State of Tasmania v Parson [2002] TASSC 59, 11 Tas R 56; St Helens Oysters Pty Ltd v Coatsworth [2007] TASSC 90, 17 Tas R 43; Vos Construction & Joinery Pty Ltd v Norton Smith [2016] TASSC 38, applied.

Workers Compensation - Entitlement to compensation - Injury, disease or disability - Disease - Aggravation or acceleration of pre-existing disease or condition - General principles - Causation - Employment major or most significant contributing factor to aggravation, acceleration, exacerbation or deterioration of pre-existing disease.

Workers Rehabilitation and Compensation Act 1988 (Tas), ss 81A, 63, 25.

Long v Kmart Australia Ltd [2016] TASSC 6, 25 Tas R 237, applied.

Workers Compensation - Proceedings to obtain compensation - Preliminary requirements - Interim payments - Reasonably arguable case for employer established - Tribunal erred.

Judgment Number: [2019] TASSC 41

1. On 21 May 2018, the appellant made a claim for workers compensation in respect of an injury which was asserted to have occurred on 4 May 2018. The appellant was employed by the respondent as a stores person in a warehouse, and had been in that employment for many years. The claim asserted that after driving a "battery reach fork", as he walked away, he felt severe pain in his lower right back and pain through his right hip. The claim form was accompanied by medical certificates which certified incapacity for work from 7 May 2018.
2. The respondent arranged for the appellant to be examined by a neurosurgeon, Mr Dohrmann. On 24 July 2018, pursuant to s 81A of the Workers Rehabilitation and Compensation Act 1988 (the Act), the respondent served a notice on the appellant disputing liability to pay compensation and referred the matter to the Workers Rehabilitation and Compensation Tribunal (the Tribunal). The asserted basis of dispute was that it was reasonably arguable that the worker had not suffered an injury which gave rise to liability on the part of the employer to pay compensation pursuant to the Act. On 7 August 2018, the Tribunal, constituted by Commissioner Wilkins, conducted a hearing and determined that a reasonably arguable case existed concerning that question. The Tribunal ordered that compensation not be paid.
3. The appellant has now appealed to this Court from that determination. The appeal is authorised by s 63 of the Act, but is limited to a complaint about the determination "in point of law". The appellant relies on a number of grounds, but the gravamen of the appellant's argument is that the only reasonable conclusion open to the Tribunal on the material before it was that the worker had suffered an injury for which the respondent was liable to pay compensation, and therefore, as a matter of law, it was not open to the Tribunal to find that the respondent had established a reasonably arguable case about that matter. The respondent argues to the contrary. The appeal raises the issues of liability and causation, and its resolution turns on the ambit of the claim, and the effect of Mr Dohrmann's written opinion in relation to the nature and cause of the appellant's injury.
4. The respondent also referred to the Tribunal the question of the payment of expenses pursuant to s 77AB of the Act. The issues and the Tribunal's determination of this referral were identical to the s 81A referral. This determination is not expressly included in the appeal, but if it had been, the arguments and outcome would mirror those relevant to the referral relating to weekly payments.

The s 81A referral

1. The scheme implemented by s 81A is that an employer who disputes liability in respect of a claim for compensation, must serve a notice of dispute on the worker, which informs the worker of the reasons for the dispute, and must then refer the matter to the Tribunal. The employer must do this within 84 days of receiving the claim. If this is not done within that time, the employer will be taken to have accepted liability in respect of the claim (s 81AB). Upon referral, the Tribunal must order the employer to make the specified payments unless it considers that "a reasonably arguable case exists concerning the liability of the employer to pay compensation", in which case it shall determine that compensation is not to be paid by the employer. The Act therefore establishes "a relatively speedy process for assessing whether an employer, who wishes to dispute liability to pay weekly compensation, has a reasonably arguable case in that regard ..." (per Crawford J (as he then was) in Walker v J and A Freeman Building Services [2006] TASSC 90, 16 Tas R 87). This process is consistent with the beneficial nature of the legislation.
2. It is well established that the employer bears the onus of demonstrating the existence of a reasonably arguable case that compensation is not payable: Skill Group Limited v Anning [2015] TASSC 18, 23 Tas R 463; Lamont v M R V Supermarkets Pty Ltd [2016] TASSC 16, 24 Tas R 234. The section requires the employer to compile and deliver evidentiary material: s 81A(2)(b). The test to be applied by the Tribunal on the referral has been described in the following terms:

"a reasonably arguable case will exist concerning the liability of an employer to pay a worker if it is reasonably arguable on the material available in relation to the claim or identified deficiencies or weaknesses in the claim that, following a contested hearing it may be rejected."

St Helens Oysters Pty Ltd v Coatsworth [2007] TASSC 90, 17 Tas R 43.

1. It is not sufficient for the employer to indicate that it simply wishes to put the worker to proof: Vos Construction & Joinery Pty Ltd v Norton-Smith [2016] TASSC 38, per Pearce J at [5].

1. The evidence before the Tribunal was confined to the documents placed before it by the respondent. This included the claim form, the medical certificates provided by the appellant to the respondent, and two reports by Mr Dohrmann.
2. The claim form asserted that injury had occurred on 4 May 2018 at 8.50 am, in the following circumstances:

"Whilst driving battery reach fork to complete a job. I finished and felt severe pain lower right of my back & pain out through my right hip when I walked away from battery reach fork."

