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MEDICO-LEGAL SOCIETY At a meeting of the Society held at the Royal Society of Medicine on Thursday 11 October 1979 the new President was inducted and then gave the Presidential address.

THE EXPERT WITNESS Leonard Caplan Esq QC Dr. Roy Goulding: Ladies and gentlemen, this ends my term of office as President for the past two years and on that same date to which the Hon. Legal Secretary referred - the 14th July, 1979 - the Annual General Meeting unanimously and with acclamation elected as your new President Mr. Leonard Caplan. It is to him, therefore, that we should turn from now on. But before investing him with the Seal of Office, as it were, I would like publicly to express my gratitude to Council and, above all, to the Hon. Officers of the Society for the enormous support that they have given me throughout the past two years. Theirs has been the power without the glory and I thank them very much. It is with enormous pleasure that I invest Mr. Leonard Caplan with the Seal of Office and wish him well in the next two years. I congratulate you, sir. (Applause)

Mr. Leonard Caplan: Fellow members and guests, I find it impossible to believe that any of my predecessors in the office of President of this Society could have been more acutely conscious than I am of the honour and the privilege of having been elected to that position. Our Society, which was founded 78 years ago, was originally concerned only with those aspects of forensic matters which were of common interest to doctors and lawyers. Hence its title, the Medico-Legal Society; hence the fact that we have an Honorary Medical Secretary and an Honorary Legal Secretary; and hence the fact that traditionally when a dinner of the Society is held the two principal toasts proposed are To Medicine and To Law. Over the years, however, a change has come about. The subjects that have been discussed at our meetings and dealt with in our Journal have extended until they now cover a whole range of topics which are of interest to lawyers and all kinds of experts, be they medical or otherwise, whose services are likely to be required in the Courts. It will, therefore, I hope be thought not inappropriate that in this Presidential Address I should be concerned to take a broad view of The Expert in the English Courts. Indeed judging from a report in the Daily Telegraph of Monday the 20th August of this year it is impossible to take too broad, if not too broad-minded, a view of what is expected of forensic experts nowadays. Under the headline "Mini-car rape 'Not possible' ", that report said, and I quote: "After taking 8 years to consider all the possibilities a Court in Turin decided at the week-end that it is impossible for women to be raped in the front seat of a Fiat 500". The report continued, and I quote again: "Experts have proved this beyond doubt', said the ruling, although it fought shy of revealing exactly what tests the experts had carried out in the tiny car" .

125 I would add that it is perhaps regrettable that no information was given in the report as to whether the experts who proved this important truth were doctors or gymnasts, or why it was necessary to experiment over a period of 8 years in order to prove it! Whatever kind of experts they were however, it is certain that as this happened in Italy they were experts appointed by the Court. This highlights a most important distinction between the position occupied by the expert witness in England and other Common Law countries, and his position in most other countries and certainly in Italy, France, Germany, Russia and Austria. It is but rarely in the Common Law countries that one finds an expert witness being appointed by the Court. The nature and reasons for this difference of approach deserve some attention, as do also a number of relatively recent changes which have taken place in this country with regard to expert evidence in civil cases. In the Courts of the Common Law countries the method by which truth is sought is sometimes described as the "adversary" system. This means that every trial, whether civil or criminal, is· regarded as a contest between adversaries, between Plaintiff and Defendant or between Prosecution and Defence. Whatever either adversary seeks to prove or disprove in a trial, he calls appropriate evidence for the purpose of doing so. Where the evidence of one side is in conflict with that of the other, it is the function of the judge, or of a jury where there is one, to decide which evidence is to be preferred. He or they evaluate the evidence, but are in no way responsible for its production or presentation. If the adversaries between them have failed to produce all the evidence which might have been produced, the Court generally must make do with what it has, and in doing so sometimes resorts to the formula that one adversary or the other has failed to discharge the onus of proof which rested upon him. But in civil cases the Court does have an inherent jurisdiction, and in patent cases a statutory power, to appoint its own Court expert to make a report for its assistance when it has difficulty in deciding between conflicting expert evidence. The inherent jurisdiction, however, is very seldom exercised. It is to be observed, though, that a Court expert so appointed is not an expert witness, properly so called, in that he cannot be cross-examined by the parties on his report. An even more rarely used power which exists is that which enables a civil Court to appoint an expert to assist with technical advice in much the same way that nautical assessors are called upon to assist in Admiralty cases. In most other systems of law the methodology is different. The issues with which the Court deals are often not merely those which the opposing sides have chosen to put forward but also those which the Court itself considers relevant. Certainly in criminal cases, and frequently in civil cases, the Court itself actively participates in investigating the truth and where necessary itself procures the evidence of experts. There is much to be said for and against each system: the "adversary" system on the one hand and, what is sometimes called, the "investigative" system, on the other. But it is important to notice that, despite appearance to the contrary, their objectives are not the same. In the latter system it is the absolute truth which the Court is in theory concerned to discover, and to discover, if necessary, for itself; whereas in our system the Court is in theory

