ZEEMAN J The respondent made two applications to the Workers Compensation Commissioner. The first application, made on 9 July 1993, is in the following terms:

"I, JOHN SMITH, hereby apply to the Workers Compensation

Commissioner to hear and determine the following:-

I wish to apply for payment of workers compensation weekly

payments from the 26th February 1993 and payment of my

medical and associated expenses by my employer, the

Tasmanian Ambulance Service, in respect of the injury or

disease I suffered arising out of and in the course of my

employment with the Tasmanian Ambulance Service on or about

the 12th April 1992.

This application is made pursuant to Section 42 of the

Workers Compensation Act 1988."

2. The second application, made on 14 April 1994, is in the following terms:

"I, JOHN SMITH, hereby apply to the Workers Compensation

Commissioner to hear and determine the following:-

1 My entitlement to workers compensation weekly payments and

payment of my medical and associated expenses by my

employer, the Tasmanian Ambulance Service, in respect of the

injury or disease I suffered on or about the 27th December

2 My entitlement to bring a claim for compensation in

respect of that injury or disease given my failure to make a

claim within the period prescribed by Section 32 (1) (b) of

the Workers Compensation Act 1988.

This application is made pursuant to Section 42 and Section

38 (3) of the Workers Compensation Act 1988."

3. The applications were heard together and, on 4 August 1994, the Commissioner determined that the respondent was entitled to receive compensation in respect of the injury alleged to have been suffered by him on 27 December 1990 but not otherwise. The learned Commissioner published one set of reasons for the making of his determinations and made a separate order in respect of each application. The order made on the application made on 9 July 1993 was that the application be dismissed. No appeal has been brought against that order. The order made on the other application was as follows:

"After hearing the parties herein I determine that the

worker is to be paid compensation by way of weekly payments

and medical expenses in respect of an injury suffered on or

about the 27th December, 1990, and I order that the employer

pay the worker the said compensation within 28 days of the

date of this order."

4. The appellant has appealed against that order and the determination leading to it. Although the question is not raised by any ground of appeal, I observe that the order is deficient. Whilst it orders that the appellant pay compensation within 28 days it does not indicate what it is that the appellant is to pay. The Workers Compensation Act 1988 ("the Act"), s61(6) provides that an order of the Commissioner in relation to the payment of a sum of money is deemed to be a judgment of the relevant court of requests and enforceable in that court as provided by the Local Courts Act 1896. It would be impossible to enforce the order made by the learned Commissioner in the way contemplated by s61(6). It is a necessary implication to be drawn from s61(6) that the Commissioner may not make an order requiring the payment of money unless the order specifies some particular sum which is to be paid.

5. The material before the learned Commissioner was such that it did not enable him to make any order requiring the payment of money. The reasons expressed by the learned Commissioner make it clear that he thought that the respondent was entitled to a weekly payment in respect of two periods although he made no precise findings as to what those periods were. There was no evidence before him as to the relevant weekly compensation rate which applied at any relevant time. Insofar as the learned Commissioner made an order concerning medical expenses there was no evidence before him that any had been incurred, quite apart from the quantum thereof or of the facts required to be established to bring them within the Act, s75(1). Despite the defects in the order it is appropriate to consider the grounds of appeal which challenge the determination made by the Commissioner that on 27 December 1990 the respondent suffered an injury within the meaning of s25(1)(b).

6. The notice of appeal contains a large number of other grounds. It is unnecessary to reproduce them. The general effect of the grounds is an assertion that the learned Commissioner erred in law in the following respects:

(a) in concluding that the myocardial infarction admittedly

suffered by the respondent on 27 December 1990 (which it is

agreed amounted to an injury which is a disease) was an

injury to which his employment contributed to a substantial

degree, so as to bring the respondent within the Act,

s25(1)(b), when there was no evidence upon which it was open

to him to so conclude;

(b) in concluding that the incapacity of the respondent

since 25 February 1993 resulted from the injury suffered by

the respondent on 27 December 1990 when there was no

evidence upon which it was open to him to so conclude; and

(c) in failing to give any sufficient or adequate reasons

for determining the application in favour of the respondent.

