts. Neither of them was wholly satisfactory. Mr. Stanley's explanation that the cramp had an organic cause was open to some criticism. He did not see the respondent until more than three years after May 1989, so he could not say whether the symptoms which formed part of his diagnosis were present on that date. He said that he found three manifestations of functional distonia when he saw her in 1993: a significant weakness of grip, poor function of the hands and loss of muscle bulk. But her grip was tested by Mr. Holt, a rheumatologist recommended by the Repetitive Strain Injury Association, in October 1989. He reported that she had a very good grip, and that he was rather doubtful whether her condition was repetitive strain injury. Dr. Williams, another rheumatologist, examined her in October 1992. He found that her grip was scale four on a scale of five, and that this was normal for a person of her build. The judge said that he found the results of these tests difficult to reconcile with the test which Mr. Stanley had carried out, and he noted Mr. Stanley's acceptance that disuse atrophy is common where the hand is not used. He also noted that none of the doctors who had seen the respondent in 1989 and 1990 had seen any spasm or tremor which, although they are not always present, are two of the symptoms of PDA4 described in the guidance notes. As for Dr. Lucire's diagnosis of conversion hysteria, the judge noted that this explanation also was a difficult one to accept in the light of Dr. Hay's evidence.

      The position which the judge reached after reviewing the medical evidence was that he was unable to decide on that evidence alone whether the organic explanation was the more probable. That was why, after saying what he did about onus, he proceeded to examine the other evidence in order to see whether the onus had been satisfied. This included the respondent's evidence, some of which he thought was exaggerated, and the evidence of two ergonomists. They were agreed that repetitive movements were unlikely to cause injury unless accompanied by other factors, none of which were found by the judge to have been present in this case. He also took into account the findings which he had made about the speed, duration and amount of the respondent's typing work after testing her evidence against that of other witnesses for whom she worked during the critical period. It was only after completing this review and making his findings in the light of all this other evidence that he reached his decision that the respondent had failed to satisfy him that her cramp had been caused by the typing work.

      The majority in the Court of Appeal appear to have thought that the whole matter ought to have been disposed of by looking solely at the medical evidence. On their approach it was enough that the judge was unwilling to accept Dr. Lucire's explanation that the respondent's condition was conversion hysteria. That being so, as there was no other explanation, the conclusion was in their view inevitable that this was a condition which was organic in origin. I have already observed that in my opinion they were approaching the matter from the wrong starting point. But their disposal of this issue is open to objection on more fundamental grounds.

      In the first place what they were doing was to invert the onus of proof. The respondent's whole case was that her cramp had an organic cause. It was essential to her success that it was proved to have been caused by repetitive movements while typing. So, according to the ordinary rule, the onus was on her to prove that the cause which she had alleged was the right one. It was open to the appellants to lead evidence in rebuttal to the effect that its cause was a psychogenic one. But they did not have to prove that it was due to a conversion hysteria. Failure to prove this alternative explanation was a factor to be taken into account in the decision as to whether the respondent had established an organic cause, but it was no more than that. It still left open the question, in the light of the wider dispute revealed by the medical evidence, whether an organic cause had been established for the cramp so that it could be said to have been due to the respondent's typing work. It was precisely because he was unable to answer this question in her favour on the medical evidence that the judge turned for such assistance as it might offer to the other evidence.

      In the second place, the judge had the advantage of seeing and hearing all the medical evidence. The majority of the Court of Appeal said that they were well aware of the rules which define the approach which an appellate court should adopt in these circumstances. But they did not apply them as they should have done in the circumstances. As Lord Bridge of Harwich said in Wilsher v. Essex Area Health Authority [1988] A.C. 1074, 1091, the advantage which the trial judge enjoys is not confined to conflicts of primary fact on purely mundane matters between lay witnesses. In this case the medical experts were at odds with each other about complex issues which were particularly difficult to resolve as no pathology for the condition known as PDA4 has yet been demonstrated. They were examined and cross examined on these issues over several days. Their demeanour and the manner which they gave their evidence was before the judge, who saw and heard them while they were in the witness box. All the Court of Appeal had before them was the printed evidence. The view of the judge that he was unable to come to a conclusion about the effect of this evidence without taking into account the evidence of the lay witnesses was entitled to much greater weight than the majority were willing to give to it. For my part, I think that his approach to this matter was entirely justified in the light of the difficult issues which were presented to him by the medical evidence. In the light of the evidence about the nature and duration of the respondent's typing work, I regard the view of the majority that the judge had no alternative but to accept that there was an organic cause for the cramp as a wholly mistaken one. I think that it was due to an incomplete understanding of the effect of the evidence.

      There is one other criticism of the judge's findings with which I must deal before I leave the issues covered by the medical evidence. It relates to the judge's treatment of the respondent's entry in her diary for 23 May 1989. This was the first entry in the diary, which she had been keeping since 1987, in which she mentioned any trouble in her hands. She recorded in this entry that it had started late in the previous year when she noticed by Friday that her hands were tight and sore, and that she had been typing flat out all that summer to keep up with her typing work. The judge said that he had difficulty in accepting her explanation for not mentioning the problem in earlier entries at the time when the pain was afflicting her and for doing so on 23 May 1989 retrospectively. In expressing this view he said that he had regard also to the opportunities which she had had to mention her trouble on other occasions at or about that time. These included occasions when she could have mentioned it both to her G.P. and to Mr. Mason, one of the managers, when she was discussing her work appraisal with him. He had already noted in his judgment that she was at time prone to exaggerate during her evidence and to some inconsistency, although not to the extent of deliberately misleading the court.

      The majority in the Court of Appeal were particularly critical of his assessment of her evidence. They said that his reasons for not accepting her diary entry made no sense. He could only have meant that she had lied about this entry, which was quite inconsistent with his finding that she had not deliberately misled the court. They made much of this point, as it was their view that the judge had not taken proper advantage of the fact that he had seen and heard her while she was giving her evidence. Having rejected his treatment of her evidence, they went on to rely upon her evidence without subjecting it to the same critical analysis as the judge had given to it. But I think that they made too much of the point, and that they misunderstood the nature of the difficulty. There was no reason to think that the diary entry was a lie. There was no suggestion that she had made up the entry deliberately in order to mislead the court. She had made it in her own private diary, to record her own thoughts at the time when she was writing it. The point which concerned the judge was not whether it was a dishonest entry-- was it really to be thought that she would lie to herself? -but rather whether, as an accurate record of the history of her condition, it was reliable. I think that the judge was fully entitled to express his concern on this point, and to insist that before he accepted the entry as a reliable one it should be tested against the rest of the evidence. On this matter also the majority ought to have acknowledged that the judge had the advantage over them of hearing the respondent's explanation while she was giving her evidence. As Swinton Thomas L.J. said in his dissenting judgment, the judge was entitled to come to the conclusion that he did on this issue of fact, and it was quite impossible for a Court of Appeal to substitute its own finding of fact on it.

Causation

      The fourth issue which was identified by the judge was whether the respondent's PDA4 was caused by her work as opposed to being work related. Although she had failed to satisfy him that her cramp had an organic cause, it was still necessary for him to examine this issue in order to decide whether the disease might nevertheless have been caused by the prolonged typing work which the respondent said she had to do while employed by the appellants as a secretary.