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simply concerned to adjudicate upon the strength of such rival contentions as to the truth which the opposing parties have chosen to present to it. Interestingly enough, the history of the development of the law in this country is not without traces. of alternative approaches. In early days a question could arise as to whether a woman was exempt from certain consequences in connection with a trial because she was pregnant, or, as the expression had it "quick with child". When this happened a jury of matrons was empanelled to examine her and report whether it was so. It will be perceived that their duties were akin to those of Court appointed experts, but they were not strictly speaking expert witnesses in that they could not be crossexamined on the opinion they gave. Incidentally it has always seemed to me that "quick with child" was an inappropriate expression, and that "slowed up" might be more apt! Similarly, about 200 years ago when Lord Mansfield was shaping the commercial law of this country he made use of the device of empaneUing what came to be called a City of London Special Jury, consisting of persons who had commercial experience. What he did, however, was to make use of the same people over and over again, so much so that they became known as "Lord Mansfield's jurymen". They, too, were therefore akin to a body of Court appointed experts, although perhaps a more exact analogy would be that of experts appointed by the Court to act as adjudicators, and therefore unlike expert witnesses not subject to cross-examination. Nautical assessors are sometimes appointed to assist the Court in Admiralty cases by giving expert advice upon matters of seamanship and navigation. When this is so, expert evidence tendered by either party is usually inadmissible. Yet here again those nautical assessors, although having a likeness to Court appointed expert witnesses, are not strictly so in that they too are not subject to cross-examination. But, on the other hand, they are not expert adjudicators, in that the Court is not obliged to accept the advice they tender. I can turn now to the expert in his more usual capacity in the Courts as an expert witness, properly so called; that is to say as one who is liable to be required, if his evidence is not agreed, to go into the witness box and be crossexamined. Such an expert witness may be one called by one or other of the parties or, except in the criminal courts, by the Court itself. In criminal cases in this country the Court has itself no power to call an expert witness; although if an expert witness has been called by either the Prosecution or the Defence and has left the witness box, the Court itself may recall him to deal with some point on which it thinks elucidation is required. In the criminal courts an expert witness, therefore, is always a witness for the Prosecution or for the Defence. But in civil cases, although he usually gives his evidence for the Plaintiff or the Defendant, it is possible, though very infrequent, that he is called by neither. This is so because there are provisions by which an expert witness may tender evidence as a witness of neither of the litigants. On the application of a party, but not otherwise, the Court itself may appoint a Court expert to give evidence by way of report. When this happens his remuneration is fixed by the Court and is the joint and several liability of the parties, subject to any order that the Court may make for it to be paid as part of the costs of the action. If, for the purpose of his report a Court expert finds it necessary to carry out an

