Bushell v Repatriation Commission

REASONS FOR JUDGMENT Factual Background Maxwell William Levier was born on 3 August 1927. He enlisted in the Australian Army on 15 March 1946 and served with the Second Australian Infantry Force until 1 April 1948. After his initial training he was posted to Liverpool in New South Wales from 20 May 1946 to 17 October 1946. There he was trained in bomb disposal and was involved in what he called the "delousing" of twenty five pound shells. Mr Levier was posted with the Occupational Forces in Japan where he arrived on 16 December 1946. He was stationed at Hiro, which is about twelve kilometres from the epicentre of the atomic bomb explosion at Hiroshima. His arrival at Hiro was sixteen months after the blast which occurred in August 1945. While on his posting in Japan he became a bandsman. Mr Levier returned to Sydney on 22 March 1948. He was discharged from the AIF on 1 April 1948. On 3 August 1953 he re-enlisted in the Australian Regular Army and served until his discharge on 15 April 1976. This second period of service was entirely within Australia. He was posted to the Southern Command Band at Albert Park Barracks. After his discharge he taught music at St. Johns College Braybrook from 1976 until 1979. He joined the Victorian Police Band in September 1980. He was discharged from the Police Band on medical grounds in June 1985. He has not worked again since that time. He has been in receipt of a Police Disability Pension and a part invalid pension. In 1986 or 1987 Mr Levier was diagnosed as suffering from chronic lymphatic leukaemia (CLL). On 16 May 1991, he lodged a Veteran's Claim for Disability Pension and Medical Treatment at the Department of Veterans Affairs in Victoria. The claimed disability was chronic lymphatic leukemia. Mr Levier asserted in his application for Disability Pension that his conditions of service had contributed to his disability as follows: "EXPOSURE TO IRRADIATED TERRAIN & WATER SUPPLY CONTRIBUTED TO THE DEVELOPMENT OF CHRONIC LYMPHATIC LEUKAEMIA. SERVED AT ATOMIC BOMB SIGHT (sic) AT HIROSHIMA DURING DECEMBER 1946. WAS STATIONED IN BARRACKS AT HIRO ABOUT 10 KM FROM HIROSHIMA. OUR WATER SUPPLY WAS FROM HIROSHIMA AND LOCAL BEER RATION WAS MADE IN HIROSHIMA." On 1 October 1991 a delegate of the Repatriation Commission wrote to Mr Levier advising that he was unable to accept his claim. On 4 March 1992, Mr Levier applied for review of that decision by the Veterans Review Board. The Board heard the application on 6 October 1992 and adjourned the hearing to obtain a further report through the Secretary of the Department of Veterans Affairs from Professor Salem. The information requested was not provided to the Board until November 1993. It was in the form of a report from Professor Salem dated 8 September 1993. On 10 January 1994, the Veteran's Review Board affirmed the decision of the Repatriation Commission. On 25 March 1994, Mr Levier applied to the Administrative Appeals Tribunal to review the decision of the Veteran's Review Board. Pending the hearing before the Administrative Appeals Tribunal he made a fresh application, on 24 June 1994, for Disability Pension and Medical Treatment. The disabilities he claimed on this occasion were "nervous problems due to stress of overseas services" and "stomach problems caused by anxiety". That application was refused by the Repatriation Commission on 27 October 1994. The application to the Administrative Appeals Tribunal was heard on 26 April 1995 and on 17 October 1995 the Tribunal affirmed the decision under review. On 16 November 1995, Mr Levier lodged an application to this Court for review of the decision of the AAT. That application came on for hearing on 9 May 1997. Statutory Framework The liability of the Commonwealth to pay pensions other than service pensions under the Veterans' Entitlements Act 1986 is set out in sub-s 13(1): "13(1) Where: (a) the death of a veteran was war-caused; or (b) a veteran has become incapacitated by a war-caused injury or a war-caused disease; the Commonwealth is, subject to this Act, liable to pay: . . . (d) in the case of the incapacity of the veteran - pension by way of compensation to the veteran; in accordance with this Act." Section 120 of the Veterans' Entitlement Act 1986 provides, inter alia: "120(1) Where a claim under Part II for a pension in respect of the incapacity from injury or disease of a veteran, or of the death of a veteran, relates to the operational service rendered by the veteran, the Commission shall determine that the injury was a war caused injury, that the disease was a war caused disease or that the death of the veteran was war caused, as the case may be, unless it is satisfied beyond reasonable doubt, that there is no sufficient ground for making that determination. . . (3) In applying sub-section (1) or (2) in respect of the incapacity of a person from injury or disease, or in respect of the death of a person related to service rendered by the person, the Commission shall be satisfied beyond