Secretary, New South Wales Department of Education v Johnson

The Statutory Scheme

1. Section 9 of Compensation Act relevantly provides that a worker who has received an injury is to receive compensation from the worker's employer in accordance with the Compensation Act. Under s 4(1), injury means, relevantly, personal injury arising out of or in the course of employment. Under s 9A(1), however, no compensation is payable under the Compensation Act in respect of an injury unless the employment concerned was a substantial contributing factor to the injury.
2. Section 66 of the Compensation Act relevantly provides that a worker who receives an injury that results in a degree of permanent impairment greater than 10% is entitled to receive compensation for that permanent impairment from the worker's employer. Only one claim can be made under the Compensation Act for permanent impairment compensation in respect of the permanent impairment that results from an injury. Section 66(2) sets out the method whereby the amount of permanent impairment compensation is to be calculated according to the degree of permanent impairment suffered by a worker.
3. Section 65A of the Compensation Act provides for impairment arising from psychological and psychiatric injuries to be assessed separately from impairment arising from physical injury. An approved medical specialist may decline to make an assessment of the degree of permanent impairment of an injured worker until the approved medical specialist is satisfied that the impairment is permanent and that the degree of permanent impairment is fully ascertainable.
4. Part 7 of Ch 7 of the Management Act, which consists of ss 319 to 331 inclusive, deals with "Medical Assessment" in relation to medical disputes concerning entitlement to compensation. Under s 319, medical dispute means, relevantly, a dispute between a claimant and the person on whom a claim is made about the degree of permanent impairment of a worker as a result of an injury. Under s 322, impairments that result from the same injury and impairments that result from more than one injury arising out of the same incident are to be assessed together. Under s 322A, only one assessment may be made of the degree of permanent impairment of an injured worker.
5. The medical assessment certificate that is given in connection with an assessment is the only medical assessment certificate that can be used in connection with any further or subsequent medical dispute about the degree of permanent impairment of the worker as a result of the injury concerned (whether the subsequent or further dispute is in connection with a claim for permanent impairment compensation, the commutation of a liability for compensation or a claim for work injury damages). Accordingly, a medical dispute about the degree of permanent impairment of a worker as a result of an injury cannot be referred for, or be the subject of, assessment, if a medical dispute about that matter has already been the subject of assessment and a medical assessment certificate.
6. Section 322(1) of the Management Act relevantly provides that the assessment of the degree of permanent impairment of an injured worker for the purposes of the Compensation Act is to be made in accordance with the NSW Workers Compensation Guidelines for the Evaluation of Permanent Impairment (the Guidelines). The Guidelines may make provision for or with respect to the determination of a deduction required by s 323.
7. Section 323(1) of the Management Act relevantly provides that, in assessing the degree of permanent impairment resulting from an injury, there is to be a deduction for any proportion of the impairment that is due to any previous injury. Under s 323(2), if the extent of a deduction under s 323 would be difficult or costly to determine, it is to be assumed that the deduction is 10% of the impairment, unless that assumption is at odds with the available evidence. The reference to medical evidence is a reference to medical evidence accepted or preferred by the approved medical specialist in connection with the medical assessment of the matter. None of the Compensation Act, the Management Act or the Guidelines expressly provides for, or excludes, apportionment where there is an injury subsequent to the injury that is the subject of a claim.
8. Under s 325(1) of the Management Act, the approved medical specialist to whom a medical dispute is referred is required to give a medical assessment certificate as to the matters referred for assessment. A medical assessment certificate is to set out details of the matters referred for assessment, certify as to the assessment with respect to those matters, set out the reasons for that assessment and set out the facts on which the assessment is based. Under s 326(1)(a), an assessment certified in a medical assessment certificate pursuant to a medical assessment under Pt 7 of Ch 7 is conclusively presumed to be correct as to the degree of permanent impairment of a worker as the result of an injury and under s 326(1)(b) as to whether any proportion of permanent impairment is due to any previous injury or pre-existing condition or abnormality.
9. Thus, the effect of ss 319 and 326 is that an authorised medical specialist or the Appeal Panel must assess the degree of permanent impairment of the person as a result of an injury. Not only must the employment be a substantial contributing factor to the injury, but the impairment must also be the result of the injury. That is to say, it must be possible to demonstrate that there is a causal connection between the compensable injury and the impairment.

The Medical Dispute

1. The Worker sustained the First Injury when she was abused, threatened and physically assaulted by a student on 30 April 2014. On 3 August 2016, her solicitor served a notice of claim on the Secretary claiming lump sum compensation under s 66 of the Compensation Act. On 21 December 2016, the Secretary gave notice disputing liability for lump sum compensation. On 10 March 2017, the Worker lodged with the Commission an application to resolve the dispute between her and the Secretary as to her entitlement to lump sum compensation (the Application).
2. The Application was supported by statements made by the Worker to the NSW Police Force in relation to the assault that gave rise to the First Injury, in which she said that the assault occurred on the third day of her employment at Fairvale High School. The Application was also supported by various medical assessments, including a report by Dr Ben Teoh of 10 July 2016 expressing the opinion that the Worker's whole person impairment as a result of the First Injury was 17%. The Secretary filed a reply to the Application (the Reply) confirming the existence of the dispute as stated in the notice of 21 December 2016. The Reply was supported by a report dated 9 November 2016 from Associate Professor Kaplan expressing the opinion that the adjustment disorder suffered by the Worker from the First Injury had resolved but that the Worker would benefit from counselling to help her deal with secondary issues arising from the First Injury and not related directly to her claim. Professor Kaplan also expressed the opinion that, since the Worker had current capacity for a 35 hour week and was recently employed full time as a hostel manager with Hostels, she could return to full pre-injury duties. Finally, Professor Kaplan expressed the opinion that the Worker had not sustained any whole person impairment from the First Injury.
3. There was no material before this Court to explain why there was a delay between the time of the First Injury, on 30 April 2014, and the Worker's application to the Commission to resolve the medical dispute, lodged on 10 March 2017, only three weeks before the Second Injury. In an ideal world, the assessment of the Worker's permanent impairment resulting from the First Injury would have been undertaken by the AMS and the Appeal Panel prior to the intervention of the Second Injury. However, for whatever reason, it was not. The consequence is the difficult exercise that was necessarily undertaken by the AMS and the Appeal Panel, as explained below.