127 experiment or test, there are provisions dealing with the possibility of the parties being present when it is undertaken. Although such a Court expert may properly be regarded as an expert witness he reports to the Court and to the parties in writing. Any party may then apply to the Court for leave to crossexamine him on his report, and the Court is then obliged to make an order for his cross-examination by all the parties. The report of a Court expert is in no way binding upon the parties nor indeed upon the Court itself. Any part of his report which is not accepted by all the parties is treated simply as information furnished to the Court, to be given such weight as the Court thinks fit. Any party may, on reasonable notice, call an expert witness of his own to give evidence on any question reported on by the Court expert; and in exceptional cases the Court may give a party leave to call more than one expert for this purpose. I have gone in a little detail into these provisions for the appointment of a Court expert because, although they were introduced some 45 years ago, in 1934, it is a matter of interest that they have been little used although available for so long. The reason for this was explained by Lord Denning in a case in 1962 when commenting on the fact that it was said to be a rare thing for a Court expert to be appointed. He is reported as saying: "I suppose that litigants realise that the Court would attach great weight to the report of a Court expert, and are reluctant thus to leave the decision of the case so much in his hands. If his report is against one side, that side will wish to call its own expert to contradict him, and then the other side will wish to call one too. So it would only mean that the parties would call their own experts as well. In the circumstances the parties usually prefer to have the judge decide on the evidence of experts on either side, without resort to a court expert." (Re Saxton, deceased. 1962, 3 All E.R. at p.95.) I now come at last to the expert witness in his most familiar aspect as one who is called by one side or the other to give opinion evidence and be crossexamined upon it. It is quite manifest, of course, that in the complex and highly developed society which has been evolving over the past three centuries many of the disputes which reach the Courts could not be resolved efficiently without the assistance of expert witnesses. Both Bench and Bar are dependent upon that assistance and look for certain qualities in the expert who comes into Court to give it. Many years of practice at the Bar, with occasional stints of deputising as a High Court Judge, have led me to the conclusion that of those qualities there are four that are paramount. They are Expertise, Clarity, Relevancy and Reliability. Stating them in that order is not intended as an indication of their relative importance. As to Expertise, it might be thought that for anyone qualified to be an expert witness it would be a contradiction in terms to say that he lacked expertise, but this is not quite so. A doctor in general practice is qualified technically to give evidence as a medical expert, yet it is perfectly possible that his expertise on some arcane branch of medicine that he goes into the witness box to deal with is so limited as to be almost non-existent. An expert to be of use must be an expert not merely generally in some branch of knowledge, but be an expert specifically in that particular part of it which is in issue before the .Court. Disregard of this can lead to a painful and humiliating exposure of the lack of purported expertise. Many of us remember the classic instance of the

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discomfiture of a supposed engineering expert, called for the defence in the Rouse Murder Case, when liormall Birkett punctured his pretensions in crossexamination by the single sentence: "Tell me, Sir, what is the co-efficient of the expansion of brass?" As to the second quality, Clarity, this is something that the expert witness must always seek through the medium of simple language and simple concept. I emphasise the word "seek", because a special effort is required of him in this connection. He must recognise the necessity of simplifying his language and his thoughts so that an impact may be made upon lay minds. It is desirable that in the witness box he should as far as possible use a different language from that which he would use in discussing the same matter with brother experts. The jargon of science - and I call it jargon only because it sometimes seems so to laymen - is something to be avoided where it can be. Naturally in any specialist field there are some words which have no sufficiently exact equivalent in simple language, and there may be no uncumbersome way of expressing what is meant except by the use of highly technical terms. But it is not always so. And an expert who is detected in using technical terms unnecessarily may even have his credibility affected as a result. I remember an instance of a doctor sending a medical certificate to the Court in support of an application for a three month adjournment of a case on the ground that for medical reasons a litigant would be unable to attend Court during that period. He certified that his patient was suffering from coryza which would incapacitate him for three months. The application collapsed when it transpired that coryza was simply a technical term for what is otherwise known as the common cold. The great American novelist, Herman Melville, author of Moby Dick, once wrote that "a man of true science uses but few hard words, and those only when none other will answer his purpose; whereas the smatterer in science... thinks that by mouthing hard words he understands hard things. " The expert witness should, however, not only use, where possible, the simple language but also the simple concept in order to explain himself. I recollect some years ago being involved in a case concerning the building of a great dam in Africa to ensure the water supply of the city of Nairobi. The contract had been placed with a French construction company, and called for the erection of a gigantic earth barrier across the mouth of a valley in the Kinangop region of the Aberdare Mountains of Kenya. Having obtained the contract and having constructed the lower levels of the dam, the contractors began to raise objections about the stability of the eventual structure. They supported these objections with the opinions of the greatest French experts in the field of soil mechanics. The burden of what they said was that the peculiarities of the local soil made it unsafe for use in building an earth dam. They proved that this soil had an unusually high natural moisture content. It is of course obvious that the higher the moisture content of any particular soil the less stable will be any earth dam constructed from it. This can readily be appreciated if one takes the extreme example of a soil with so high a moisture content that it borders upon being mud. What happens with that soil is that the moisture in it acts as a lubricant between the microscopically minute grains of which all soil is composed. Accordingly it lacks the cohesion requisite for stability when used to build a high earth barrier. The French scientists proved