7. The grounds of appeal also raise some other alleged errors of law. To the extent that they do so, they are without merit and are incapable of affecting the outcome of the appeal so that it is unnecessary to give any further consideration to them.

8. The respondent was an ambulance officer employed pursuant to the provisions of the Tasmanian State Service Act 1984, performing duties for the Tasmanian Ambulance Service. Prior to 27 December 1990 he had been suffering from ischaemic heart disease which had been diagnosed in 1989. On the evening of that day he was engaged in the duties of his employment at the Claremont ambulance station. A call was received to attend a house at Glenorchy where it was believed there was a person who had taken a drug overdose. The respondent and another officer attended in response to that call, the respondent driving the ambulance. Some time after the ambulance arrived at the patient's house the respondent felt chest pains. The pains were of such severity that the respondent felt unable to drive the ambulance. He sat in the front passenger seat whilst it was driven to the Royal Hobart Hospital by a police officer. His fellow officer travelled with the patient in the rear of the ambulance. At the hospital the respondent received medical attention and it was ascertained that he had suffered an acute myocardial infarction. An angiogram was performed and this disclosed a seventy per cent stenosis in the left anterior descending artery.

9. The respondent spent some time as an in-patient at the hospital and thereafter convalesced at home. Some three months after his heart attack he returned to work and continued to perform his normal duties until 12 April 1992. On that day he was performing duties at a rugby ground attending a patient thought to have suffered a cardiac arrest. As he attended to this patient other persons at the ground were abusive and threatening towards him and that distressed the respondent. He transported the patient to hospital and on arriving there felt some tightness in the chest. He took some medication, rested for a while and then returned to the ambulance station. After the respondent had returned to the station, the pain, which had eased after the respondent had taken medication, returned and increased in intensity. The respondent was admitted to hospital where it was ascertained that he had suffered a minor myocardial infarction. There followed a period as an in-patient and a subsequent period of convalescence. After about two months the respondent returned to work. He made a claim for compensation in respect of the period of incapacity following the injury of 12 April 1992 and compensation was paid as claimed.

10. Whilst at work on 25 February 1993 the respondent suffered central chest pain. He sought medical attention. Tests were carried out as a result of which it was ascertained that the respondent was suffering from angina but had not suffered any further myocardial infarction. The respondent has not worked since 25 February 1993.

11. Four separate claims for compensation have been made by the respondent. Those claims were as follows:

Date of claim Date of alleged injury Nature of alleged

injury

8 February 1994 27 December 1990 Acute myocardial

infarction

3 June 1992 12 April 1992 Acute myocardial

infarction

22 March 1993 25 February 1993 Cardiac angina

22 March 1993 25 February 1993 Ischaemic heart

disease

12. The first of these claims was the subject of the respondent's application of 14 April 1994 which resulted in a determination favourable to him and which is the subject of this appeal. The second of those claims was met in relation to the period of incapacity immediately following the injury but nevertheless was the subject of the respondent's application of 9 July 1993, upon the basis that a further period of incapacity, commencing on 26 February 1993, had resulted from it. The other claims were not the subject of any reference to the Commissioner. Despite that, the learned Commissioner, in his written reasons, wrote:

"Therefore in relation to the two claims for compensation

both made on the 22nd of March 1993 for ischaemic heart

disease and for angina I would dismiss the worker's

application and there will be an order accordingly."

13. The claims for compensation made by the respondent on 22 March 1993 had not been referred to the Commissioner by any person so that there was no occasion to dismiss any application concerning them. There was no such application. The only order dismissing an application made by the Commissioner was that which concerned the claim made on 3 June 1992 but he expressed no reasons for making such an order. It seems that the learned Commissioner was confused as to what was before him and proceeded upon the mistaken assumption that the respondent's application of 9 July 1993 effected a reference of the claims for compensation made on 22 March 1993. I mention this aspect of the matter, not because it is directly raised by any ground of appeal, but because it is illustrative of the general difficulties which I have had in attempting to follow the reasoning processes disclosed by the learned Commissioner's reasons for his determinations.

14. The effect of the Act, s25(1)(b) is that before the respondent established an entitlement for compensation arising out of the occurrence on 27 December 1990, he was required to satisfy the learned Commissioner:

(a) that he had suffered an injury;

(b) that the injury arose out of and was suffered in the

course of his employment; and

(c) that the injury was an injury to which his employment

contributed to a substantial degree.