reasonable doubt, that there is no sufficient ground for determining: . . . (b) that the disease was a war caused disease or a defence caused disease; . . . as the case may be, if the Commission, after consideration of the whole of the material before it, is of the opinion that the material before it does not raise a reasonable hypothesis connecting the injury, disease or death with the circumstances of the particular service rendered by the person. (4) Except in making a determination to which sub-section (1) or (2) applies, the Commission shall, in making any determination or decision in respect of a matter arising under this Act or the Regulations, including the assessment or reassessment of the rate of a pension granted under Part II or Part IV, decide the matter to its reasonable satisfaction." The circumstances in which a disease shall be taken to be a war caused disease is set out in s 9 which provides, inter alia: "9(1) Subject to this section, for the purposes of this Act, an injury suffered by a veteran shall be taken to be a war caused injury, or a disease contracted by a veteran shall be taken to be a war caused disease, if - (a) the injury suffered or disease contracted by the veteran resulted from an occurrence that happened while the veteran was rendering operational service; (b) the injury suffered, or disease contracted, by the veteran arose out of or was attributable to, any eligible war service rendered by the veteran;" Evidence before the Tribunal Mr and Mrs Levier gave evidence before the Tribunal. Evidence was also adduced from two medical witnesses, Dr. Hurley, an oncologist and Dr. Parkin, a haematologist. Evidence for the respondent was given by Professor Salem. Mr Levier said that his smoking habit commenced in Australia. He thought it increased when he was involved in bomb disposal work in New South Wales. He said he had not been a smoker before enlisting. In Japan he would have been smoking twenty to thirty cigarettes a day. He and other servicemen were issued with a tin of fifty cigarettes every fortnight. Upon his posting to Japan, he was stationed at Hiro which, he said, was ten to fifteen kilometres from the site of the atomic bomb explosion. A week or two after his arrival he and members of his unit were taken by truck into Hiroshima where they were present for at least "a couple of hours". They visited the ground zero of the atomic explosion where the framework of a dome remained. He subsequently visited Hiroshima while on leave on "one or two occasions". He recalled going on patrol with rifle companies. He was then in the unit's band. They would go on patrol and sleep on groundsheets. He was not sure where this was in Hiroshima. It was "in the scrub and it was around that area". Mr Levier did not purchase local food stuffs. He and other members of his unit were supplied with water and beer brewed locally under allied supervision. Dr. Hurley's evidence came in the form of two written reports of 24 October 1994 and 18 April 1995 respectively, supplemented by his oral testimony. He was not able to point to any evidence directly implicating either irradiation or smoking in the causation of CLL, which is a disorder affecting lymphocyte cells in the bloodstream. He said, however, that it is well established that irradiation causes changes in the chromosomes of lymphocytes at low doses and that such changes could be found in lymphocytes thirty to forty years later. The absence of epidemiological evidence implicating irradiation in an increased incidence of CLL did not preclude the possibility that it does. As to tobacco smoke, Dr Hurley said it had been demonstrated to be a significant factor in causing carcinoma of the lung and, with the passage of time, had been implicated in cancers of other organs. The report of October 1994 concluded: "In summary, Mr Max Levier has been subjected to irradiation and taken up heavy smoking as a consequence of his service in Japan in the BCOF. There is ample evidence of the general carcinogenetic (sic) potential of these agents which could have contributed tothe (sic) development of chronic lymphatic leukaemia that he now has." In his supplementary report which was by way of comment on a report prepared for the respondent by Professor H Salem, Dr Hurley added the observations that CLL is now being diagnosed with increasing frequency which probably reflects better diagnosis rather than a real increase in its incidence. This means there is some uncertainty regarding past statistics. He noted also that the incidence of CLL in Japan was less than 10% of that in "Western countries". The type of lymphatic leukemia in Japan affects T cells whereas in Western countries 95% of CLL relates to B cells. He referred to a paper by R. Larson in which he said there was evidence of an association between smoking and leukaemia. In the course of his evidence in chief, Dr Hurley said that exposure to a residue in Hiroshima could be a factor in Mr Levier's leukaemia today but it would be "very difficult to