129 with unassailable evidence that the moisture content of the local soil was so high that the dam would be bound to collapse. They also proved beyond doubt that wherever in the world soil with so high a moisture content had been used for the construction of earth dams the result had always heen an eventual collapse. The city of Nairobi, whose need for water was urgent, decided to obtain the advice of the greatest authority on the subject. He was the renowned Professor Karl Terzaghi, who was in effect the founder of the modern science of soil mechanics, and from whose book "Erd baum mechanik", written in the early 1920s, the very name of that science had come. This wonderful savant, then Professor of Soil Mechanics in the University of Harvard and well over 70 years of age, came to Kenya. Like a mountain goat he clambered allover the part of the earthwork which had so far been constructed and over the surrounding natural slopes. He did not repeat any of the scientific tests which the French scientists had done, nor did he institute any of his own in relation to the shearing resistance, or cohesiveness, of the local soil. After only a few hours on the site, however, he tersely expressed the unequivocal opinion, in his gutteral Austrian accent, that an earth dam made of that soil would stand. How was he able to do so, in the face of all the available scientific evidence? It was done by the simple concept, by common sense, and by a refusal to be blinded by science. The rainy season in Kenya that year had been heavy, and Terzaghi in climbing over the site had seen large pools of rainwater held in by the surrounding soil. Therefore, he said, you can see in practice from these pools that the surrounding soil was capable of holding in the water and therefore possessed the necessary cohesiveness for a dam to be safely constructed from it. All the apparently valid technical scientific reasons to the contrary - and they were weighty indeed - he brushed aside in favour of this simple concept. It may well be asked what was the explanation behind all this which could reconcile the contrary views of distinguished scientists. At the time, none was known. But subsequent improvements in the techniques of electron-ultramicroscopy uncovered the answer. That answer related to the fact that, as I have mentioned, in the ordinary way the moisture content of soil, if high enough, acts as a lubricant between the infinitely minute grains of which all soil is composed, and results in them sliding in relation to each other. The advances in electron-ultra-microscopy revealed subsequently that the soil of the Kinangop included infinitely minute grains which were quite remarkable in structure. They were found to be not solid but to be in the form of tiny hollow tubes sealed at both ends and containing moisture. But this moisture although part of the moisture content of that soil which would be found present on analysis, did not have the usual effect of moisture content. This was because, being encapsulated within grains of the soil, it could not act as a lubricant between grains as it normally would. In the result, although the moisture was undoubtedly present, it might just as well not have been for all the effect it could have on the stability of an earth dam constructed from this soil. I can assure you, however, that when Professor Terzaghi eventually appeared as a witness the part of his evidence which carried most weight was not that concerned with explaining how what the microscope revealed gave the reason why the theoretically dangerous level of moisture content in the local soil had misled the great French scientists. This did not carry half the weight

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given to his account of his having seen the pools of water and the commonsense deduction he had then made. Twenty years later, the great Sasumna Dam in Kenya stands as a monument to the triumph of the simple concept in scientific controversy. Simplicity of concept is the greatest tool in achieving that Clarity which is a pre-requisite of the effective expert witness. Any expert witness who gives his evidence on the basis that his task is to show himself cleverer than his colleagues is absolutely wrong. His task should be to make it seem that the propositions for which he is contending are perfectly clear and obviously correct. Sometimes one hears it said that the opposition had the really clever expert and that our chap only dealt with simple things and had an easy job because the facts were on his side. The truth of the matter is that the clever expert was the one who made it all seem so plain. The next required quality of an expert witness that I have mentioned is that of Relevancy. When there is a failure in this respect it is not always the experts' fault. If part of his evidence is irrelevant it may be due to the fact that he has not been given the advantage of a conference with counsel. In that event it may not be fully apparent to him what are the issues to which counsel will be addressing his arguments, and what is the scientific or technical material that counsel needs for the purpose of those arguments. On the other hand the fault of irrelevancy is sometimes that of the expert witness alone. This will certainly be so if he allows himself to be more concerned with what he believes to be the scientific interest of his evidence rather than its bearing on the matters in dispute. It should never be forgotten that, in the ultimate analysis, the Court is not so much interested in the novelty or even the ingenuity of a scientific theory as in its helpfulness in regard to the decision that has to be made. It may even happen sometimes that the responsibility for the shortcomings of what is presented to the Court by way of expert evidence is the fault of the lawyer and the expert jointly. This occurs when there is a cross-breeding of fallacious ideas between them, so that they both get carried away by something that is "too clever by half". It may well be that this is the explanation of the fascinating case which was heard in the United States of America, in the Courts of California. The facts which gave rise to the case were prosaic. An elderly woman was knocked down and robbed in an alley. All she could remember was that her assailant was a young woman with blond hair. But somebody else saw a white women run from the mouth of the alley way but only saw enough to be able to describe her as young and with blond hair tied in a pigtail. This witness saw the young woman jump into motor car parked nearby, which was then driven off; and she was able to add that the motor car had yellow body work and was being driven by a negro who had a beard and a moustache. Several days later a woman and a man were arrested. She was young, blond and her hair was tied in a ponytail. He was black and had a beard and a moustache. When arrested they were in a motor car with yellow body work. The woman was put on trial. The factual evidence for the prosecution was no more and no less than I have stated. Neither the victim nor the witness was able to make a positive identification of the woman or of the man. The prosecution tendered opinion evidence of an unusual character. They called as an expert witness a college mathematics instructor. For the purpose of his evidence certain statistics were put to him by the Prosecutor. They were