It described the injury as "severe pain" and the body part most affected as "lower right back".

1. The certificates which accompanied the claim included the following:

(a) A certificate dated 7 May 2018 from a general practitioner, Dr Yong. This certificate was not in the form approved by the WorkCover Tasmania Board, as is required by s 34(1)(b) of the Act. It asserted that the appellant would "be unfit to continue his usual occupation", but did not contain any reference to the claimed injury. It was, therefore, incapable of supporting the payment of compensation by way of weekly benefits pursuant to s 69 of the Act.

(b) A document described as an "Initial Workers Compensation Medical Certificate" in the form approved by the Board, was signed by Dr Michael Jackson. It is dated 17 May 2018 and asserted incapacity for work between 17 May and 17 June 2018. I will return to the contents of this certificate later in these reasons.

1. It is common ground that the reports of Mr Dohrmann are critical to the determination of this appeal. Indeed, the respective submissions of counsel for each party largely consisted of a purported interpretation of the effect of Mr Dohrmann's comments. The first report, dated 4 July 2018, was comprehensive. It summarised the appellant's background, the result of Mr Dohrmann's examination and investigations, and his opinion. Some pertinent aspects of this report are as follows:
   • As at 4 May 2018, the appellant, who was then aged 58 years, had been working full-time as a store person in the same place of employment for 35 years. It is common ground that he had only been employed by the respondent since 27 July 2009, but before that was employed in the same capacity by a corporation which was the statutory predecessor of the respondent.
   • For the past 8 years, while he had been employed by the respondent, the appellant had been using a reach fork to perform approximately 90% of his daily work. The use of this implement involved repeated head movements and twisting movements of the trunk to right and left, as well as looking upwards. There was also considerable bending and lifting of weights.
   • Mr Dohrmann summarised a considerable history of back pain and consequent treatment. This had included a previous cervical fusion. The appellant had been having low back pain since about 2016, and had further surgery on his lower back in that year. There had been ongoing symptoms, including sciatica leading up to the claimed injury.
   • The report noted that on 14 May 2018, the appellant underwent a nerve block for right sided leg symptoms. It was observed by counsel for the respondent at the hearing before the Tribunal, that this procedure had been arranged by Dr Jackson on the day prior to 4 May 2018. Despite this, the appellant claimed to Mr Dohrmann that immediately before 4 May 2018 "he had no neck symptoms, no low back pain, but was suffering from a little right sciatica".
   • The appellant's description of the onset of symptoms on 4 May 2018 was recorded in Mr Dohrmann's report as follows:

"He said that on 04.05.2018 he had been using a reach fork from which he alighted after parking the vehicle. He said that he took two steps and then developed severe right-sided low back pain which caused him to double up on the floor. He said the pain was by far the worst low back pain that he had experienced and that he had to go home early and has been unable to work since that date."

1. Mr Dohrmann expressed his opinion in response to specific questions from the respondent's solicitor. The following questions and answers are of particular relevance to this case:

"4 What is your diagnosis of the current condition?

Mr Bradshaw is currently suffering from an aggravation of lumbar spondylosis.

1. In your view has the worker on 04.05.2018 sustained an injury or a disease? A disease refers to a condition that develops, although that development may be sudden, whereas an injury is as a result of a sudden external traumatic event involving some physiological change.
   1. If in your view the worker has sustained a disease, is his work and\or/the events of 04.05.2018 the major or most significant contributing factor to the development of that disease?
   2. If the worker has suffered an injury do you believe the injury arose out of or in the course of the worker's employment with the employer on 04.05.2018?

I consider that Mr Bradshaw has suffered an injury taking the form of an aggravation of pre-existing lumbar spondylosis which occurred in the course of his employment on 04.05.2018.

1. The Tasmanian legislation also defines an injury to include 'the recurrence, aggravation, acceleration, exacerbation or deterioration of any pre-existing injury or disease where the employment was the major or most significant contributing factor to that recurrence, aggravation, acceleration, exacerbation or deterioration'. Can you comment on whether Mr Bradshaw, on 04.05.2018, has sustained an injury in this context?

Noting the definition in the Tasmanian legislation, I consider that Mr Bradshaw has suffered an injury in this context. I think that the injury needs to be seen in the context of his employment over 35 years and noting the inherent requirements of the role, I further note that Mr Bradshaw has used a reach fork for the past eight years and has described daily activities which include regular twisting motions of the trunk. It is in this respect that I believe that a reasonable argument can be made that his employment has been a major contributing factor to the aggravation of lumbar spondylosis from which he now suffers.

While it is realised that Mr Bradshaw did not suffer any specific incident on 04.05.2018, in that he was simply walking a couple of steps when he experienced back pain, I think that the work-related causation of his current lower back condition needs to be seen in a much longer context."

1. Also before the Tribunal was a letter which the respondent's lawyer had written to Mr Dohrmann after receiving the first report. That letter asserted a number of propositions to Mr Dohrmann for comment. In response, Mr Dohrmann provided a further report dated 23 July 2018. The following are selected extracts from that report:

"• In respect to point 3, I would accept that Mr Bradshaw did not suffer a traumatic incident on 04.05.2018. However, I consider that the acute symptoms he experienced on that day, while spontaneous in onset, were due to pre-existing lumbar spondylosis to which employment over a long period of time has made some contribution.