Certificates of the AMS

1. The second respondent, the Registrar of the Commission (the Registrar) referred to the AMS the medical dispute that was the subject of the Application and the Reply. On 9 June 2017, the AMS provided a medical assessment certificate in which the Worker was assessed as suffering from a whole person impairment of 19% as a result of the First Injury (the First AMS Certificate). On 3 July 2017, the Secretary lodged an appeal against the decision of the AMS. Under s 327(1) of the Management Act, a party to a medical dispute may appeal against a medical assessment under Part 7, but only in respect of a matter that is appealable under s 327 and only on the grounds for appeal under s 327. Under s 327, a matter is appealable if it is a matter as to which the assessment of an approved medical specialist certified in a medical assessment certificate under Part 7 is conclusively presumed to be correct in proceedings before a court or the Commission. Section 327(3) specifies the only grounds for appeal.
2. An appeal is to be made by application to the Registrar. However, an appeal is not to proceed unless the Registrar is satisfied that, on the face of the application and any submissions made to the Registrar, at least one of the grounds for appeal specified in s 327(3) has been made out. On 20 September 2017, a delegate of the Registrar decided, under s 327, that he was not satisfied that any of the grounds of appeal sought to be relied on by the Secretary had been made out.
3. On 21 September 2017, the Secretary requested particulars from the Worker of her employment activities since 1 September 2016. On 9 October 2017, the Worker responded to the request, indicating that she had lodged with Comcare, the workers compensation insurer of Hostels, a claim for workers compensation in respect of the Second Injury.
4. In fact, on or about 26 April 2017, the Worker had lodged a claim form with Comcare seeking worker's compensation in respect of the Second Injury. In that form, the Worker stated that she had suffered bullying, sexual harassment and threats of physical violence while at her workplace with Hostels and that she first sought medical treatment on 30 March 2017, from Dr Tarannum Rahman, her treating doctor. She also stated in the form that she had not experienced a similar symptom, injury or illness, work-related or otherwise, and had not claimed compensation for similar injury or condition. The claim form was accompanied by a certificate from Dr Rahman dated 30 March 2017 certifying that the Worker would be unfit for work from 30 March 2017 to 5 April 2017. Dr Rahman subsequently provided certificates that the Worker had been diagnosed with adjustment disorder with mixed anxiety and depressed mood.
5. The Secretary subsequently pointed out to the Registrar that it appeared that the Worker had sustained the Second Injury after lodgement of the Application but before her examination by the AMS, with the result that the AMS made no reference to the Second Injury in the First AMS Certificate. On 5 February 2018 the Registrar referred the medical dispute back to the AMS for further assessment in the light of that additional information, pursuant to s 329(1)(b) of the Management Act.
6. The AMS provided a further medical assessment certificate on 11 April 2018, certifying that the whole person impairment of the Worker by reason of her psychiatric or psychological condition suffered on 30 April 2014 was 17% (the Second AMS Certificate). After setting out, in his reasons for issuing the Second AMS Certificate, the history that had been given by the Worker following the First Injury, the AMS recorded that he had obtained a "more detailed and nuanced account" of events from the Worker. The AMS recorded that, in August 2016, the Worker had obtained a position as hostel manager with Hostels, which was terminated after she had a "blow up" with the Chief Executive Officer of Hostels.
7. The AMS referred to the opinion of Dr Rahman, the Worker's treating doctor, that her current condition was not an aggravation of a pre-existing or underlying condition and that her current mood disorder was related to the events that were taking place at work with Hostels, which had made her feel uncomfortable. The AMS referred to a medical opinion by Dr Takyar that the Worker had reported that she had been diagnosed in 2014 "in the context of an event but she did not disclose what the circumstances were". The AMS also referred to a report by Dr Chow that the Worker had been assaulted by a student while working for the Secretary in 2014 and subsequently lodged a claim. The AMS recorded that Dr Chow had noted that the Worker was on a "workers compensation claim and was diagnosed with post-traumatic stress disorder" and that she had said that, after 12 months of treatment, she had recovered from the condition and had since been working in a new workplace. The AMS recorded that both Dr Chow and Dr Takyar, as well as Dr Rahman, had diagnosed an adjustment disorder. The AMS then commented that the Worker "disputes the accuracy of these statements". It is not entirely clear as to the statements to which the AMS was referring in making that comment.
8. The reasons of the AMS then recorded that the Worker had indicated that she remained distressed by psychiatric symptoms between the time when she ceased working with the Secretary and the time when she commenced duties with Hostels. He recorded that the Worker claimed that, on the day when she started working with Hostels, she had felt "pretty much the same as I always had" and that she only commenced duties because she "had to look for jobs". The AMS said that she told him that she had been pressured back into employment but that she was no better than the day when she "went off".
9. The AMS then recorded that the Worker had indicated that she had commenced duties with Hostels but that, because of poor performance arising from interpersonal difficulties and the ongoing effects of her psychological injury, she was spoken to in a gruff and disagreeable manner by the Chief Executive Officer of Hostels and developed "symptomatic intensification". The AMS recorded that, after her employment by Hostels was terminated, the Worker litigated the matter with Hostels in the Fair Work Commission and was reinstated in early December 2016, having been found to have been the victim of an unfair dismissal.
10. The AMS recorded that the Worker told him that she had been "affronted by a subsequent incident" involving one of the residents of the hostel that she was managing for Hostels, which included aggressive behaviour and threats to kill her. She told the AMS that she suffered further "symptomatic intensification" and ceased duties on 24 March 2017. The AMS recorded that the Worker indicated that "she continues to isolate and remained socially disengaged" and that she suffered "ongoing symptoms of post-traumatic stress disorder".
11. In his summary of his reasons for the Second AMS Certificate, the AMS said that, having had the opportunity of reviewing additional information and re-examination of the Worker, he remained of the view that she presented with "a persisting or chronic post-traumatic stress disorder" that "in all probability was exacerbated in the subsequent employment with [Hostels]". The AMS stated that the Worker's history, as reported "across multiple examiners at different points, was inconsistent and unreliable." He said that, while he did not observe any evidence that the Worker was dissimulating or over-reporting her symptoms, and her clinical presentation was overall genuine, the narrated history was often "lacking in detail", particularly as to previous events. He noted that Dr Chow and Dr Takyar had been given deficient or inaccurate histories of the First Injury and that the Worker had not described in any substantive manner the subsequent triggering of her symptoms.
12. The AMS then said the following: "Applying the principle of charity, [the Worker]'s apparent problems narrating her history is a function of her psychiatric symptoms rather than any intent to mislead. What is clearly evident is that [the Worker] developed a psychological injury in the course of her duties with [the Secretary] that manifest as chronic post-traumatic stress disorder that was evident at my previous examination. What is now clear is that the injury was exacerbated by subsequent deployment with [Hostels] and that some of the observed level of WPI (unchanged since my last assessment) must be attributed to the presumed exacerbating effects of this."
13. The AMS ended his reasons by saying that, given the problems with history and the Worker's incapacity to narrate a clear account of the effects of that history, the only acceptable methodology would be a deduction of 1/10th of the observed whole person impairment. He certified that the whole person impairment of the Worker was 17%, saying that, in making that assessment, he had made a 1/10th deduction for the effects of the Second Injury. He described the deduction of 1/10th as being pursuant to s 323 "for pre-existing injury, condition or abnormality". The whole person impairment of the Worker before deducting 10%, as assessed by the AMS, was 19%. There is no challenge to that assessment by the Secretary. However, it is common ground that the AMS erred in deducting 10% on the basis of s 323, since s 323 applies only to a pre-existing condition and not to a subsequent condition.