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that in California 1 motor car in 10 had yellow body work, 1 woman in 3 was blond, 1 woman in 10 tied her hair in a pony tail, 1 negro in 4 had a moustache and 1 in 4 had a beard, and finally that the incidence of an inter-racial couple in a motor car was 1 in 1000. On the basis of these statistics the expert said that there was only 1 chance in 12,000,000 that a blond woman with hair in a pony tail would be in a yellow motor car with a negro wearing a moustache and a beard. It was the contention, therefore, of the Prosecution that the combination of all these factors connected with the young woman who robbed the old lady was so astronomically rare that when the same combination was found occurring again a few days later in relation to the woman who was arrested, this proved beyond reasonable doubt that she was the same woman as the one who had committed the offence. The jury returned a verdict of guilty, but on appeal the conviction was quashed. The judgment of the Court of Appeal (People of California -v-Collins 66 Cal. Rptr. 497) said, in effect, that no weight could be given to the expert evidence and that common-sense showed that in any event it would have been no proof of what it set out to prove. Two lessons emerge from the judgment in regard to the use of statistics in expert evidence. The first arises from the Courts' ruling that no weight whatsoever could be given to the experts' evidence based, as it was, upon certain prevalences relating to such matters as blondes with pony tails, negroes with beards, and so on. This was because they had not been proved, but were merely put to him as the assumptions on which he should make his calculations as a mathematician. This defect was not cured by the Prosecutor having invited the jury to take the view that the stated prevalences accorded with their own experience, or to use their own experience as to what the various prevalences were. The expert witnesss's testimony, therefore, was fatally flawed. As the Court said in its judgment: "Mathematical odds are not admissible in evidence to identify a defendant in criminal proceedings so long as the odds are based on estimates the validity of which has not been demonstrated." I would only add that there are circumstances in which an expert can support his evidence by matters which have not been properly proved. He may rely upon the published works of other experts, but only if they are experts in his own field. A medical expert may rely upon the published works of other doctors, but not on published works relating to hydraulic engineering. Any matter concerning hydraulic engineering would have to be proved by an hydraulic engineer. The second lesson to be learned from the case is the manner in which common sense and the simple concept may expose the fallacy underlying the whole evidence of an expert. Even if there had been proper proof that the various proportions were as stated, and it had therefore been properly proved that the factors connected with the woman who committed the crime gave only 1 chance in 12,000,000 of them occurring together, and that same rare 1 chance in 12,000,000 applied to the factors connected with the woman who was arrested, yet this still went nowhere near proving that the two women were the same. There was a missing factor for the purpose of determining the probability of whether they were the same. That missing factor would be the