produce hard evidence one way or the other". He accepted that it would be reasonable to postulate it as an hypothesis. At the end of his cross-examination it was put to Dr Hurley by the Tribunal that what he was saying was: "...radiation and smoking are both dangerous things in regard to cancer and even though no studies are showing a link between either of those and lympathic (sic) cancer, you are not satisfied that there might not in fact be a link." He agreed that that summarised it fully. The haematologist, Dr Parkin, in a handwritten report dated 25 April 1995 considered whether it was possible to raise an hypothesis connecting Mr Levier's war service with the subsequent development of CLL. He agreed with Professor Salem that there was no direct evidence linking CLL and radiation. In fact the carefully documented large scale studies of radiation and incidence of CLL following the atomic bombing of Hiroshima and Nagasaki showed no increase in CLL in Japanese survivors. He considered, however, that it was an important point that lymphocytes can carry genetic changes of radiation exposure for many years. Lymphocytes are the target cells which become malignant in CLL. If a reasonable hypothesis were to be made, evidence of radiation damage to lymphocytes might be relevant. He was not aware of any direct relationship between CLL and smoking that had been documented. However, there was clear evidence of an increased incidence of a variety of leukaemias in smoking. He referred to a paper by Siegel, Smoking and Leukemia: Evaluation of a Causal Hypothesis - published in the American Journal of Epidemiology 138:1 (1993). From the studies reviewed in that paper Dr Parkin observed in his written report: "...we can clearly say that smoking increases the incidence of cancers which we would broadly consider are blood cancers." Dr Parkin's report discussed the nature of CLL which he said was a term applied to a blood disease recognised late in the 19th century when the nature of the involved cell was poorly understood. It is now however apparent that it is a disorder of B lymphocytes. This type of lymphocyte is involved in the production of antibodies. CLL is therefore more closely related to non-Hodgkins lymphoma than acute lymphoma. Non-Hodgkins lymphomas are largely cancers of B lymphocytes like CLL. This should be kept in mind when drawing conclusions about environmental factors and blood cancers. Dr Parkin speculated, although he called it reasonable speculation, that in some way Japanese people are less susceptible to CLL than Westerners. This means either there is some protective mechanism that Japanese enjoy or some particular susceptibility suffered by the Western population. In the end he offered an hypothesis to link Mr Levier's service to the occurrence of CLL in the following terms: "1. The ex member was exposed to radiation risk and commenced smoking in the services. 2. Irradiation increases the risk of many blood cancers. The only large scale study of radiation and CLL involves a population which seems to be protected from CLL viz Japanese. 3. Smoking increases the risk of a variety of blood cancers including non-Hodgkins lymphoma and acute leukaemias. Although smoking has not been directly linked to CLL it would be difficult to say that it might not be a factor. (a) Cancer is the result of accumulating a series of genetic alterations in a cell over many decades. (b) CLL has identifiable genetic changes (c) The series of genetic changes which are required to develop CLL are not known. (d) Smoking obviously contributes to necessary genetic damage in many other cancers including leukaemias and lymphomas 4. US Veterans have an increased incidence of non Hodgkins lymphoma. CLL is a lymphoproliferative disorder which involves the same B lymphocytes which are usually involved in non-Hodgkins lymphoma." In his oral testimony referring to the Siegel paper, Dr Parkin accepted that CLL was not identified specifically as a consequence of smoking in the studies to which he had referred: "I can only say that smoking is a factor in a lot of leukemias which are basically blood cancers and I guess in a general kind of way CLL would be thought to be one of these cancers. So the evidence is fairly indirect but I'm really making the point that one can't discount smoking as a leukemogenic agent. It clearly is." Professor Salem produced a written report dated 24 January 1995 to the Tribunal. Specifically in relation to Mr Levier he considered that his numerous symptoms were not related to CLL and were secondary to underlying anxiety neurosis. At initial presentation there was no evidence of a heavy tumour burden. Although he had CLL it was at a pre-clinical stage. With the passage of time he maintained a steady state in respect of that condition. His symptoms continued unabated but were not clinically related to the leukaemia. On the question of causation generally, Professor Salem said that CLL is the most common form of leukaemia in Western countries. Although other forms