The Appeal Panel's Decision

1. At the request of the Secretary, the medical dispute between the Secretary and the Worker was referred to the Appeal Panel on the basis that the Second AMS Certificate contained a demonstrable error, being the erroneous application of s 323 of the Management Act to the assessment of the Worker's permanent impairment as a result of the First Injury. While the Appeal Panel received fresh evidence, it determined that it was not necessary for the Worker to undergo a further medical examination.
2. For reasons published on 18 July 2018, the Appeal Panel determined that the Second AMS Certificate should be revoked and that a new medical assessment certificate should be issued. In its reasons of 18 July 2018, the Appeal Panel said that it was satisfied that the AMS had fallen into error in making a 10% deduction pursuant to s 323 of the Management Act in respect of the Second Injury. The Appeal Panel then considered the question of "apportionment" of the Worker's permanent impairment between the First Injury and the Second Injury. It recorded that there was no dispute that, as result of the assault in the course of her employment by the Secretary, the Worker had suffered a psychological injury and had been diagnosed as suffering from a post-traumatic stress disorder, or an adjustment disorder, with mixed depressed and anxious mood. The Appeal Panel then referred to assessments made by other medical practitioners and the histories obtained by those medical practitioners from the Worker.
3. The Appeal Panel found that, when first examined by the AMS, the Worker failed to disclose the nature and extent of her psychological injury while employed by Hostels and that the history that she provided to the AMS was not accurate. The Appeal Panel then referred to the claim form submitted by the Worker to Comcare in April 2017 in relation to the Second Injury, in which she alleged that she had suffered an injury due to bullying, harassment, intimidation, threats of violence, sexual harassment and threats of physical violence and denied having ever suffered similar symptoms, injuries or illnesses. The Appeal Panel characterised the failure to disclose those matters to the AMS as "incorrect and misleading".
4. The Appeal Panel recorded that, when the Worker was questioned by the AMS about the Second Injury, she merely disputed the accuracy of the histories recorded by the other medical practitioners and claimed that she continued to have symptoms after leaving the employ of the Secretary and felt much the same as she always had. The Appeal Panel referred to the acknowledgement by the AMS that the Worker's history was inconsistent, unreliable and at times lacking in detail and his acceptance, without question, the evidence given by the Worker that the histories given to the other medical practitioners were deficient or inaccurate. The Appeal Panel observed that the AMS had commented that the inconsistency in the history was a function of the psychiatric symptoms of the Worker rather than any intent to mislead. The Appeal Panel said, however, that it did not hold the same view because the histories recorded by different assessing medical practitioners appeared to be consistently inconsistent with the attribution of the Worker's condition to one or other injury depending upon the context of the assessment.
5. The Appeal Panel also observed that the AMS did not question the Worker about the accuracy of the history recorded by her treating medical practitioner, who the Appeal Panel considered would have had an intimate knowledge of all of the Worker's psychological injuries. The Appeal Panel concluded that, whilst it was conceivable that one medical practitioner may have recorded an incorrect history, it was highly unlikely that three medical practitioners would have made the very same error. The Appeal Panel considered that the evidence showed that the Worker was an "unreliable historian" and that the differences in the histories were significant without an adequate explanation forthcoming from her.
6. The Appeal Panel considered that it was open to the AMS to assess the degree of the Worker's whole person impairment in the manner that he did and that no error on his part was disclosed in that regard. The Appeal Panel was satisfied that the Worker had been properly assessed as having 19% whole person impairment "as a result of the cumulative effect of [her] two work injuries". However, the Appeal Panel considered that the AMS had fallen into error in relation to the assessment of the impact of the Second Injury on the Worker's mental state and in concluding that the Worker's difficulty in relation to a correct history was due to her psychiatric symptoms rather than any intent to mislead. The Appeal Panel considered that the Worker's evidence was unreliable and, accordingly, was not satisfied that the AMS had properly applied his clinical judgment or had provided adequate reasons for his assessment. The Appeal Panel concluded that the AMS's conclusion was compromised by the Worker's unreliable and inaccurate history, which the Appeal Panel considered to be of little probative value.
7. The Appeal Panel concluded that the Worker suffered a psychological injury as a result of what it characterised as "a minor assault" and that, while that injury was incapacitating, the Worker was subsequently able to secure employment with Hostels, where she worked for 10 months and was employed in "a far more confronting position". The Appeal Panel observed that the Worker had interpersonal issues with the Chief Executive Officer of Hostels and that her services were terminated because she stood up for herself and not because she was suffering from any chronic psychological disorder. The Appeal Panel noted that the Worker was mentally strong enough to initiate legal proceedings in the Fair Work Commission, where she succeeded in her claim of unfair dismissal and was reinstated. The Appeal Panel found that the Worker eventually ceased work in March 2017 and was certified as unfit by her own medical practitioner as a consequence of being exposed to highly traumatic events while employed by Hostels comprising aggressive behaviour and threats to her life. The Appeal Panel considered that the number and nature of the events and the degree of threat to the Worker at Hostels were far greater than those that she experienced with the Secretary.