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size of the population with which one was concerned. For example, if the adult population of California was 24,000,000 then there would be an even chance that there were two women with the same associated characteristics. Therefore the probability against another woman having those associated characteristics would be merely I in 2, not I in 12,000,000. An even chance that the woman who committed the crime and the woman who was arrested were the same person, falls very far short of proving without reasonable doubt that they were. I would not find it surprising if the idea of using statistics as a means of proving identity in that case was the result of a meeting of minds between the Prosecutor and the college teacher of mathematics. The fourth necessary quality for an expert witness to possess is that of Reliability. In this connection I may perhaps be permitted to utter a word of warning about the unconscious bias that may creep into an experts' evidence. Without any reflection upon his integrity, he may feel or find himself being made to feel a member of a team whose object is to win. Respectfully I must stress how important it is to be on one's guard against this. A similar point was put, but in an unjustifiably extreme form, by Lord Jessel, then Master of the Rolls when he said: "in matters of opinion, I very much distrust expert evidence, for several reasons. In the first place, although the evidence is given on oath, in point of fact the person knows that he cannot be indicted for perjury; because it is only evidence as to a matter of opinion. But that is not all. Expert evidence of this kind is evidence of persons who sometimes live by their business, but in all cases are remunerated for their evidence. Now it is natural that his mind, however honest he may be, should be biassed in favour of the persons employing him, and accordingly we do find such bias". (Abinger -v- Ashton L.R. 17 Equity). That language of Lord Jessel seems to me unduly severe. But in my own experience I have sometimes seen another source of unconscious bias which is of more subtle origin. It is very provoking, I am sure, for an expert to be cross examined by somebody who clearly knows little about the subject but nevertheless puts on an air of authority or, even, of offensive scepticism. I can quite understand how an expert may rather lose his balance under certain kinds of cross-examination, particularly if he is inexperienced in giving evidence. The trap, however, is one to be sedulously avoided. It is important for an expert witness to remember that under cross-examination the shorter the answer he gives the better it is likely to be, and the calmer he keeps, the more weighty his evidence will seem. The subject of how the expert should behave under cross-examination leads naturally to the related topic of how counsel should approach the task of cross-examining the expert. However diligent counsel may have been in mastering the technical instructions he has received, and in informing himself from authoritative text books, I am convinced that it is a mistake for him to adopt the pose of being himself an expert. I think that his attitude should be that of subjecting the evidence to the test of logic and commonsense, rather than of opposing it head on with a display of scientific knowledge which has no depth. It is by an oblique attack that he should make his thrust so as to test the evidence at its fundamentals.

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There are various ways in which this can be done. A few of these I should like to indicate in a somewhat light-hearted fashion by assuming that the words of a limerick I am about to quote represented the evidence of an expert. This limerick, which I assure you will not bring a blush to even the most modest cheek, goes as follows: There was a young lady of Ryde Who ate some green apples and died Inside the lamented The apples fermented And made cider inside 'er inside. Now if that rhyme had represented the evidence of an expert witness, let us consider how a cross-examiner might have gone about his job. To begin with it could be suggested that the witness was guilty of using imprecise language in describing the lady as "young". In these days that description when applied to the female sex covers a very wide category indeed. It ranges from sweet sixteen to double that age, which might be called sugary thirty two. Then the witness having described the deceased as a lady might be asked whether he held himself out as an expert in the matter of what is a lady, what were his expert qualifications entitling him to express an opinion whether a woman was a lady or not, and what experience he had in this delicate differentiation. Had he perhaps obtained it in the same way as a famous music-hall comic who used to sing a song with the refrain: 'She's no lady, and only me knows why" . The statement that the young lady came from Ryde brings into focus another matter upon which it is sometimes fruitful to cross-examine an expert, and that is the context in which any of his statements have been made. If, here in England, one speaks of Ryde, it would be understood as a reference to the town on the Isle of Wight. But in Australia it would be understood to refer to the town of that name which is situated near Sidney in New South Wales. As an illustration of how important context may be, one may imagine a situation where there has been a street accident in which someone has been seriously injured. A young and inexperienced doctor who happens to be present is obliged to perform an emergency operation on the spot. Later he is sued for doing it negligently. If some surgeon is called to support the Plaintiff's case, he could and should be cross-examined along the lines that there is no absolute standard of skill and care which a medical man must display, that it differs according to the circumstances, and that what can reasonably be expected in the context of a young and inexperienced doctor who is suddenly called upon to perform a curb-side operation is radically different from what can be expected of a great surgeon operating in a well equipped theatre. So if an expert witness gives opinions about skill and care, or indeed about almost any topic, it may be necessary in cross-examination to probe the context in reference to which his opinions are expressed. Now back again to our limerick, according to the second line of which the person concerned "ate some green apples and died". If that were the expert's evidence it would be pertinent to enquire of him, assuming that he had not been present, how he knew from his own knowledge and not from hearsay that the apples were indeed green. If the expert had formed some opinion of the hypothesis that they were green, their greenness would have to be properly