of leukaemia are far less frequent it has not been a problem demonstrating an increase in the incidence of those disorders following irradiation. An example is chronic myeloid leukaemia. The failure of epidemiological studies to demonstrate any increase in the incidence of CLL following exposure to radiation, coupled with the fact that it is the most common form of leukaemia in Western society with a male predominance left Professor Salem in no doubt that radiation was not the cause of leukaemia in Mr Levier. The aetiology of the condition is not known. It is unusual in individuals younger than 50. The effect of age on the immune system may be a factor in its causation. Environmental factors have also been suggested based on epidemiological studies but their nature has not been defined. To Professor Salem's knowledge there was no link between smoking and CLL. Professor Salem prepared a further report by way of comment on the report of Dr Parkin. He addressed the hypothetical possibility of a link between CLL and smoking and radiation in the following terms: "I also agree with the various hypotheses put forward to justify the linking of chronic lymphatic leukemia to smoking and radiation. I do however stand by my previous reports in that the various epidemiological studies to date have not revealed a link between chronic lymphatic leukemia and smoking or radiation exposure. I am happy with any hypothesis but if at the end of the day the studies fail to link a disease with a possible causative factor, the scientific fact remains that the hypothesis was put to the test and shown not be a possibility." He added: "Chronic lymphatic leukemia is a common form of leukemia which is observed in smokers and non-smokers with a similar frequency. To suggests (sic) that smoking contributed to the development of the leukemia or caused it, is in my mind a statement with no foundation and not supported by any facts or study. The same applies to radiation exposure. The possibility that the disease is caused by a virus is very likely and suggested by the demonstration of a viral aetiology in animal models of lymphomas and in some human examples of this condition." There were in evidence before the Tribunal some scientific journal articles. Two of them reported studies of the incidence of cancers in US veterans. The first by Namboodiri and Harris published in Cancer 1991; 68 at 1123 assessed haematopoietic and lymphoproliferative cancer risk among 3.7 million US male veterans who used the Veterans Administration medical system. It showed, inter alia, a risk increase for all leukaemias including lymphocyte leukaemia. The researchers noted higher percentages of chronic alcohol abuse and cigarette smoking in this group. However, a definitive understanding of the cause and pathogenesis of haematopoietic and lymphoproliferative cancers remains elusive. Other causative factors hypothesised included radiation hazard. However information relating to exposures to irradiation was not readily available. Another study of US veterans was by McLaughlin and Others in the International Journal of Cancer 1995; 60 at p 190 entitled Smoking and Cancer Mortality Among US Veterans: A 26- Year Follow-Up. The study showed "a continuing excess mortality related to smoking". A number of different cancers were considered and it was observed that: "Our extended analysis indicates that not all cancers are tobacco-related. Little or no differences in risk between smokers and non-smokers were detected for skin and brain cancers, lymphomas and multiple myeloma. Risks of these cancers (except lymphoma) actually tended to decrease with increasing amount smoked." As the Tribunal pointed out, however, this paper focussed on fatal cancers and, given the low mortality of people suffering CLL there would not be many CLL sufferers represented in the study. Professor Salem made the point in relation to this article that leukaemias which may be very different conditions should not all be treated as one category for the purpose of this kind of analysis: "...as far as I am concerned chronic lymphatic leukemia and acute leukemias are different diseases." In Siegel, Smoking and Leukemia: Evaluation of a Causal Hypothesis in the American Journal of Epidemiology 1993; 138 p 1, a number of studies was reviewed and the observation made that: "There appears then to be an elevated risk of leukemia in smokers that is most striking for myeloid leukemia but is not seen for lymphatic leukemia." The conclusion of the article was that "it appears that smoking causes myeloid leukemia". It went on to say: "Since there are insufficient data to rule out the possibility that smoking causes lymphatic leukemia and to separate out the effects of smoking on acute versus chronic myeloid leukemia, future studies should be designed specifically to determine the effects of smoking on cell-specific leukemia risk." Also before the Tribunal was a paper by R A Larson and Others entitled "Acute Leukemia: Biology and Treatment". The authors of that