8. The Appeal Panel concluded that the First Injury contributed only "a minority of the level of [the Worker's] whole person impairment" when compared with the "significant traumatic psychological injury" sustained by her in the employ of Hostels in early 2017. The Appeal Panel was satisfied that the First Injury contributed at most one third to the degree of her whole person impairment, being 6%. The Appeal Panel therefore revoked the Second AMS Certificate and authorised the issue of a new AMS Certificate. In pursuance of that decision, the Appeal Panel issued a medical assessment certificate of 18 July 2018 certifying that the total whole person impairment of the Worker as a result of the First Injury was 6%.

Proceedings before the Primary Judge

1. By summons filed on 17 October 2018, the Worker sought orders under s 69 of the Supreme Court Act 1970 (NSW) that the decision of the Appeal Panel on 18 July 2018 be quashed and the matter be remitted to a differently constituted medical appeal panel for determination according to law. That relief was claimed on the basis that: 1. the determination that the Second AMS Certificate contained a demonstrable error resulted from an error of law on the face of the record or constituted jurisdictional error, and 2. the medical assessment certificate of 18 July 2018 itself contained jurisdictional error or an error of law on the face of the record in reassessing the Worker's whole person impairment. The Registrar was the first defendant, the Appeal Panel was the second defendant and the Secretary was the third defendant.
2. Two issues were raised before the primary judge. The first issue was decided favourably to the Secretary and that question is not before this Court. His Honour formulated the second question [1] as being whether the Appeal Panel failed to identify the relevant legal principle applicable to the task upon which it was engaged in undertaking the reassessment of the Worker's whole person impairment.
3. The primary judge recorded the Worker's contention that she simply had to demonstrate that her permanent impairment resulted from, or was materially contributed to by, the First Injury. She contended that the Appeal Panel, contrary to legal principle, had undertaken an apportionment exercise and erroneously determined that the First Injury caused about one-third of her impairment and the Second Injury accounted for about two-thirds of her impairment. The Secretary, on the other hand, contended that it was open to, and appropriate for, the Appeal Panel to determine the whole person impairment attributable to the First Injury in the manner in which it did because the relevant provisions of the Management Act required an authorised medical specialist or a medical appeal panel to assess the degree of permanent impairment of a worker that resulted from an injury. That is to say, the statutory task of finding a causal link between the First Injury and the permanent impairment included the task of apportionment upon which the Appeal Panel correctly embarked and which it completed, resulting in the certificate of 18 July 2018.
4. The primary judge observed that at no time did the Appeal Panel depart from the diagnosis of the Worker's condition or the extent of the assessment made by the AMS of her permanent impairment. Rather, his Honour said, the Appeal Panel considered the question of apportionment between the First Injury and the Second Injury. His Honour observed that the Appeal Panel's ultimate determination was the end result of its consideration and determination of that question.
5. The primary judge considered that it was significant that the Appeal Panel did not conclude that the Second Injury was of a kind or nature that severed the causal chain between the First Injury and the Worker's permanent impairment. His Honour said that, if the Appeal Panel had come to such a conclusion, it would have been obliged to find that there was no impairment as a result of the First Injury but that, to the contrary, it had concluded that the Worker's permanent impairment resulted from both the First Injury and the Second Injury.
6. The primary judge considered that the task required by ss 9 and 9A of the Compensation Act was to make a determination about whether the relevant employment was a substantial contributing factor to the relevant injury and then to assess the permanent impairment by clinical assessment of the Worker, as the Worker presented on the day of assessment, having regard to the matters set out in the Guidelines. His Honour held that that task did not involve any process of apportionment between injuries. His Honour observed that, while s 323 of the Management Act provided an exception to that general approach in the limited circumstances that that provision contemplates, the provision did not apply in the present case.
7. For those reasons, the primary judge was satisfied that the medical assessment certificate issued pursuant to the determination by the Appeal Panel on 18 July 2018 contained an error on its face and the Worker was entitled to succeed in her claim. His Honour considered that it followed from that conclusion that the decision that ought to have been reached by the Appeal Panel was that the whole person impairment of the Worker was 19% and not 6%. Accordingly, on 3 May 2019, his Honour made orders quashing the decision of the Appeal Panel of 18 July 2018 and ordering that the matter be remitted to the Registrar to be dealt with in accordance with law. His Honour ordered the Secretary to pay the Worker's costs of the proceedings.