15. The first two of those matters were established by the evidence and the Commissioner found accordingly. It has not been asserted that the Commissioner erred in so finding. The grounds of appeal are directed to the third of those matters. The learned Commissioner relied on the recent decision of the Full Court in University of Tasmania v Cain A43/1994 for the proposition that the employment of a worker may be said to have contributed to an injury suffered by him to a substantial degree if the employment contributed to the injury "to more than a trivial or inconsequential degree". In that case Slicer J (with whom Cox J agreed) said at 3:

"The legislation requires a causative link between the

employment and the incapacity. It differs from other

legislative schemes in requiring a 'substantial degree' of

causation. But it does not seek to quantify the term in an

absolute sense. It does not attempt to fix a percentage or

exclude the operation of other contributory factors. It

does not attempt to exclude predisposition or susceptibility

to a particular condition. The term relates directly to the

work related cause requiring it to be more than trivial or

inconsequential. It is relative to the cause and is not to

be taken as one component to be compared with and weighed

against other possible causes. The word itself is not

quantitative in relation to the whole. See Tilmann's

Butcheries Pty Ltd v AMIEU [1979] FCA 85; (1979) 42 FLR 331."

16. The third member of the Court, Wright J (with whose reasons Cox J also agreed) stated the relevant test in less prescriptive terms but nothing that his Honour said is inconsistent with the formulation adopted by Slicer J. In my view I am bound by that formulation of the relevant test. The appellant submitted that the relevant observations made by the members of the Full Court were obiter. I do not agree. Even if the formulation of that test was obiter it would be quite inappropriate for me not to follow it.

17. The appellant submitted that the test formulated by Slicer J means no more than that if the employment of a worker has contributed to an injury which is a disease to a degree which is trivial or inconsequential there is no entitlement to compensation, without being concerned with what is a sufficient degree of contribution to constitute contribution to a substantial degree. I do not accept that submission. Any contribution which is more than to a trivial or inconsequential degree is a contribution to a substantial degree for the purposes of s25(1)(b). That appears to be the test stated by the learned Commissioner as being the appropriate test and he was correct in that respect.

18. This was a case where it was absolutely critical that very careful findings of primary fact be made. In order to be able to conclude whether it had been established that the employment of the respondent had contributed to his injury to a substantial degree findings of fact needed to be made as to whether any, and if so which, aspects of the respondent's employment had contributed to his injury. As nothing which occurred after the respondent suffered his injury would have been capable of contributing to it, it was necessary that the learned Commissioner determine when the respondent suffered his injury and that he find the primary facts leading to such determination.

19. The only findings of fact made by the learned Commissioner which were relevant to those issues appear from the following excerpts from the written reasons for his determinations:

"On the 27th of December 1990 I find .... that the

myocardial infarction was caused by the rupture of the

plaque like material forming in the left anterior descending

artery of the worker's heart. .... Clearly the worker had

a severe heart attack at that stage. I find that this heart

attack occurred at the time that he was attending to his

duties as an ambulance officer and when he was involved both

in a stressful and physically exerting situation. Likewise,

if it was thought necessary, the situation in 1992 when

attending the rugby ground incident, although I note that it

cannot be said that such a stressful and physically exerting

incident occurred in February 1993 when the worker suffered

angina.

...

In this particular case the evidence discloses that the

worker was engaged in a stressful situation treating a

suspected drug overdose patient at the time that the heart

attack occurred. Not only was he involved in driving the

ambulance to the overdose patient, but he had to carry the

resuscitation unit down a driveway to the residence and was

uncertain what he would find when he got there. When he

found the patient he started to suffer from central chest

pain and had to run back up the driveway to the vehicle to

back the vehicle down the driveway so that the patient could

be taken to hospital at which time he suffered from

increased pain, shortness of breath, sweating and nausea."

20. The effect of these findings appears to be that the learned Commissioner was satisfied that the respondent suffered his injury at the time that he found the patient and that immediately prior to that he had driven the ambulance, carried a resuscitation unit from the ambulance along a driveway to the patient and had been subjected to the stress of not knowing precisely what he would find when he located the patient. It is necessary to consider the evidence which was relevant to those matters.