paper stated that it is very difficult to draw conclusions from the literature about the aetiology of leukaemia. They made the point repeatedly made by Professor Salem in his evidence that: "Studies have tended to group together either all leukemia or broad subgroups. We now know that leukemia is a heterogeneous disease and risk factors may be different for specific subtypes." Identified risk factors included ionising radiation at fairly high doses. Other exposures that may increase leukaemia risk were said to include cigarette smoking. The Tribunal's Decision The Tribunal referred to the decision of the High Court in Bushell v Repatriation Commission (1992) 175 CLR 408 and Byrnes v Repatriation Commission (1993) 177 CLR 564. It quoted passages from Bushell about what constitutes a reasonable hypothesis for the purposes of s 120. It identified as its first task the determination of whether the material before it raised a reasonable hypothesis, accepting that an hypothesis could be reasonable although unproven but not if contrary to proved scientific facts for the known phenomena of nature. Nor would it be reasonable if obviously fanciful, impossible, incredible or not tenable or too remote or too tenuous. The Tribunal also gave consideration to the approach to be taken to the evidence of expert medical witnesses in conformity with the decisions of the High Court. It accepted that the case must be rare where it could be said that an hypothesis based on the raised facts is unreasonable when advanced by a medical practitioner who is eminent in the relevant field of knowledge. The Commission (and the Tribunal) was not required to choose between competing hypotheses or to determine whether one medical or scientific opinion was to be preferred to another. It could, however, have regard to medical or scientific material opposed to that which supports the veteran's claim. The Tribunal found that the evidence about Mr Levier's smoking habit was vague and inconclusive as was the evidence about his exposure to radiation. Bearing in mind what had been said by the High Court in Byrnes it proceeded to consider whether a reasonable hypothesis was raised connecting Mr Levier's CLL with his war service if it were to be assumed that he commenced smoking and was exposed to radiation during his operational service. The Tribunal reviewed the medical evidence before it at some length. It noted that the three medical witnesses had all agreed that there were no published studies reporting a positive association between smoking or radiation and CLL. The question was whether the evidence of Drs Hurley and Parkin constituted material raising a reasonable hypothesis of a connection between either or both of smoking and radiation with CLL. Dr Hurley's testimony was characterised by the Tribunal as saying "no more than that radiation and smoking are both dangerous things in regard to cancer and that although no studies show a link between those carcinogens and CLL, he is not satisfied there may not be a link". The hypothesis of connection was supported by Dr Hurley and Dr Parkin but they could not draw on scientific studies which "championed their theory". Nor, in the words of the Tribunal, was there any evidence that any "respectable medical practitioner" other than these two witnesses, accepted the connection between smoking and/or radiation exposure and CLL. The Tribunal said: It seems to us that, while we cannot say that the hypotheses are obviously fanciful, impossible or incredible, or not tenable, they may be said to be too remote or too tenuous because there is nothing pointing to the association, in the sense that there is no scientific basis underlying the hypotheses. The most that can be said for them is, as Dr Parkin said, that "it is possible on the basis of the evidence"." The Tribunal acknowledged that the case must be rare when it is said that an hypothesis based on the raised facts is unreasonable when it is put forward by a medical practitioner who is eminent in the relevant field of knowledge. The Tribunal disposed of Dr Hurley's evidence on the basis, inter alia, that his expertise as an oncologist did not extend to CLL. He had described it in his first report as "an uncommon disease in adults" whereas the other medical witnesses had testified that it was a common disorder. And in his second report he had relied upon the paper by Larson which dealt with acute leukaemia. Both Dr Parkin and Professor Salem had agreed that CLL is a very different disease from acute leukaemia. In his evidence, Dr Hurley had said he had specialised in cancer for thirty five years. When he had begun he dealt with all areas of oncology including lymphoma, leukaemia, cancer and chemotherapy. Now he dealt mainly with carcinomas of the breast, head and neck. He was not cross-examined as to the adequacy or relevance of his expertise. The issues which the Tribunal relied upon to discount his evidence were not raised with him in cross-examination, that is his alleged error in referring to CLL