• ... it is reasonable to conclude that there was no specific incident or accident, and therefore no particular event or activity, that caused injury on 04.05.2018.
• In respect of point 11 on page 3 of your letter, it remains my view that Mr Bradshaw was suffering from lumbar spondylosis, where his employment has contributed to the acceleration of that condition by way of aggravation over many years, and perhaps more specifically over the past eight years or thereabouts, during which time I understand he has been regularly using a reach forklift. He was therefore suffering from a work-related condition on 04.05.2018, but this was the same condition that he was suffering from prior to that date. I can confirm that Mr Bradshaw appears not to have suffered a specific work-related injury on 04.05.2018."

1. Before the Tribunal, the respondent relied solely on the material described above. There was no oral evidence and the appellant did not present any evidence.
2. The respondent's primary submission was that on the basis of Mr Dohrmann's reports, it was reasonably arguable that the appellant had not suffered a work related injury on 4 May 2018. It was conceded that there may well have been a pre-existing condition which was work related, but that the claim related to an injury in the primary sense (s 25(1)(a)) which had occurred on 4 May 2018, and Mr Dohrmann's opinion was that there was no work related event or activity on that date that resulted in a such an injury. In the event that the claim included the possibility that the symptoms experienced by the appellant could be regarded as an aggravation of a pre-existing disease (s 25(1)(b)), which was not conceded, there could only be liability if the requisite causal link was established between employment activity on 4 May and the aggravation. It was argued that this could not be established on the evidence before the Tribunal.
3. The learned Commissioner accepted these arguments, and determined that there was a reasonably arguable case concerning the liability of the respondent to pay compensation. She provided brief oral reasons for this decision. The relevant portion is as follows:

"I am satisfied that there is a reasonably arguable case to dispute this claim based on Mr Sweeney's submissions. Whilst it does appear to be incontrovertible from Dr Dohrmann's opinion that there may well have been an underlying condition to which Mr Bradshaw's work may have contributed over many, many years, the claim itself is for an incident or injury, rather, occurring on the 4th of May 2018 and similarly the initial workers compensation medical certificate supporting that claim refers to an incident on the same date and I accept Mr Sweeney's submissions that a fair reading of Mr Dohrmann's opinion as contained in the totality of his two reports is enough for there to be an arguable case that nothing satisfying the definition of injury within the Workers Rehabilitation and Compensation Act happened on that date."

1. The notice of appeal asserts a number of grounds. The majority can be distilled into a single proposition, which is that it was not open to the Tribunal on the evidence before it to find that it was reasonably arguable that the employer was not liable to pay compensation. One ground (ground 2), attacks the reasoning of the Commissioner in accepting the respondent's counsel's submission that it was necessary to establish a causative link between the appellant's work on 4 May and the injury or aggravation in order to establish the respondent's liability to pay compensation.
2. The respondent's argument is that there was no error in reasoning and, in any event, the Commissioner has reached the correct conclusion on the material. In particular, it is argued that Mr Dohrmann's opinion, as expressed in the two reports, and interpreted on the basis most favourable to the employer, leaves open a reasonable argument that the respondent was not liable to pay compensation. There are two limbs to the purported argument, which are:
   • The employer's liability is limited by the nature and ambit of the claim. This claim was for a specific work related injury which occurred on 4 May 2018. On the basis of Mr Dohrmann's evidence, it is reasonably arguable that there was no such injury.
   • Even if the ambit of the claim is wide enough to encompass the recurrence, aggravation, acceleration, exacerbation or deterioration (these substantives are hereafter collectively referred to as "aggravation") of a pre-existing injury or disease, it was reasonably arguable that:
     • There was no such aggravation on 4 May 2018, but simply the ongoing natural progress of the pre-existing condition.
     • In any event, it was reasonably arguable that the necessary relationship between work and the aggravation of the pre-existing condition did not exist.

1. The liability of an employer to pay compensation arises by virtue of s 25(1) of the Act. That section provides as follows:

"25 Liability of employers to compensate workers for injuries

(a) a worker suffers an injury, not being a disease, arising out of or in the course of his employment; or

(b) a worker suffers an injury, which is a disease and to which his employment contributed to a substantial degree, within the meaning of section 3(2A) -

his employer is, except as is otherwise provided by this Act, liable to pay compensation in accordance with this Act -

1. Section 3 of the Act contains the following definitions:

"disease means any ailment, disorder, defect, or morbid condition, whether of sudden or gradual development;

(b) the recurrence, aggravation, acceleration, exacerbation or deterioration of any pre-existing injury or disease where the employment was the major or most significant contributing factor to that recurrence, aggravation, acceleration, exacerbation or deterioration -

1. Section 3(2A) provides:

"(2A) For the purposes of this Act, employment contributed to a disease to a substantial degree only if it is the major or most significant factor."