21. Before going to that evidence I make one observation about the use made by the learned Commissioner of authority. He appears to have relied on Delahunty v The Commonwealth [1981] FCA 8; (1981) 53 FLR 9 and Park Royal Motor Hotels Pty Ltd v Sullivan (1985) 61 ACTR 15, not as authority for any proposition of law, but for the proposition that stress or exertion may lead to a person having a heart attack. He said that such a conclusion was "supported by the finding of" the former case and "suggested by the court" in the latter case. It is of course trite that a finding of fact made by one court on the evidence before it is incapable of supporting a finding of fact in another case. Insofar as the Commissioner relied upon such material for making a finding of fact he was in error.

22. In examination-in-chief the respondent gave the following account of the relevant events. He had commenced his shift on 27 December 1990 at 6pm. At about 6.45pm there was received a call to attend a patient who had taken a drug overdose. The respondent drove the ambulance from the Claremont station to the house at Glenorchy where it was believed the patient would be found. There was a reasonable amount of traffic on the roads. Upon arriving at the house the respondent obtained a drug box, resuscitator and other equipment from the ambulance and carried it whilst walking along a driveway from which he entered the house where he found the patient. The total distance from the ambulance to the house was some twenty metres. At the time that he found the patient the respondent felt a central chest pain of a type which was of a type he had not earlier experienced and the severity of which increased during the course of attending to the patient. The respondent ran back along the driveway to get a stretcher and that increased the pain. He and the ambulance officer who had accompanied him lifted the patient onto the bed whereupon the respondent started to get shortness of breath, felt nauseous and started to perspire. The patient was placed in the ambulance by persons who were not identified. There then followed the drive to the hospital and the subsequent events to which I have already referred.

23. The respondent called a consultant physician Dr Loughhead. Dr Loughhead adopted the contents of two reports earlier prepared by him and those reports were tendered. The first of those reports, dated 6 June 1994, contains the following passages:

"He (ie the respondent) was first seen on 27/12/90 in the

Accident and Emergency Department by Dr Carol Lance. She

records that he developed central chest pain which radiated

down both arms with associated marked sweating after he had

picked up a patient suffering from an overdose. Because of

his condition he was unable to drive the ambulance and a

police officer drove the ambulance to the Royal Hobart

Hospital. His only previous symptom earlier that evening

had been some slight diarrhoea.

.... This patient had a heart attack whilst picking up a

patient in the course of his duties.

.... I say therefore that it is conclusive that the heart

attack occurred at the time of work in a patient with

otherwise trivial coronary artery disease. It cannot be

said that his original heart attack was not related to his

work and in very great probability, it is specifically

related to his work."

24. It follows that the respondent put before the Commissioner evidence that on admission he had informed the hospital medical officer that the first relevant symptoms of which he had been aware were pain and sweating after he had picked up the patient. Although that is a version of the facts not entirely consistent with that given by the respondent in examination-in-chief, no attempt was made to reconcile the two and no cross-examination was directed to the discrepancy. What was said to be the version of events related by the respondent in examination-in-chief was put to Dr Loughhead with an invitation to express an opinion. Dr Loughhead gave the following evidence:

"Now, the history provided by Mr Smith this morning has been

that on the 27th of December 1990 he was attending an urgent

call and he drove the ambulance some distance to where a

patient had taken an overdose, he does some running to and

from the ambulance, takes the patient into the Royal Hobart

Hospital, but during that running between the house and the

ambulance he feels chest pain, central chest pain, and that

ends up in getting him into the Royal Hobart Hospital as

well, is that the history that you understand to be the

case? ... I couldn't the (sic) fine details of the history

as given to me when I saw him in December of 1990, that is

reasonable (sic) recollection.

Yes, and in your opinion did Mr Smith's employment at that

time as an ambulance officer contribute to his myocardial

infarction? ... I think that's a very probable circumstance.

And was the part paid (sic) by his employment more than

trivial or inconsequential to myocardial infarction? ...

Well, if as I believe the stress of that event was the

initiating factor in his heart attack then it's the cause of

the actual heart attack."