134 proved. Another instance, from my own practice, occurred in the well-known case of Halsey v. Esso Petroleum Company. In that case the mighty Esso Company was sued by the modern equivalent of the village Hampden. Mr.Halsey lived in a tiny dwelling house near to an Esso Petroleum depot. He complained that he was being subjected to a number of nuisances for which he claimed Esso was responsible. Among these were the emission of polluting chemicals into the air. For the purpose of the Plaintiff's case some experiments were undertaken to establish the rate at which during dry periods particular chemicals were being deposited out of the air in the locality. The experiments consisted of leaving bowls out of doors at a number of points and analysing their contents. Local residents were given the bowls with instructions that they were to keep them out when the weather was dry, bring them in when it was wet, and to keep a note of the length of time that they were out each day. From this data the rate of deposit of various chemicals from the air could be worked out. The bowls in due course were collected from the local residents and a note was made by the expert of how long each bowl had been kept out. When in the course of the Plaintiff's case the expert sought to prove from this material what the rate of deposit had been, he was met with the valid contention that he could not give evidence based upon how long each bowl had been left out, because he did not know this of his own knowledge, but only from what he had been told, and this was mere hearsay. The residents themselves could have given evidence, of course, but by this time they had destroyed their own notes and had no independent recollection of the relevant times. All this points to the moral of asking what is the evidence that the apples were in fact green. With the proposition that the young lady ate some green apples "and died", we come to the vital weapon in the cross-examiner's armoury, namely logic. The young lady may have eaten some green apples and subsequently died, but do these two facts by themselves justify an expert witness saying that she died because she ate those applies? Counsel should always be on the look-out for the logical fallacy of post hoc, propter hoc, after this and therefor because of this. A rise in the national consumption of sugar by 20% over a five year period and a fall in the birth-rate by 20010 in the next five year period, affords no proof that the latter was caused by the former. This is so obvious as to need no embellishment. But it is surprising how often that form of fallacious reasoning seems valid when the circumstances are less obvious. It is probably the most persuasive of all forms of fallacious reasoning. If an angler who has had no luck on a stretch of river for half a day, changes his bait and hooks a fish straightaway, it will be difficult to convince him, however intelligent he may be, that this is no proof that the change of bait was the cause of his change of luck. Cross-examining counsel does well to be always on the look-out for the kind of reasoning that is specious while being superficially attractive. "Inside the lamented", says the next line of the limerick. This brings us into the realm of psychiatry. Was she really lamented? Was lamentation really the feeling of those she left behind, or were their lamentations insincere? This raises a question which not infrequently has to be considered in dealing with the evidence of a psychiatrist. It is often the case that, of necessity, he has to base his opinion to a large extent on the utterances of the person he is examining; and the question is whether these give any firm foundation for expressing a psychiatric opinion. What the person being examined says on a given matter is always subject to three variables. Firstly, it may be true.

135 Secondly, it may be untrue, but he believes it to be true. And thirdly, it may be untrue, and he knows it to be untrue. If, therefore, the formation of the psychiatrist's opinion depends to any extent upon his inter-relating various statements by the person concerned as to his past life or circumstances, the opinion so formed is vulnerable to attack by the cross-examiner. Such an opinion might be compared to a measurement taken by a tape measure made of elastic; elements of variability would vitiate both the opinion and the measurement. We come next to the piece of scientific evidence that "the apples fermented". This is, of course, pure organic chemistry, and is just the sort of thing that cross-examining counsel should avoid, if it is possible for him to do so. Theories of fermentation, whether it was technically an "organised fermentation" or whether it was produced by a chemical agent, are matters which cross-examining counsel should not get involved with, unless he has no alternative. Otherwise he may find himself needlessly groping in a cloud of enzymes. And lastly there is the statement that the apples "made cider inside 'er inside". It has been known for expert witnesses to go too far, and to put their assertions too high. If they do, they expose a flank to the cross-examiner. Could what had been made inside the young lady's inside really pass as cider, and would the expert witness be happy to have it sold to him as such, or wasn't he perhaps being guilty of exaggeration in his evidence? I pass now from these light-hearted hints on how to cross-examine an expert, and come finally to some fairly recent improvements which have been introduced into our system of dealing with expert evidence in civil cases. So long as the adversary system and not the investigatory system operates in our Courts, it is clear that the opposing parties must have the right to call their own experts. One disadvantage of this used to be that, with neither side having to disclose to the other what its expert evidence would be, the opposing experts might well be fighting a blind-folded pillow fight. Another was that counsel, with no advance knowledge of what the other side's expert was going to say, would have to conduct his cross-examination with ammunition hastily passed to him by his own expert. In justification of the way the system used to operate Lord Lindley said, 85 years ago, that "In England it is considered contrary to the interests of justice to compel a litigant to disclose to his opponent before trial the evidence to be adduced against him. It is considered that so to do would give undue advantages for cross-examination and lead to endless side issues; and would enable witnesses to be tampered with, and give unfair advantage to the unscrupulous. It is very true that an honest and fair dealing litigant, on seeing how strong a case his opponent had, might at once withdraw from further litigation. But our rules of evidence and of discovery are not based on the theory that it is advantageous for one side to know what the other can prove, but rather the reverse" (In re Strachan L.R. 1895 Ch at page 445). In the last 25 years or so, these ideas have radically changed, largely because of the pressures resulting from the growth in the number of accident cases heard by the Courts. One effect of this was that in many instances where personal injuries were involved the parties voluntarily exchanged medical reports, although there was no legal obligation upon them to do so. Experience had shown that this often facilitated an agreement between the parties on the