The Appeal

1. By summons dated 30 July 2019, the Secretary seeks leave to appeal from the orders made by the primary judge. The proposed grounds of appeal are that his Honour erred in: 1. holding that principles of causation applied in tort are not applicable in determining whether an impairment is a result of an injury for the purposes of ss 319(c) and 326(1)(a) of the Management Act; 2. alternatively, holding that the applicable common law principles in the circumstances required that the Appeal Panel find that the entirety of the whole person impairment of the Worker was the result of the First Injury, without allowing for apportionment on account of the permanent impairment resulting from the Second Injury; and 3. holding that the Appeal Panel erred in failing to reach a decision that the Worker's whole person impairment that was the result of the First Injury was 19% rather than 6%.
2. The Secretary formulated two questions for this Court and the Worker did not dissent from that formulation. The questions are as follows: 1. Whether, in the case of a subsequent injury, common law principles relating to causation apply to an assessment made under Pt 7 of Ch 7 of the Management Act in relation to the earlier injury. 2. Whether in the circumstances of this case, the common law principles required the Appeal Panel to determine that the entirety of the whole person impairment assessed by it, in reliance on the assessment by the AMS, was the result of the First Injury, without allowing for apportionment on account of impairment resulting from the Second Injury.

Common Law Causation Principles

1. The problems of causation such as are raised by the Secretary's contentions are not new to the law and were raised in relation to liability under the Lex Aquilia, enacted during the mid-years of the Roman Republic. Under Ch 1 of the Lex Aquilia, a person, who, without justification or wrongfully, caused the death of a slave, was liable to the owner of the slave for the highest value that the slave had had in the previous 12 months. [2] Under Ch 3 of the Lex Aquilia, a person, who, without justification or wrongfully, occasioned a non-mortal injury to a slave was liable to the owner of the slave for the value of the injury caused. [3] Justinian's Digest, published in AD 533, recorded the conflicting opinions of Ulpian and Julian as to the liability of successive wrongdoers in circumstances where the first wrongdoer causes a mortal injury to a slave but before the slave dies, a second wrongdoer causes a second mortal injury to the slave that results in immediate death. [4] The issue between Julian and Ulpian concerns the question of whether the first wrongdoer, who occasioned mortal injury that does not result in immediate death, will be liable under Ch 1 or Ch 3 of the Lex Aquilia. In the course of Roman legal scholarship over many centuries, various solutions have been suggested, none entirely satisfactory. [5]
2. The Secretary indicated that ground one was raised on the basis that it was not clear from the reasons of the primary judge as to whether his Honour did in fact conclude that principles of causation in relation to claims in tort are not applicable for the purposes of determining workers compensation entitlements. That is to say, the Secretary contends that the primary judge appears to have focussed on the first causation test, in ss 9 and 9A of the Compensation Act, but not on the second causation test, in ss 319(c) and 326(1)(a) of the Management Act. The application of the first causation test was not in issue.
3. The Secretary contends that, if the primary decision is to be interpreted as having rejected the applicability of the common law principles in the second causation test, because there is no express provision for apportionment in the case of a subsequent injury (in contrast to s 323), then there is legal error. The Secretary indicated that, with respect to ground two, an alternative reading of the primary decision is that the primary judge accepted that common law principles of causation should be applied in determining whether the impairment was "as a result of" the First Injury, but concluded that the Appeal Panel erred in applying the principles, which in the circumstances of the case precluded apportionment.
4. The Worker accepts that a global award of common law damages in a personal injuries case is an amalgam of different heads of damage that may not all necessarily be affected by another injury, whether that injury be earlier or later than the compensable injury. For example, a second injury to which common law liability does not attach may affect capacity to earn on the open market but not non-economic loss, just as a second injury may affect non-economic loss but not affect capacity to earn on the open market. However, the Worker points to the fact that no-fault statutory workers compensation entitlements, such as for total or partial incapacity for work and whole person impairment, are conceptually different from a global award of common law damages in a personal injuries case.
5. The Worker contends that nothing in the Management Act or the Guidelines displaces the relevant law of causation that has been applied since the enactment of the Management Act, such that "statutory causation" is satisfied if the injury in question is a material contributing cause of the compensable consequence contended for by a worker. Thus, in the case of incapacity, need for medical expense or whole person impairment, the Worker contends, the consequence is the whole consequence and not a proportion or fraction of it.
6. In common law contexts, an injury or incapacity may be attributable, in the legal sense, to more than one cause operating concurrently. [6] There is no difference between the legal view of causation in tort and causation in the field of workers compensation, subject to the qualification that, in a claim for workers compensation, it is unnecessary to prove that the incapacity was the natural and probable consequence of the injury. That is to say, the question of foreseeability does not arise. It is sufficient that the incapacity results from the injury by a chain of legal causation unbroken by a novus actus interveniens. [7]
7. Two causation tests are involved in a medical assessment of permanent impairment under Pt 7 of Ch 7 of the Management Act. The first test arises from the provisions of ss 9 and 9A of Compensation Act. That is to say, it must be shown that the injury that gave rise to the impairment in question arose out of or in the course of employment that and that the employment was a substantial contributing factor to the injury. The second test arises from the provisions of ss 319(c) and 326(1)(a) of the Management Act. That is to say, it must be shown that the permanent impairment is as a result of the injury.
8. The phrase "the degree of permanent impairment of the person as a result of an injury" appears in both ss 319(c) and s 326(1)(a) of the Management Act. That composite phrase requires an enquiry as to the causal connection between the degree, or percentage, of assessed permanent impairment of a worker, on the one hand, and the compensable injury, on the other. That is to say, it was necessary for the AMS and the Appeal Panel to assess the degree, or percentage, of whole person impairment of the Worker that was caused by or is attributable to the First Injury. In doing so, common law principles of causation in tort are to be applied.