25. The clear suggestion made to Dr Loughhead was that the onset of pain occurred whilst the respondent was running between the house and the ambulance. That was not the effect of the respondent's evidence. He had said that the pain commenced before he had engaged in any running and that his subsequent running increased the level of pain. In cross-examination of Dr Loughhead the following exchange occurred:

"Mr Smith's given evidence that he went to a drug overdose

and he was going to get the - he'd gone into the residence

and getting some equipment and went to get the stretcher out

of the ambulance and experienced some chest pain. Now, are

you saying that that level of exertion can be conclusively

said to have brought about his heart attack? ... No, I'm not

saying that it can be conclusively said, I thought I made it

clear that I cannot say with certainty, I'm saying that on

the balance of probabilities, it's much more probable than

not that they are associated."

26. The appellant called a consultant cardiologist, Dr Bowman. In the course of the cross-examination of that witness the following exchanges occurred:

"Well the evidence that has been given today is that Mr

Smith drove through traffic to a patient who had taken an

overdose. He describes even the driving of the ambulance as

being quite stressful and then arrives and does some

physical exertion in amongst that and has the chest pain at

that time and in the result has a myocardial infarction.

Again do you agree with me that the undertaking of that work

contributed to the myocardial infarction? ... I believe it

certainly contributed to it but as I mentioned previously I

think that wouldn't happen in a normal person, you'd have to

have some underlying coronary artery disease for that degree

of stress and exertion to bring on a heart attack.

And you would again agree with me that the part played by

the work he was undertaking was more than trivial or

inconsequential? ... The statement here is that he was

walking down a drive with a drug box and got chest pain,

that's the first time he had chest pain."

27. The respondent had not given evidence that the driving of the ambulance was at all stressful so that the version of events upon which Dr Bowman expressed his opinion was no more than hypothetical. The opinion of an expert witness based upon assumed facts is of no value unless those facts are proved (cf Ramsay v Watson [1961] HCA 65; (1961) 108 CLR 642).

28. However there were even more substantial difficulties in acting on the opinions expressed by the doctors because the version of relevant events put to them was markedly different from the version given by the respondent in cross-examination. That version was given by the respondent when, at the outset of his cross-examination, he was asked to again recount the relevant events. In particular the respondent gave the following evidence:

"When did you first feel the pain? .... It first of all

became aware to me as I was getting out of the vehicle and

getting the equipment out.

So when you first arrived? .... It started to develop,

yeah started to develop a little bit of central chest pain

then.

Right. And that was after you'd driven, you said you'd

driven the ambulance? .... Yes."

29. The medical witnesses were asked nothing about whether the mere driving of the vehicle might have contributed to the respondent suffering his heart attack although the evidence of the respondent left open the finding that the respondent had suffered a heart attack before engaging in any physical exertion after arriving at the house.

30. Undoubtedly the reason for the version of events given by the respondent in cross-examination not having been put to the medical witnesses is that when they gave their evidence the respondent had given his evidence-in-chief but had not been cross-examined. That was a most unsatisfactory procedure and one which was fraught with danger. To ask a medical witness to assume facts and then to express an opinion based on those assumed facts before it is known what the evidence will be as to the existence of those facts gives rise to the real danger that the opinion expressed will have no evidentiary value. Surprisingly there was no application for leave to recall either of the medical witnesses after the respondent had completed his evidence. Counsel for the respondent conceded that as his client carried the onus, it would have been for him to make such an application to enable the version of events given by the respondent in cross-examination to be put to the doctors.

31. It was at the instance of the Commissioner that the medical witnesses were interposed after the examination-in-chief of the respondent. During the course of opening her case, counsel who appeared for the respondent in the court below indicated that arrangements had been made for the medical witnesses to attend later in the day. The Commissioner then immediately observed "well we'll interpose them if - they're both busy men". With respect to the learned Commissioner, the order in which witnesses were to be called was a matter for the parties. It was entirely inappropriate for the medical witnesses on both sides to give their evidence before the respondent had closed his case or had even been cross-examined. Courts always are conscious of the extent and nature of the obligations of medical witnesses and are ready to take steps to ensure that any interference with the discharge of their professional obligations is kept to a minimum. However that ought not to be taken to the extent of obsequiousness on the part of a court by requiring that a medical witness is called at the precise time at which he has been asked to attend, regardless of the stage which the proceedings have reached and regardless of the injustice which may be caused thereby.