1. The effect of s 25(1) is that the employer's liability to pay compensation will arise where the worker has suffered an injury as defined, in the circumstances prescribed by that section. In respect of the two pathways to liability created by the section, Pearce J, in Vos Construction & Joinery Pty Ltd v Norton-Smith (above), said at [23]:

"[23] There is no dichotomy between an injury which is a disease and an injury which is not a disease. A worker is entitled to recover if he or she falls within either head of recovery: Zickar v MGH Plastic Industries Pty Ltd (1996) 187 CLR 310 per Kirby J at 351, applied by McHugh, Gummow and Hayne JJ in Kennedy Cleaning v Petkoska at 310 [73]."

1. The authorities also establish that when regard is had to the extended definition of injury contained in subpar (b), there are in fact three available pathways to liability arising from s 25(1). These are:

(a) The worker suffers an injury in the primary sense, that is an injury which is not a disease, but is "something that can be described as a sudden and ascertainable or dramatic physiological change or disturbance of the normal physiological state". See Military Rehabilitation and Compensation Commission v May [2016] HCA 19, 257 CLR 468, as discussed by Pearce J in Vos Construction v Norton-Smith. Such an injury will be compensable if it arises out of or in the course of the worker's employment.

(b) The worker suffers a disease to which his employment contributed to a substantial degree within the meaning of s 3(2A), that is, only if it is the major or most significant factor.

(c) By virtue of the extended definition of injury and its interaction with s 25(1)(b), an aggravation etc of a pre-existing injury or disease is an injury, but only where the employment was the major or most significant contributing factor to that aggravation. In the case of the aggravation of a pre-existing disease, it is the aggravation, not the underlying disease, which must be causally connected to the employment in the required sense: Long v Kmart Australia Ltd [2016] TASSC 6, 25 Tas R 237, per Porter J at [52].

1. The employer's liability to pay compensation and the Tribunal's jurisdiction to determine the dispute about that liability depends upon and is therefore circumscribed by the claim. As already discussed, the claim must be for an injury which occurs in the circumstances prescribed by s 25 if it is to give rise to liability to pay compensation.
2. The respondent argues that the ambit of the claim is defined by two documents, the claim form and the initial medical certificate. This submission relies upon s 34 of the Act which requires a claim for compensation:

(b) be accompanied by a certificate in a form approved by the Board signed by a medical practitioner or an accredited person.

1. The respondent submits that, in this case, those documents confine the claim to one for an injury in the primary sense under s 25(1)(a). The claim does not relate to an injury being an aggravation of a pre-existing disease within the extended definition. The basis of this submission is that, in the medical certificate, the doctor has ticked boxes which have the effect of certifying the following information:
   • "The above named worker stated the condition to be caused by ... an incident which occurred on 4 May 2018." The doctor did not tick the alternative box which was worded "A disease, symptoms of which became evident on ...".
   • "If known the injury or disease is ... a new condition". The doctor did not tick boxes which provided for:
     • A recurrence of a previously compensable condition.
     • An aggravation of an existing condition.
2. The respondent's argument is that the claim is constrained accordingly, and therefore limited to an injury under s 25(1)(a), which occurred on 4 May, and arose out of or in the course of employment on that day. It is argued that it would be unfair and contrary to the legislation to require the employer to consider and deal with a claim relating to an injury of a different nature and under a different pathway, when such an alternative claim is not within the certification contained in the medical certificate.
3. I do not accept this submission. It is clear that the claim must identify the injury which is said to give rise to the liability to pay compensation. However, the only requirement for that liability is that the identified injury falls within the ambit of s 25. As Pearce J noted in Vos Constructions v Norton-Smith, there is no dichotomy between the limbs of s 25. Because of the extended definition, his Honour's observation must also be taken to include an aggravation, etc. There is nothing in the Act which requires the worker, in the claim, to identify the pathway under s 25 which will make the injury in question compensable. Such a requirement would be contrary to the beneficial nature and scheme of the Act. What is required is that the employer have sufficient information from the claim to be able to identify, as a matter of fact, the injury which is asserted to give rise to the liability to pay compensation. In State of Tasmania v Beadle [2001] TASSC 122, 10 Tas R 302 Underwood J (as he then was), with whom Slicer and Evans JJ agreed, said:

"[32] The statute does not require either the notice of injury or the claim for compensation to describe in precise terms the injury suffered. In this respect, the guidance of this Court in Wilkins v St Giles Society A80/1995 is of assistance. In that case, Wright J said with respect to the requirement to give notice of injury that it:

'... need not be stated with the precision of a medical diagnosis but, on the other hand, the essential kind, quality or characteristic of the injury must be disclosed. It will suffice to describe the injury in terms of manifest symptoms so long as the precipitating event is also identified.'

See also Sullivan v The Hobart City Council & Anor [1999] TASSC 101."