Worker's Contentions as to application of Principles

1. The Worker claims lump sum compensation in relation to permanent impairment of a psychological or psychiatric character. Such impairment is of different character from what might be described as a physical impairment, such as to a limb of a worker. Where a limb is the subject of permanent impairment as the result of a compensable injury to that limb, it would be relatively straight forward to determine the degree of that impairment even if another injury to the same limb resulted in further impairment. However, the assessment of psychological impairment is not quite as straight forward. That is apparent from the provisions of Ch 11 of the Guidelines.
2. Chapter 11 of the Guidelines deals with "Psychiatric and Psychological Disorders" and sets out the method for assessing psychiatric impairment, the evaluation of which requires a medical examination by a psychiatrist who has undergone appropriate training in the assessment method. Permanent impairment assessments for psychiatric and psychological disorders are only required where the primary injury is a psychological one. The psychiatrist must confirm that the psychiatric diagnosis is the injured worker's primary diagnosis. Under Section 11.4, the impairment rating must be based upon a psychiatric diagnosis according to a recognised diagnostic system and the report must specify the diagnostic criteria upon which the diagnosis is based.
3. Under Section 11.7, a psychiatric disorder is permanent if, in the opinion of the assessor, it is likely to continue indefinitely. Section 11.10 relevantly provides that, to measure the impairment caused by a work-related injury or incident, the psychiatrist must measure the proportion of whole person impairment due to any pre-existing condition. Pre-existing impairment is calculated using the same method as is used for calculating current impairment level. All available information is used to rate the injured worker's pre-injury level of functioning in each of the relevant areas of function and the percentage impairment is then calculated as specified in the Guidelines. The injured worker's current level of whole person impairment is assessed and the pre-existing whole person impairment percentage is subtracted from the current level to obtain the percentage of permanent impairment directly attributable to the work-related injury. If the percentage of pre-existing impairment cannot be assessed, the deduction is 1/10th of the assessed whole person impairment. That reflects s 323.
4. Under Section 11.11, behavioural consequences of psychiatric disorder are assessed on six scales, each of which evaluates an area of functional impairment. The six scales are as follows:
5. Self-care and personal hygiene.
6. Social and recreational activities.
7. Travel.
8. Social functioning (relationships).
9. Concentration, persistence and pace.
10. Employability. Impairment in each area is rated using class descriptors. Classes range from one to five, in accordance with severity.
11. The Worker asserts that the Appeal Panel did not properly consider or direct itself correctly in principle, in so far as it assumed that a question of "apportionment" arose in relation to the Second Injury. She contends that the Appeal Panel's view of the effect of the First Injury and a proper application of the law of causation required the conclusion that the First Injury was a material contributing cause of her whole person impairment, in that it was a causal factor without which her whole person impairment would not have existed as it did.
12. The Worker asserts that the fact that the Parliament expressly allowed a deduction from an assessed totality of whole person impairment by reference only to pre-injury factors indicates that the situation was to be different in respect of subsequent factors. She says that the Parliament had the opportunity to deal both with the past and with subsequent events in considering reduction of whole person impairment but chose to deal only with past events. She contends, therefore, that the inference should be drawn that deductions by reference to subsequent events are not required, provided that an established level of causation is made out and that reduction in respect of subsequent events should be confined to "clear cases" where, for example:

• the effects of the particular injury under consideration have ceased;
• the causal chain is clearly "snapped"; or
• an intervening subsequent causal factor has clearly ousted or supplanted any continuing contribution to impairment by the compensable injury. That contention raises the question as to whether, as a matter of construction of ss 319 and 326, the express provision in s 323, for apportionment where there is an injury prior to the compensable injury, precludes making an apportionment with regard to an injury that occurs after the compensable injury.