32. The appellant has raised as a ground of appeal what is said to be an error of law on the part of the Commissioner in failing to give any sufficient or adequate reasons. As Underwood J has recently explained in Australian Securities Commission v Schreuder A79/1994, it is "an incident of judicial duty to give adequate reasons for judgment and that a failure to do so constitutes an error of law." His Honour was speaking of the common law duty. The Act, s61(3) imposes an express obligation on the Commissioner to provide a written statement of his reasons for making a determination which is given effect to by an order in respect of a claim for compensation. The principles expressed by Underwood J are of equal application to the statutory duty imposed by s61(3). An application of those principles required that the Commissioner:

1 make findings with respect to the essential facts relied

upon by the parties relevant to the references before him;

2 where the evidence with respect to any fact was in dispute

or unclear, state the basis for making a particular finding

in respect thereof;

3 where appropriate, state the inferences drawn from the

facts found and, where necessary, the basis for drawing such

inferences;

4 expose the reasoning process which resulted in his

determination to the scrutiny of the parties and any

appellate court.

33. The finding made by the learned Commissioner that the respondent first suffered central chest pain, and by inference that it was then that he suffered a heart attack, at the time that he found the patient and after he had carried equipment whilst proceeding along a driveway is surprising when such a finding was quite inconsistent with what the respondent had said in cross-examination. Whilst there was some ambiguity in the evidence given by the respondent in cross-examination, it is clear on one point, namely that he first felt the pain before reaching the patient or even commencing to walk along the driveway.

34. With such inconsistencies in the evidence given by the respondent and with evidence of the respondent having given yet a third version upon his admission to hospital, it was incumbent upon the learned Commissioner to do much more than merely make a finding in accordance with what the respondent had said in evidence-in-chief. He was required to state his reasons for finding one version of the relevant facts rather than either of the competing versions. Normally, where a witness resiles from evidence which he has given one would not expect the facts to be found as originally stated. There would need to be good reason for so finding the facts. It is imperative that the reasons for such a finding are clearly articulated. A failure to do so is an error of law because it is an error not to state the basis for making findings of fact where the evidence in respect thereof is in dispute or unclear. Such a failure gives rise to the suspicion that the judicial officer has overlooked some of the evidence and has erroneously assumed that the relevant matters of fact are not in dispute.

35. In at least one other respect the learned Commissioner gave quite inadequate reasons for his determination. After having made the findings of fact which I have reproduced at page 5 of these reasons, the Commissioner expressed his reasons for concluding that the injury fell within s25(1)(b) as follows:

"... there appear to be no other causes at the time of the

suffering of the injury which could have led to the injury

save and except for a suggestions that the plaque in the

artery may have naturally ruptured by itself as a result of

the progression of the heart disease. This assertion which

is a possibility is in my view to be viewed in the light of

the evidence of the cardiologists who both, as I have said,

take the view that stressful incidents can lead to the

rupturing of plaque. This is also supported by the finding

of Delahunty's case (supra).

I am therefore of the opinion that the worker succeeds in

relation to his claim for compensation as a result of the

suffering of a heart attack at work on the 27th of December

1990. There will be an order that he be paid for periods of

incapacity resulting from that heart attack."

36. Those reasons cannot possibly justify the conclusion reached by the Commissioner. A mere statement that there are two possible causes of an injury does not justify a conclusion that one or other is to be preferred. The Commissioner gave no reasons at all for preferring one possible cause to the other. He was required to do so. His reference to Delahunty v The Commonwealth (supra) was misconceived.

37. For these reasons I have concluded that the learned Commissioner erred in law by failing to give sufficient reasons for his determination. That is sufficient to determine this appeal in favour of the appellant and it is unnecessary to express any further views about any other ground of appeal.

38. Counsel were agreed that, in the event that I were to reach the conclusion which I have reached, the matter ought to be sent back for rehearing before another Commissioner. Accordingly I order that the appeal be upheld, that the determination and order made by the Workers Compensation Commissioner in reference 381/1994 be set aside and that the reference be remitted for rehearing before a part-time Workers Compensation Commissioner appointed under the Act.