1. His Honour agreed, however, that the claim for compensation must be in relation to an identified injury. This follows from various provisions of the Act. For example, s 81(1) provides that an employer's liability to commence making weekly payments only arises when the employer has received "a claim for compensation in relation to an injury".
2. In this case, the injury was identified in the claim form as that which arose from the claimant experiencing severe back pain after he walked away from the battery reach fork on 4 May 2018. This description was sufficient to place the employer on notice as to the basis of its potential liability for compensation. Having identified the injury, the employer's liability to pay compensation then depended on whether that circumstance, the occurrence of pain on 4 May 2018, answered the definition of "injury" in the sense described in s 25(1). It was not necessary for the worker to identify the precise basis of liability under that section. The approved form does not require this level of detail. In fact, the wording of the form directs the worker's attention only to the circumstances in which the existence of the injury became known to the worker. In my view, this requirement for general specification of the circumstances of the relevant injury is sufficient to place the employer on notice as to the injury for which compensation is claimed, and complies with the requirements of the legislation.
3. This degree of notification is consistent with the scheme of the Act. Once the claim has been made and the injury identified, the employer has 84 days after receipt of the claim to dispute liability and refer the matter to the Tribunal under s 81A. If the employer does not dispute liability, then the employer is taken to have accepted liability in respect of that claim: s 81AB. The provisions contained in these sections make it clear that the onus to make the decision as to whether to dispute liability, and if so to provide the material necessary to establish the reasonably arguable case, is on the employer. The period of 84 days is the statutorily accepted period within which the employer must do what is necessary to makes its decision. This provides the opportunity for the employer to determine whether the claimed injury falls within the ambit of s 25. There is nothing in the Act which suggests that the onus of determining such a question, except to state the circumstances in which the injury occurred, is imposed on the worker.
4. The intended operation of the legislation in the manner described is demonstrated by the actions of the respondent in this case. Upon receipt of the claim, the respondent referred the appellant for medical examination and thereby had the opportunity to obtain the medical evidence sufficient to enable it to assess its response to the claim, and to found its argument concerning its dispute of the claim. This medical investigation was directed to examining the cause of the pain experienced on 4 May which led to the allegedly compensable incapacity. The respondent has interpreted that medical advice in a particular manner, and accordingly lodged a dispute. The ultimate question is whether that medical opinion establishes a reasonably arguable case, but the argument must be about whether the incapacity arises from an injury compensable under s 25. The respondent has clearly had ample opportunity to make this assessment and argument, and present evidence in support thereof. There is no reason why the claim should be restricted to one limb only, and such a restriction would be contrary to the scheme of the Act.
5. I also reject the respondent's argument that the claim is defined and constrained by the medical certificate, in particular the boxes ticked by the medical practitioner. The presentation of a medical certificate certifying incapacity is an essential prerequisite to the liability to make weekly payments: ss 34, 69, but that document does not constitute the claim, nor constrain its ambit. A contrary conclusion would be inconsistent with the scheme of the legislation as explained above.
6. In State of Tasmania v Parsons [2002] TASSC 59, 11 Tas R 56, Crawford J, with whom Cox CJ agreed, said:

"[78] However, I respectfully agree with his Honour that s 69(1) did not require a medical certificate to deal with any question of causation. The certificate was required to support only the existence of a total or partial incapacity for work. I agree that the words 'the existence of such total or partial incapacity' in the subsection should not be interpreted as meaning the existence of a total or partial incapacity for work that results from any injury suffered by a worker. The ordinary, natural and grammatical meaning of the words does not suggest such an interpretation. Further, the legislature could hardly have expected a medical practitioner, in the usual case, to be able to certify that a particular incapacity was caused by a particular injury that almost certainly, the practitioner did not witness. At best, all the practitioner could certify would be that the incapacity was consistent with having resulted from a particular injury claimed to have occurred by the worker. The subsection certainly did not provide for that."

1. I agree with these observations. The purpose of the medical certificate is to certify the requisite incapacity. The Act does not require certification as to causation, nor does it confer any other role on the certificate in defining or constraining the claim. The claim made by the worker must identify the injury for which it is made. All consequential questions of liability and causation are then determined pursuant to the assessment process set out in the legislation, which includes s 81A.
2. Accordingly, I am satisfied that, in this case, the claim for compensation was made in respect of an injury, which was the pain suffered by the appellant on 4 May 2018. The respondent's dispute under s 81A depended on it establishing a reasonably arguable case concerning its liability to pay compensation. The reasonably arguable case needed to relate to whether such an injury had occurred and if so, whether it fell within the ambit of s 25(1). This, in turn, involved questions of liability and causation.

1. It is clear from Mr Dohrmann's reports that his opinion is that the appellant did not suffer an injury in the primary sense (s 25(1)(a)) on 4 May 2018. The respondent argued that comments contained in the first report suggest that it was at least claimed by the appellant that there had been such an injury. I disagree. In my view, there is no basis for this interpretation of Mr Dohrmann's comments. In the first report, he expressly states that his opinion is that the appellant suffered "an injury taking the form of an aggravation of pre-existing lumbar spondylosis which occurred in the course of his employment on 4 May 2018". When this comment is read in the context of the whole of that report, it is clear that his opinion is that the symptoms experienced by the appellant on 4 May arose from an aggravation of the underlying condition of lumbar spondylosis. This view is confirmed in his second report, when he states "it is reasonable to conclude that there was no specific incident or accident and therefore no particular event or activity that caused injury on 4.5.2018".
2. Mr Dohrmann's opinion is that the appellant had, for many years, suffered from the condition of lumbar spondylosis. This condition clearly comes within the definition of "disease", and hence would constitute an injury pursuant to s 25(1)(b). However, to be compensable under that provision, it is also necessary to establish that the appellant's employment contributed to the appellant suffering that injury to a substantial degree, which means that the employment must have been the major or most significant factor.
3. Section 3(5) provides that for the purposes of the Act, where the worker suffers an injury that is a disease, that injury shall be deemed to have occurred:

(a) on the day on which the worker became totally or partially incapacitated by reason of that injury; or

(b) if a day cannot be ascertained under par (a), on the day on which a medical practitioner has certified that the worker was first incapacitated by reason of that injury.