1. One possible explanation for the provision in s 323 in relation to an injury prior to the compensable injury and the absence of a similar provision in relation to an injury subsequent to the compensable injury is that, in the ordinary course, there may be no occasion to assess the degree of impairment resulting from an earlier injury, whether it be work-related or otherwise. On the other hand, in ordinary circumstances, a claim for compensation would be made relatively soon after the occurrence of a compensable injury and any medical dispute would arise and be determined relatively soon after the compensable injury, prior to the intervention of any subsequent injury. Clearly, if an authorised medical specialist or an Appeal Panel were required to assess whole of person impairment, before a subsequent injury, the subsequent injury would be completely irrelevant. The fact that a subsequent injury fortuitously intervened between the compensable injury and the assessment would not obviate the need for a medical assessment certificate to assess the degree of whole person impairment that resulted from the injury.
2. The Worker acknowledges that the outcome contended for by her creates "a jarring note" when considered in the context of her concurrent claim in respect of the same overall physical condition based on the Second Injury. Her response is that each of the Secretary and Hostels, the respective employers in relation to the two injuries, knows of the injury suffered in the employ of the other and will be able to take steps to prevent double recovery. She asserts that each employer held to be liable can take into account any relevant liability established against the other and that, if there is overlap, double compensation can be avoided.
3. In that regard, it is of significance that the Secretary learned of the Worker's claim in relation to the Second Injury only when information as to the Second Injury was contained in the response to the Secretary's request, in the context of an application for further assessment, for particulars of the Worker's employment activities since 1 September 2016. Thus, the AMS had issued the First AMS Certificate without being aware of the Second Injury. Further, there is no evidence as to whether the Worker has informed Comcare of the claim made by the Worker on the Secretary in respect of the First Injury. More significantly, the Worker points to no statutory mechanism whereby double compensation would be avoided in circumstances such as those that have arisen in the present case.
4. Section 22 of the Compensation Act deals with the question of permanent impairment suffered by a Worker that results from more than one injury to the Worker. Under s 22(1)(b), liability to pay compensation is to be apportioned in such manner as the Commission determines. However, s 22 has no operation in the present circumstances since Hostels is not amenable to the Compensation Act or the Management Act. Rather, the entitlement of the Worker to compensation in respect of the Second Injury is regulated by Commonwealth legislation.

Error on the part of the Appeal Panel

1. The Appeal Panel evaluated the medical and other evidence before it and found that the Worker had given an unreliable and inaccurate history to various medical practitioners, that she had intended to mislead the AMS when he provided the Second AMS Certificate and that she had succeeded in doing so. The Appeal Panel considered that more accurate histories had been taken by the medical practitioners whose reports were submitted by the Worker to Comcare in support of her application for compensation with respect to the Second Injury, suffered while employed by Hostels. In those histories, the Worker stated that she had completely recovered from the First Injury when she commenced employment with Hostels. Accordingly, the Appeal Panel held, the Second AMS Certificate contained error in relation to the assessment of the impact of the Second Injury on the Worker's permanent impairment. It therefore proceeded to make its own assessment.
2. The Appeal Panel found that the First Injury had resulted in only minor impairment by the time of the Worker's commencement of employment with Hostels and during the time of her employment prior to the occurrence of the Second Injury. The Appeal Panel found, therefore, that the Second Injury, while employed by Hostels, substantially contributed to the degree of whole person impairment of the Worker. The Appeal Panel then sought to determine the degree of whole person impairment that resulted from the First Injury, as distinct from the degree of whole person impairment that resulted from the Second Injury.
3. The Appeal Panel found that, after leaving employment by the Secretary, the Worker was able to secure employment with Hostels, faced a more confronting situation in that employment, was terminated because she stood up for herself and was mentally strong enough to bring proceedings in the Fair Work Commission to obtain reinstatement after being wrongfully dismissed. The Appeal Panel then found that, while employed by Hostels, the Worker faced highly traumatic events far greater than those suffered while employed by the Secretary and ceased employment in March 2017, when she was assessed as having suffered the Second Injury.
4. The Appeal Panel found that, when the Worker commenced her employment with Hostels, she was not suffering from any chronic psychological disorder and that she continued in that state until the time when she sustained the Second Injury. Nevertheless, the Appeal Panel found that the First Injury had some continuing effect and contributed to the Worker's permanent impairment but at a lower level than the level at which the Second Injury contributed to her impairment.
5. The question for determination by the Appeal Panel was the degree of permanent impairment now suffered by the Worker as a result of the First Injury. That question was one of fact and the Appeal Panel's reasoning was consistent with conventional principles of causation. There are three possible categories where an earlier injury is followed by a later injury, as follows: [8]

• Where the later injury results from a subsequent accident that would not have occurred had the victim not been in the physical condition caused by the earlier accident, the second injury should be treated as having a causal connection with the earlier accident.
• Where an earlier injury is exacerbated by a subsequent injury, there will be a causal connection between the original injury and the subsequent damage unless it can be shown that some part of the subsequent damage would have been occasioned even if the original injury had not occurred.
• Where a victim, who had previously suffered an injury, suffers a subsequent injury and the subsequent injury would have occurred whether or not the victim had suffered the original injury and the damage sustained by reason of the subsequent injury includes no element of aggravation of the earlier injury, there will be no causal connection between the original injury and the damage subsequently sustained.