as "an uncommon disease in adults" and his reliance upon the Larson paper. The Tribunal, having decided it could discount Dr Hurley's hypothesis of a connection between CLL and smoking or CLL and radiation as outside his expertise, considered Dr Parkin's evidence. There was no issue here about his expertise. Nevertheless, the Tribunal concluded that although he, like Dr Hurley, had claimed there were reasonable hypotheses of causal connection they were "unsupported by scientific material, were contrary to proved scientific facts, and were too remote or too tenuous to be regarded as reasonable hypotheses". It was critical of his testimony in a number of respects. These included the way in which he characterised the content of the article by Siegel which was said to be "somewhat misleading". The Tribunal was also puzzled by his reliance upon the article by Namboodiri. It also referred to an inconsistency in another part of his evidence. Dr Parkin's hypothesis of a link between irradiation and CLL was seen as relying "on no more than a general belief in the carcinogenic qualities of radiation and smoking". Having concluded that the material before it did not raise a reasonable hypothesis connecting CLL and smoking or irradiation there was no need to refer to s 120(1). the Tribunal was satisfied that CLL was neither a war-caused disease within s 9 of the Veterans' Entitlements Act nor a defence-caused disease within s 120(4). Grounds of Appeal The grounds of appeal as set out on the application and amended (as to paragraph 3(a)) at the hearing are as follows: (a) The Tribunal erred in law in taking into consideration the fact that if the hypothesis raised by Dr Hurley were reasonable then in every case where the veteran who suffered from cancer could claim exposure to radiation no matter where the site or what the studies show about the risk factor for that cancer, the cancer would be found to be a war-caused disease. (b) The Tribunal erred in law in substituting its own interpretation of the scientific studies and rejecting the interpretation given by an eminent haematologist, Dr. Parkin. (c) The Tribunal erred in law in failing to refer to s 120(1) in order to ascertain whether the factors raising the reasonable hypotheses were present in the circumstances of this case. GENERAL PRINCIPLES FOR ASSESSMENT OF LIABILITY By s 120 of the Veterans' Entitlements Act 1986, as interpreted by the High Court in Bushell v Repatriation Commission (1992) 175 CLR 408 at 413-415, the Tribunal is required to determine: 1. Whether the material before it raises a reasonable hypothesis that the relevant injury, disease or death was connected with the service of the veteran - s 120(3). 2. If a reasonable hypothesis is raised whether it is satisfied beyond reasonable doubt that there is no sufficient ground for determining that the relevant injury, disease or death was so connected. The requirement that the material before the Tribunal raise a reasonable hypothesis is satisfied if: 1. The material points to facts which support the hypothesis. 2. The hypothesis can be regarded as reasonable if the facts are true - Bushell (supra) at 414. This means no more than that the material before the Tribunal must raise some fact or facts which give rise to the hypothesis. When the facts have been ascertained, the question for determination is whether the hypothesis is reasonable. It has been said by the High Court in Byrnes v Repatriation Commission (supra) at 570 that facts pointing to the hypothesis may be assumed. In Repatriation Commission v Stares (1996) 66 FCR 594, the Full Court restated the proposition emerging from Byrnes that the hypothesis may assume the occurrence or existence of a fact and that so to do does not make the hypothesis unreasonable. The Full Court did not understand the High Court to be saying that such an assumption is only permissible at the stage of determining whether or not an hypothesis is reasonable. The Court said (at 601): "The question s 120(3) requires to be asked is whether all or some of the facts raised by the material before the decision-maker gave rise to a reasonable hypothesis connecting the veteran's injury with war service: see Byrnes' case at 571. An affirmative answer to that question is not necessarily dependent upon the hypothesis being free from assumptions about a particular fact or facts. Whether the circumstance that a particular fact is assumed leads to the conclusion that the material before the decision-maker does not give rise to a reasonable hypothesis connecting a disease with the circumstances of the particular war service must depend upon all the circumstances of the case in question." In some cases the assumption of facts may be an element of the formation of the hypothesis, the reasonableness of which may be related, inter alia, to the reasonableness of those assumptions. In the present case, as noted earlier, the Tribunal assumed in favour of Mr Levier that he had commenced smoking and was exposed to radiation during his