136 quantum of damage, thereby saving costs. In 1969 the Committee on Personal Injuries Litigation made its Report, followed in 1970 by the Report of the Law Reform Committee on Evidence of Opinion and Expert Evidence, and these were followed by the Civil Evidence Act 1972 which introduced very substantial changes that came into effect in 1974. In the High Court now, no oral expert evidence may be called, except with leave of the Court or where all parties agree. Upon an application for such leave the Court may direct that the substance of any expert evidence which it intended to be presented shall be communicated in writing to the other parties to the action, but the Court must first be satisfied that it is desirable to do so. In regard to medical evidence in actions for personal injury it is provided that the full medical reports and not merely the substance shall be given to the other parties unless the Court considers that there is sufficient reason for this not to be done. Among the circumstances which the Court may, if it thinks fit, treat as sufficient reason for not ordering medical reports to be disclosed are that the case involves an allegation of negligence in the course of medical treatment, or that the expert medical evidence may contain an expression of opinion as to how the injury was sustained or as to the genuineness of the symptoms of which complaint is made. These matters bring me conveniently, by the way of conclusion to an experience I once had when cross-examining the great neurologist Sir Russell Brain, later Lord Brain, with the advantage of having seen a copy of his report beforehand. I was appearing for a Plaintiff who had sustained an industrial injury. Sir Russell's report was to the effect that the injury was less severe than alleged. I did my homework and discovered that there was a passage in his book - which was in flat contradiction of a section of his report. Armed with this I led him to make it clear that it meant exactly what it said, with no scope for equivocation. Having stopped up the bolt-holes in this way, I then sprung the trap. Inviting his attention to the passage in his book I asked him, triumphantly, whether it was not diametrically at variance with the evidence he had just been giving. Without a moment's pause, and looking me straight in the eye, Sir Russell said: "Yes, Mr. Caplan, it is; and it is being corrected in the next edition".

DISCUSSION The Hon. Legal Secretary: Ladies and gentlemen. by tradition, no discussion takes place on the Presidential address but I will call upon the Hon. Mrs. Justice Elizabeth Butler-Sloss who will express our very great thanks to our newly elected President for his paper. The Hon, Mrs. Justice Elizabeth Butler-Sloss: Mr. President, ladies and gentlemen, it is a great honour and, indeed, a great pleasure for me on behalf of the Society to express the thanks of the Society and their guests for your speech this evening. I am particularly happy to do so, having known you for so many years. May I say at once that we have been very fortunate tonight to have heard in a very witty and entertaining way a most interesting and scholarly exposition on a subject which I would have thought was very near to the hearts as well as to the conscience of a large number of people who are in this Society. Indeed, it was almost as if Daniel had come to the den of lions, except that our President knows all too well those members who themselves are experts and whom he has met on many occasions in the past. It is not only of great interest to all of us to hear somebody of his experience and his own expertise in the Courts in many different sorts of cases as to how he sees the role of the expert and

137 how he sees what the expert can provide to the Courts; equally, I thought it of great assistance for him to say what are indeed the duties of counsel in coping with the expert. I thought that we were particularly fortunate that it should be done in so entertaining a way. I might perhaps add, as a footnote, that in a particular branch of the profession in which I am involved the Court does in fact frequently get involved with calling its own expert of rather an unusual kind, perhaps - the Court Welfare Officer. That is of a specialist kind, but it does not, in this rather unusual situation, require either counsel to need it, although normally they do approve of it. It seems to me that this evening, with the very interesting, scholarly and entertaining speech that we have had, augurs well for this Society for the next two years and I, for one, look forward with great interest and with a great deal of pleasure to the wit, tact, charm and kindness with which our President will deal with the succeeding speakers over the next two years. (Applause) The President: I am strictly enjoined that I must not say how grateful I am for what has just been said, so of course I will not say it. But I am told that I must make the important and interesting - possibly, for all I know, witty - announcement that coffee is served.