1. There is no evidence that the appellant had suffered total or partial incapacity for work by reason of the underlying condition of lumbar spondylosis prior to 4 May 2018. Given that a medical practitioner has certified incapacity as from that date as a result of the underlying condition of back pain, s 3(5) operates to deem the injury (the disease) to have occurred on that date. This is the only reasonable conclusion available from the combination of Mr Dohrmann's evidence and the other evidence, including the medical certificates.
2. Mr Dohrmann does not suggest that the underlying condition of lumbar spondylosis was caused by the worker's employment. It is a naturally occurring degenerative condition. He opines that employment has contributed to the development of the disease over a number of years, but it is reasonably arguable on the basis of his opinion that employment is not the major or most significant factor contributing to the underlying disease. At the very least, the natural degenerative process must be open as an alternative explanation.
3. However, the extended definition of injury must also be considered. As already noted, the only reasonable conclusion from Mr Dohrmann's reports is that the pain experienced by the appellant on 4 May which resulted in incapacity in fact arose from an aggravation or exacerbation of the underlying disease. This conclusion is consistent with authority as to the meaning and operation of the extended definition. In Long v Kmart Australia Ltd (above), Porter J considered in some detail the interaction between the extended definition and s 25(1). The following observations can be extracted from his Honour's judgment:
   • That the substantives are not synonymous with each other, nor are they mutually exclusive. They "have different shades of meaning and there is overlap between at least some of them": [43]. In general terms, the occurrence of one or more of the substantives is a question of fact and "the answer depends on whether for the sufferer the consequences of the affliction have become more serious": [48].
   • There is a relevant aggravation if the symptoms and difficulties emanating from it have increased or become more serious: [50].
   • "The word 'exacerbate' involves the concept of the heightening of the effect upon an individual as where his sufferings increase. There is an exacerbation of disease where the experience of the disease by the patient is increased or intensified by an increase or intensifying of symptoms. The word is directed to the individual and the effect of the disease upon him rather than being concerned with the underlying mechanism": per Moffat J in Semlitch v Federal Broom Co Pty Ltd (1964) 80 WN (NSW) 1603, cited with approval by Kitto J in Federal Broom Company Pty Ltd v Semlitch [1964] HCA 34; (1964) 110 CLR 626 at 634.
4. The only reasonable conclusion available on the evidence, including Mr Dohrmann's reports, is that the incapacity which arose on 4 May 2018 resulted from the appellant's experience of symptoms on that day after having worked on the reach fork, and that those symptoms constituted an aggravation or exacerbation of the underlying lumbar degenerative condition. It is clear that the effect of the underlying condition on him was increased or intensified by these symptoms. On the basis of Mr Dohrmann's evidence, there is no room for any other explanation of the incapacity.
5. The respondent relies on boxes ticked by Dr Jackson in the initial medical certificate as expressing an opinion that incapacity has resulted from an injury in the primary sense which occurred on 4 May. However, a proper reading of the medical certificate does not support that conclusion. The ticked box that states "an incident which occurred on 4 May 2018" is preceded by the words "The above named worker has stated the condition to be caused by". The doctor then goes on to describe the circumstances as stated by the appellant. It is evident that these words are not an expression of opinion by Dr Jackson, but simply his record of what he was told by the appellant. This description includes the further words, "In the course of driving a fork lift to pick up ... he twisted to the right." This version of the appellant is entirely consistent with the description of the events of the day which led up to the relevant experience of pain, as explained by the appellant to Mr Dohrmann.
6. Dr Jackson has also ticked a box which expresses the following:

"If known, the injury or disease is ... a new condition".

However, in considering the effect of the opinion conveyed by this statement, the other available alternative descriptors are instructive. They are:

• The recurrence of a previously compensable condition.
• An aggravation of an existing condition.

1. While the relevant question does call for the expression of opinion by the author of the certificate, the meaning of that opinion so expressed is equivocal, in respect of the legislative requirements for the liability to pay compensation. The alternatives expressed above do not correlate to the requisite causal requirements specified in the legislation. A "new condition" has no relevant meaning in that sense. It could mean an injury in the primary sense under s 25(1)(a), but it could also bear other meanings. For example, it might simply mean a condition which had not resulted in a compensable incapacity previously. Given that another alternative descriptor is the recurrence of a "previously compensable" injury, this interpretation is more than feasible. In any event, as was noted by Crawford J in State of Tasmania v Parsons (above), the purpose of the certificate is to certify incapacity, not to deal with causation. It is true that Dr Jackson had been treating the appellant prior to 4 May 2018 in relation to his back problems. However, without more, it is impossible to derive a concluded and relevant opinion about the nature of the injury and its causation from the contents of the medical certificate. The respondent could have obtained written evidence from Dr Jackson, or called him to give oral evidence at the hearing with respect to these matters, but did not do so. As already noted, the onus is on the employer to establish a reasonably arguable case. In my view, the certificate does not provide any support for the argument that the appellant suffered an injury in the primary sense on the relevant day.
2. It follows that the only reasonable conclusion available from the evidence before the Commissioner was that the incapacity arose from an aggravation or exacerbation of the underlying disease. This is an injury within the relevant definition. However, liability on the part of the respondent to pay compensation for that injury depended on the existence of the requisite causal relationship between the employment and the injury.