operational service. That assumption was made notwithstanding the vague and inconclusive evidence on both those matters. An hypothesis may be reasonable if the injury or disease suffered by the veteran is commonly associated with the facts raised on the material before the Tribunal. But it may be reasonable even if such an association is not demonstrated or is shown to be uncommon or if scientific or medical opinion supporting the hypothesis has little wider scientific or medical support - Bushell (supra) at 414. An hypothesis will not be reasonable if it is contrary to proved scientific fact or to the known phenomena of nature or is obviously fanciful, impossible, incredible or not tenable or is too remote or too tenuous - Bushell (supra) at 414; East v Repatriation Commission (1987) 16 FCR 517 at 532. A reasonable hypothesis requires more than a possibility - East v Repatriation Commission (supra) at 533. Abstract hypotheses do not fall within the category of reasonable hypotheses contemplated by s 120. As Hill J said in Gilbert v Repatriation Commission (1989) 86 ALR 713 at 719: "The hypothesis must expressly be one which is raised by the material which is before the tribunal. An hypothesis which exists in abstract can not easily be said to have been raised at all by the material before the tribunal. Even if it be a possible interpretation of s 120(3) that an abstract hypothesis is raised merely by the assertion of that hypothesis, such an hypothesis ould not be said to be a reasonable hypothesis of the relationship between the injury, disease or death, on the one hand, and the war service, on the other. A proved scientific fact has been described for the purpose of establishing liability under the Veterans' Entitlements Act as a rule or proposition of universal application which explains or predicts natural phenomena and is accepted by experts within the relevant discipline - Jenkins v Repatriation Commission (1996) 137 ALR 729 at 738. On the question of conflicting medical evidence the joint judgment in Bushell (supra) stated at 415: "Conflict with other medical opinions is not sufficient to reject a hypothesis as unreasonable. As we have earlier pointed out, it is not the function of s 120(3) to require the Commission to choose between competing hypotheses or to determine whether one medical or scientific opinion is to be preferred to another. This does not mean however, that in performing its functions under s 120(3) the Commission cannot have regard to the medical or scientific material which is opposed to the material which supports the veteran's claim. Indeed the Commission is bound to have regard to the opposing material for the purpose of examining the validity of the reasoning which supports the claim that there is a connexion between the incapacity or death and the service of a veteran. But it is vital that the Commission keep in mind that that hypothesis may still be reasonable although it is unproved and opposed to the weight of informed opinion." The function of the Court on appeal from the Tribunal was discussed by Hill J in Horne v Repatriation Commission (Hill J, 8 November 1996, unreported) at p 20: "When the matter comes on appeal to this Court, the Court's powers are limited. The question whether the material before the Tribunal does raise an hypothesis will be a question of fact for the Tribunal to decide. The question whether that material is capable of raising an hypothesis would involve a question of law. The question whether the hypothesis is reasonable is one also for the Tribunal of fact. Indeed, it is one for the opinion of the Tribunal and the Court will not likely interfere with the Tribunal's view. It would only be where the Tribunal has erred in law in forming its opinion that the Court could overrule the opinion." REDUCTIO AD ABSURDUM The first ground of appeal asserts that the Tribunal erred in law in its "reductio ad absurdum" comment on Dr Hurley's evidence. In par 78 of its reasons, the Tribunal said: "If the hypotheses relied on by Dr Hurley were reasonable, then in every case where a veteran who suffered from cancer could claim exposure to radiation or could claim that a smoking habit was linked with the circumstances of service, the cancer, no matter where the site or what the studies show about the risk factor for that cancer, would be found to be a war-caused disease." It was submitted for Mr Levier that that comment reflected the taking into account of an irrelevant consideration on the part of the Tribunal which diverted it from its task of examining the hypothesis pursuant to s 120(1) and (3). The Tribunal, it was submitted, did not make proper inquiry to see whether the hypothesis had been raised in the material provided by Dr Hurley. In so far as that submission suggested that the Tribunal must confine itself to the material presented by Dr Hurley in assessing his hypothesis, it was not correct. The Tribunal is entitled and obliged to consider all the material before it for the purposes of determining whether