MASON A.C.J., WILSON, BRENNAN, DEANE, DAWSON JJ.: This is an appeal as of right from a unanimous decision of the Court of Appeal of the Supreme Court of New South Wales, dismissing an appeal from an award of the Workers' Compensation Commission made in favour of the respondent.

2. The material findings of the Commission, made by Judge Langsworth, may be stated summarily as follows:

(1) On 17 June 1975 the appellant suffered injury in the

course of his employment with the respondent, the injury

being an aggravation of pre-existing pathology in the

lumbar spine with some nerve root irritation. The judge

was not satisfied that he suffered a prolapsed disc

aggravation was other than a temporary one producing

Municipal Council from August 1975 to February 1976 and

thereafter was self-employed more or less consistently

as a bricklaying contractor until December 1978.

bricklaying contract, the appellant suffered a massive

disc prolapse at the L3-4 level when he picked up a bag

of cement. The injury developed a cauda equina lesion

for which he underwent surgery on 15 December 1978. He

has since been seriously incapacitated for work.

(4) The judge was not satisfied that the injury received on

17 June 1975 accelerated the degenerative condition of

the lumbar spine nor that it put the appellant at risk

or added to the risk of the prolapse which occurred on

12 December 1978.

An appeal lies from the Commission to the Court of Appeal only on a question of law or the wrongful admission or rejection of evidence (s.37(4) Workers' Compensation Act 1926 (N.S.W.) as amended). In support of his appeal, the appellant alleged in substance that Judge Langsworth had erred in law in two respects:

(a) that there was no evidence, or insufficient evidence, to

sustain the finding that the probabilities were that in

December 1978 the appellant, while self-employed, had

suffered a fresh injury, causally unrelated to the

original work injury of 17 June 1975, as the result of

lifting a bag of cement;

(b) that his Honour acted on the opinions of expert medical

witnesses, which opinions were based on assumptions and

hypotheses the factual bases for which were not

established by the evidence.

The Court of Appeal concluded that the evidence was sufficient to sustain the findings of the Commission. The appellant now exercises the right which was available to him at the time of the decision of the Court of Appeal to re-litigate those questions in this Court.

3. The first of these matters requires some brief explanation. The appellant denied having suffered any injury in December 1978. He said that while he was on the job on 12 December he got a terrible pain in his back and legs and went to rest in the shed where the cement was stored. There were two bags of cement lying one on top of the other and he pushed one away in order to lie down. He said that the pain was so bad that he screamed for his labourer, Mr Brown, to come and massage his legs. After a time Mr Brown helped him to his car and he left the site.

4. On the other hand Mr Brown, a witness called for the respondent, testified that on the day in question the appellant went into the shed to get a bag of cement. That would ordinarily be the labourer's job but on this occasion Mr Brown was engaged in preparing a mix. The next thing Mr Brown heard after the appellant entered the shed was him screaming out. He then entered the shed to find the appellant lying on the ground with a bag of cement, which had been taken off the stack, lying close to him. Mr Brown said that the appellant was screaming in agony and actually said to him that he went to pick up a bag of cement. He was not cross-examined on this evidence. He did not say whether there were more than two bags in the stack.

5. Judge Langsworth said that Mr Brown appeared to him to be an honest and reliable witness. There was no attack on his credit. His Honour inferred "from all the evidence before me" that the appellant did pick up a bag of cement. Elsewhere in his reasons for judgment he described the reasonable and probable inference as being that the appellant went into the shed to get a bag of cement and that in the course of lifting or moving the bag off the stack he developed very severe pains and fell to the floor. Apart from the evidence of Mr Brown, there was medical evidence which pointed to the likelihood of some such occurrence having taken place about that time as an explanation of the severe disc protrusion leading to a cauda equina lesion which produced such pain and required such urgent surgical treatment.

(1) that the Commission was not entitled to find that on

12 December 1978 the appellant suffered a fresh injury

causally unrelated to the injury of 17 June 1975;

(2) that the opinions of the medical witnesses relied upon

to support the finding that there was a fresh injury

were based on assumptions which were false; and

(3) that by reason of the falsity of the assumptions, the

opinions were so deprived of evidential value that the

Commission was not entitled to place any weight on them

in making the finding which was made.

7. Our summary of the materials indicates that the evidence of Mr Brown and the appellant, quite apart from the medical evidence, provided a basis for the Commission's finding that there was a fresh injury.

8. The second and third submissions advanced for the appellant are related to the first. The history which the appellant gave to the doctors who examined him from time to time did not include any reference to a trauma experienced on 12 December 1978 precipitating his hospitalization and surgery. The only incidents to which he referred were the original incident of 17 June 1975 and the onset of pain on 11 November 1978 when he engaged in a perfectly ordinary operation of opening a shed door, a door which opened without effort. The written medical reports consequently did not address adequately the history which was revealed in evidence, and this led to the experts being asked to express opinions on the basis of hypotheses. The appellant submits that those opinions were of little or no weight and that the judge should not have acted upon them for the reason that the assumptions put to the witnesses did not correspond to the evidence given by Mr Brown and that there was no other evidence to support them.

9. It is trite law that for an expert medical opinion to be of any value the facts upon which it is based must be proved by admissible evidence (Ramsay v. Watson [1961] HCA 65; (1961) 108 CLR 642). But that does not mean that the facts so proved must correspond with complete precision to the proposition on which the opinion is based. The passages from Wigmore on Evidence cited by Samuels J.A. in the Court of Appeal (Wigmore on Evidence, (1940) 3rd ed., vol.II, 680, p.800; 2 Wigmore, Evidence 680 (Chadbourn rev. 1979), p.942) to the effect that it is a question of fact whether the case supposed is sufficiently like the one under consideration to render the opinion of the expert of any value are in accordance with both principle and common sense.

10. As Wigmore states (at pp.941-942, Chadbourn rev.), "the failure which justifies rejection must be a failure in some one or more important data, not merely in a trifling respect". We are of the opinion, in the light of the acceptance by the Commission of Mr Brown's evidence, that the matters to which the appellant's counsel has referred are not of that character. Whether or not the questions so meticulously argued by Mr Gross for the appellant involve questions of law, in our view, the appeal must be dismissed.