1. In Long v Kmart Australia Ltd, Porter J considered the interrelationship between s 25(1)(b) and the extended definition of "injury" in s 3. His conclusion, expressed at [52], is that in the case of an aggravation, exacerbation, etc of a pre-existing disease, the injury will fall within s 25(1)(b) if the employment was the major or most significant contributing factor to that aggravation, exacerbation, etc. The causative requirement, therefore, relates to the aggravation or exacerbation of the underlying disease, not the development of the disease itself.
2. Accordingly, the question for the Commissioner was whether the evidence permitted a reasonable argument that the appellant's employment was not the major or most significant factor in the causation of the aggravation or exacerbation of the underlying disease. In the circumstances of this case, that question really came down to whether the evidence permitted a reasonable argument that there were other possible causes of the appellant's pain as he experienced it on 4 May, other than his employment, which might qualify as the major or most significant factor.
3. It is apparent from the Commissioner's brief reasons that she did consider this question, but confined that consideration to whether the aggravation or exacerbation had arisen because of work related circumstances, such as a specific incident, insult or process which had taken place on 4 May. In doing so, she accepted the respondent's counsel's argument that the question was so confined. I am satisfied that in restricting her consideration of the requisite causal link in this way, the learned Commissioner was in error.
4. There is little doubt that it was arguable that the symptoms did not arise from a specific incident or insult on 4 May. The effect of Mr Dohrmann's second report was that it was not possible to identify a specific incident or additional insult or process, or specific pathological change on 4 May 2018, as the cause of the symptoms which had led to incapacity on that day. However, none of those circumstances was an essential prerequisite to the respondent's liability to pay compensation. A temporal connection between employment and the underlying process which led to the increase in symptoms on 4 May was not necessary. As Porter J said in Long v Kmart Australia (above) at [78]:

"The test does not require an 'aggravation' to occur, commence or conclude in the course of the employment. The question is simply whether there has been an 'aggravation' of a pre-existing disease, and whether the employment has the requisite degree of causal connection."

1. The Commissioner misstated and misapplied this test. It is clear from her brief reasons that she was looking for events on 4 May which had both a causal and temporal connection with the aggravation or recurrence. This was not necessary. The Commissioner's misunderstanding of the legislative test is a classic error of law.
2. The Commissioner's confusion and consequent error was contributed to by the answers in Mr Dohrmann's second report. At the hearing, the respondent had relied particularly on Mr Dohrmann's comment that the appellant appeared "not to have suffered a specific work-related injury on 04.05.2018."
3. However, this and other comments to similar effect must be read in the context of the questions asked by the respondent's lawyer in the letter to which that report was responsive. These questions focussed his attention on the causal effect of work conducted on 4 May 2018. In this sense, they were unintentionally misleading. For example:
   • In Mr Dohrmann's answer that there was no specific incident or accident and therefor no particular event or activity that caused the injury on 4 May 2018, he was responding to a question which stated as follows:

"I ask you to concentrate on what had occurred on 4 May 2018 and whether what had occurred on that day can be regarded as substantially caused by work related activity or events."

• At point 9 in the letter, Mr Dohrmann was asked whether "there was any evidence of any pathological change occurring on 4 May 2018". He responded in the negative, but added, "though there was clearly a significant increase in symptoms from that date".

1. In my view, nothing said by Mr Dohrmann in the second report changed the effect of the opinion expressed in his first report. The questions in the letter focused on a temporal causal relationship between employment activities on 4 May and the reported injury. As I have already explained, this temporal connection was irrelevant to the actual requirements of the legislation. Mr Dohrmann consistently maintained that the appellant had suffered incapacity as a result of his symptoms experienced on 4 May and that there was a causal relationship between those symptoms and his employment generally. The Commissioner ought to have concentrated on the nature and extent of that causal relationship without unduly confining that question to the employment activities being conducted on 4 May.
2. This conclusion is sufficient to establish a ground of appeal (ground 2). The consequence of the error is that the Commissioner has misstated the statutory test applicable to the liability of the respondent to pay compensation. This necessarily invalidates her conclusion as to the existence of a reasonably arguable case about that issue. The question which then arises is what consequence should follow from this conclusion.
3. It will be clear from what I have already written that the remaining critical question with respect to the respondent's liability to pay compensation relates to the sufficiency of the causal relationship between employment and the aggravation or exacerbation of the underlying disease. My powers on this appeal include giving or making any judgment which I consider should have been given or made by the Tribunal (see rr 693 and 703 of the Supreme Court Rules 2000). The evidence before the Tribunal consisted solely of the documentation described above. I am, therefore, in as good a position as the Commissioner to determine whether that material establishes a reasonably arguable case, in particular with respect to the question of causation. I will, accordingly, now give consideration to that question.