it gives rise to an hypothesis and whether that hypothesis is reasonable. The significance of the comment quoted from the Tribunal's reasons depends upon how it is characterised. In reviewing the published reasons of the Tribunal it is necessary to consider them as a whole and not to enter upon their analysis with too keen an eye for error in individual passages: "... the reasons of an administrative decision-maker are meant to inform and not to be scrutinised upon over-zealous judicial review by seeking to discern whether some inadequacy may be gleaned from the way in which the reasons are expressed. - Minister for Immigration and Ethnic Affairs v Wu Shan Liang (1996) 136 ALR 481 at 491. The question here is whether the Tribunal was in truth considering the practical consequences of Dr Hurley's hypothesis for other cases. The better view, in my opinion, is that it was doing nothing more than seeking to demonstrate that Dr Hurley's hypothesis was in the category of abstract hypothesis and capable of such wide application to a variety of cases that it could not amount to a reasonable hypothesis in the sense required by the Act. In my opinion, when the reasons of the Tribunal as a whole are considered it cannot be said that this observation, even if capable of the characterisation for which Mr Levier contends has diverted it from its task. THE TRIBUNAL'S REJECTION OF DR PARKIN'S INTERPRETATION The second ground of appeal is that the Tribunal erred in law in substituting its own interpretation of the scientific studies and rejecting the interpretation given by an eminent haematologist, Dr Parkin. It is submitted for Mr Levier that both Dr Parkin and Dr Hurley had provided reports and given evidence of a reasonable hypothesis connecting Mr Levier's service and his condition of chronic lymphoid leukaemia. The Tribunal with no expertise in medicine is said to have rejected the evidence of the two doctors and substituted its assessment particularly in its reasons where it said: "We consider that the hypothesis that smoking may be associated with chronic lymphoid leukemia has been found by the studies referred to in these articles to be contrary to proved scientific facts." In this finding of fact the Tribunal is said to have "usurped the role of Dr Parkin" whom it had recognised as being a highly qualified haematologist. As was said in Bushell (supra) at 414-415 it must be a rare case where an hypothesis based on the raised facts is said to be unreasonable when put forward by a medical practitioner who is eminent in the relevant field of knowledge. As pointed out in the passage cited earlier in discussion of the general principles for the assessment of liability under the Veterans' Entitlements Act 1986 conflict with other medical opinions is not sufficient to require rejection of an hypothesis as unreasonable. But as was also pointed out Bushell this does not preclude the Commission or the Tribunal from having regard to medical or scientific material opposed to that which supports the veteran's claim when performing its functions under s 120(3). There can be no question in this context of the Tribunal "usurping" the role of the expert witness. It is ultimately the Tribunal which has the responsibility for determining whether there is a reasonable hypothesis on the facts raised. That is a matter of fact. While the nature of the test it has to apply has the logical consequence than an hypothesis proposed by an expert in the relevant field , will rarely be rejected as not a reasonable hypothesis the decision and responsibility is that of the Tribunal. To characterise its approach as a usurpation of the role of the expert witness is to reverse the respective functions of the expert witness and the Tribunal in these cases. The Tribunal's evaluation of Dr Parkin's hypothesis involved a finding that on its face the hypothesis relied "on no more than a general belief in the carcinogenic qualities of radiation and smoking". The essential basis of Dr Parkin's opinion was apparent in the following exchange referred to by the Tribunal at par 65: "Is it the nature of your proposition that radiation is dangerous and can cause cancer, but even though the studies do not show a link, there may nevertheless be a link, and that even if there were 100 studies showing it, you could not positively say there was no link? I think that's reasonable. It's not - it would be very difficult to say in a disease which has multiple genetic - requires multiple genetic accidents to produce cancer, that radiation, which is a potent cancer-producing agent, isn't applicable to one or more hits in chronic lymphatic leukaemia. Yes, I think that's a reasonable thing to say." The Tribunal went on to observe that Dr Parkin had hypothesised that exposure to radiation and smoking may each be "a whole series of genetic accidents" required for most cancers. It noted, however, that he acknowledged that no epidemiological evidence pointed to those factors having association with chronic lymphatic leukaemia.