1. As has already been noted, the requisite causal relationship is that the appellant's employment was the major or most significant contributing factor to the aggravation or exacerbation. The use of the definite article in this legislative formulation is important. Section 3(2A) was introduced by an amendment in 1995 (16/1995) in response to the decision of the Full Court in University of Tasmania v Cane [1994] TASSC 73; (1994) 4 Tas R 156. That case had dealt with the previous formulation of s 25(1)(b), which provided that compensation was payable to a worker who "suffers an injury, which is a disease, arising out of and in the course of his employment and to which his employment has contributed to a substantial degree". The extended definition of injury had not then been inserted into the Act. The effect of that decision was that the required causal contribution of the employment to the disease must be "substantial" which was to be assessed in a relative sense and required only that the work related cause be "more than trivial or inconsequential". This formulation of the test was applied by Zeeman J in Attorney-General v Smith [1994] TASSC 138. In the second reading speech of the Bill which inserted s 3(2A), the Minister, Mr Groom, made it abundantly clear that the amendment was in response to this judicial interpretation and that the intention was to establish the requirement for the employment to be the principal contributing factor to the disease. The provision was further amended by No 99 of 2000, by inserting the word "only" before the words "if it is the major or most significant factor", thereby establishing without doubt the necessity for employment to be the predominant contributing factor to the disease, or the aggravation or exacerbation of the disease, if the injury is to fall within s 25(1).
2. The appellant argues that the only reasonable conclusion available from the whole of Mr Dohrmann's opinion is that the appellant's employment fulfils this requirement. The appellant points to the temporal link between his work on the reach fork and his experience of symptoms, and Mr Dohrmann's expressions of opinion, including the statement made in his report that, after considering the definition in the Tasmanian legislation, he considered that the appellant "has suffered an injury in this context".
3. The respondent relies heavily on the comment made by Mr Dohrmann in the same paragraph which concludes with the sentence: "It is in this respect that I believe that a reasonable argument can be made that his employment has been a major contributing factor to the aggravation of lumber spondylosis from which he now suffers." [The italics are mine.] The respondent relies on Mr Dohrmann's use of the indefinite article. A finding that employment was a major contributing factor to the aggravation would not be sufficient to make the injury compensable within s 25(1) and the extended definition.
4. This argument reintroduces consideration of what is meant by "a reasonably arguable case ... concerning the liability of the employer to pay compensation". In this case, on the material adduced by the employer, Mr Dohrmann has opined that the appellant has suffered an injury in the context of the relevant definition which includes the aspect of causation. The respondent, however, seeks to rely on other comments by the neurosurgeon which suggest the possibility that his opinion may not reach the level of causation required to make the injury compensable, in particular his use of the words "a major contributing factor", as opposed to "the major or most significant contributing factor". However, while Mr Dohrmann's comments in his reports are somewhat equivocal, no attempt was made by the respondent to adduce further explanation from him, either orally or in writing. The question is whether the possibilities left open by this equivocation amount to "a reasonably arguable case".
5. In St Helens Oysters Pty Ltd v Coatsworth (above), Evans J said of this requirement:

"The very notion of a 'reasonably arguable case' like the very notion of a 'prima facie case', precludes a final determination of a disputed question of fact. See North Ganalanja (supra) at 639. On the face of s81A, a reasonably arguable case will exist concerning the liability of an employer to pay a worker if it is reasonably arguable on the material available in relation to the claim or identified deficiencies or weaknesses in the claim that, following a contested hearing it may be rejected."

1. In this case, although Mr Dohrmann expresses the opinion that employment was causally related to the development of the disease, he does not directly and squarely deal with the question of whether it is "the major or most significant contributing factor" in respect of the aggravation or exacerbation experienced by the appellant on 4 May. On one interpretation of his reports, it can be inferred that he was expressing a view that would result in the injury being compensable, that is that employment was the major or most significant factor. However, in my view, it is also open to conclude that he would not attribute to the employment this level of contribution, notwithstanding that it was a major contributing factor. It is implicit in his opinion as to the nature of the underlying disease that natural progression may also have played a role in the onset of symptoms on 4 May. This may well explain his choice of words. On a hearing, the resolution of this question of causation will involve a determination of fact, on the basis of "a common sense evaluation of the causal chain": Kooragang Cement Pty Ltd v Bates (1994) 35 NSWLR 452, cited by Pearce J in Vos Constructions v Norton-Smith. Accordingly, I am satisfied that, on the evidence before the Tribunal, a reasonably arguable case exists concerning the liability of the respondent to pay compensation. This is because Mr Dohrmann's reports leave open a reasonable possibility that following a contested hearing, the claim may be rejected, particularly having regard to the requirement that the employment is the major or most significant factor in the aggravation or exacerbation of the underlying disease. This reasoning is consistent with that employed by Evans J in St Helens Oysters Pty Ltd v Coatsworth where his Honour said at [14]:

"As already explained in relation to the first ground for disputing liability, on the limited information before the learned Commissioner, it was not possible to determine what role the worker's employment played in his disease. Of necessity this means that it was not possible to determine whether such role as his employment played arose substantially from its termination. In these circumstances, on the limited material before the learned Commissioner, there was a reasonably arguable case that the employer could rely on s25(1A)(c) to avoid liability to the worker."

1. It follows that although the Commissioner erred in point of law in her reasons for finding that there was a reasonably arguable case, had she correctly determined and applied the law, she would inevitably have reached the same conclusion. In those circumstances, the only appropriate outcome is that the appeal must be dismissed. That is the order I make.