1. There has been no finding that the Second Injury resulted in greater permanent impairment than would have been sustained by the Worker if she had not sustained the First Injury. There has been no finding that the current level of permanent impairment suffered by the Worker is the result of aggravation of the First Injury by the Second Injury. There has been no finding that the incident while employed by Hostels occurred only because of the First Injury. Rather, the findings demonstrate that the Second Injury resulted from the subsequent incident that occurred while the Worker was employed by Hostels and the Second Injury would have occurred even if the First Injury had not occurred, such that the Second Injury and First Injury are causally independent of each other. In those circumstances, it was necessary for the Appeal Panel to assess the extent of continuing permanent impairment of the Worker that is attributable to the First Injury.
2. The Appeal Panel undertook an exercise, which it described as one of apportionment, to assess the "degree" of the Worker's permanent impairment that resulted from the First Injury. There may be a question as to whether, contrary to the approach adopted by the Appeal Panel, the second category described above was relevant to that assessment. Whilst the Secretary's argument proceeded on the assumption that only the third category was relevant, there was some material before the Appeal Panel that suggests that, following the First Injury, the Worker was in a more vulnerable position and exposed to a greater level of injury than might have otherwise been the case.
3. There is a cause for some disquiet as to the process undertaken by the Appeal Panel in making its assessment. The Appeal Panel relied on the examination of the Worker by the AMS, as described in the reasons for his two decisions, and did not undertake a fresh examination of her. Nevertheless, the Appeal Panel reached a different conclusion from that reached by the AMS and, in doing so, made significant adverse credibility findings in relation to the Worker. That is to say, whereas the AMS attributed inconsistencies in the histories given by the Worker to her psychiatric or psychological condition, the Appeal Panel, without directly hearing from the Worker, took quite a different view, namely, that the Worker engaged in conduct that was misleading and deceptive.
4. Related to that concern is the finding on which the Appeal Panel's assessment of 6% whole person impairment was based. The Appeal Panel concluded that the assault that gave rise to the First Injury contributed "only a minority of the level" of her permanent impairment when compared to the Second Injury, which the Appeal Panel characterised as "significant traumatic psychological injury". The Appeal Panel did not undertake, in its reasons, any detailed comparison of the respective seriousness of the two incidents. Rather, the Appeal Panel appears to have placed considerable weight on the Worker's own characterisation of the First Injury, as contained in the claim form addressed to Comcare.
5. The complaint made by the Worker to the police in relation to the assault that gave rise to the First Injury was that, when the Worker asked a male student to cease using a mobile telephone during class, the student became agitated and began yelling abuse and vulgar language at her. She said that she was attacked physically and verbally by the student while two other male students observed the assault without intervening. The Worker said that she was frightened for her life and was unsure what was going to happen to her. She said that the student ran up to her, swung her around the room, hitting her, punching her, grabbing her breasts, hitting her face, eye, neck, wrist and arm and continuing to threaten her life while he continued punching her and swinging her around while digging in his nails, drawing blood on her arms and leaving her with bruises and red marks. It was not suggested to the Worker by the Appeal Panel that her statement to the police to that effect was in any way inaccurate. If that description of the assault is unchallenged, the characterisation of the incident by the Appeal Panel as "a minor assault" is difficult to accept.

Conclusion

1. The orders of the primary judge simply quash the decision of the Appeal Panel and order that the matter be remitted to be dealt with in accordance with law. The appropriate orders are that leave to appeal be granted and that the appeal be dismissed with costs.
2. SIMPSON AJA: I have read in draft the judgment of Emmett AJA. For the following reasons, I agree with the orders proposed. In order to make my reasons clear, it is necessary to restate the relevant facts and circumstances.
3. The first respondent (Ms Elaine Johnson, to whom, as she is the only respondent participating in the appeal, I will refer as "the respondent") was employed by the Secretary, NSW Department of Education ("the appellant") as a teacher in the Home Economics faculty at Fairvale High School from 28 April 2014. On the third day of her employment (30 April 2014) she was subject to an assault by a student, with whom she had had a dispute on a disciplinary matter concerning his use of a mobile telephone. Subsequently, in a statutory declaration, the respondent described the assault in the following terms: "I was attacked physically and verbally by the male student come to be known to me as [RP] whilst two other unknown males students of the same school returned into their classroom during some part of the attack and observed the physical and verbal assault taking place on me during the attack I did not know if they were going to join him in the attack I did not see their faces I only saw legs, shoes, jumpers. I was frightened for my life I was unsure what was going to happen to me I know I needed to get out of the room but he would not let me go. I just know that I needed to get out of the room. I was unsure if I was going to be raped, murdered, stabbed, beaten as it is so isolated from the rest of the school and there was no people around except the two males in the room besides [RP] and I was unsure if they were going to set upon me as well and the bell had gone. I had my teachers diary, and [RP's] mobile phone in my hand, he ran up at me and swung me around the room, yelling abuse, hitting me, punching, grabbing my breasts, hitting my face, eye, neck, right wrist and arm and continued to threaten my life he continued to attempt punching me and swinging me around while digging in his nails drawing blood on my arm and leaving me with bruises and red marks to many parts of my body I am unsure of how long this went on for as I was focused on trying to escape from him. At some stage he let me go took his phone and he left the room he turned around and came back into the room then proceeded to spit on me and then he laughed. He then walked outside I stood in the doorway to make sure I could leave safely and there was a group of male students that he joined on the pathway outside and walked off …" (reproduced as in original)
4. Later, in a statement to police, the respondent said that the incident occurred in a demountable building at the rear of the school grounds near the oval. The building was quite secluded from other buildings.
5. So far as the evidence discloses, no issue has ever been taken with the accuracy of this description.
6. The respondent, it seems clear, has not returned to her employment with the appellant since that date. In July 2016 she commenced employment with a Commonwealth organisation, Aboriginal Hostels Ltd ("Aboriginal Hostels"). There, it seems, she was also subjected to abusive behaviour by students. In a letter dated 24 March 2017 she described various incidents of such behaviour, summarised as follows: "I have been left to feel demoralised, bullied, threatened, intimidated, screamed at, pushed and sworn at including sexual innuendo." She went on to give a detailed description of some of the events to which she referred. She gave various dates in February 2017 and 24 March 2017 as the dates of the incidents she described. Although in the letter the respondent gave accounts of a number of unpleasant incidents involving students at a hostel conducted by Aboriginal Hostels, none is remotely comparable with that of 30 April 2014 at Fairvale High School.
7. On 3 August 2016 the respondent made an application for compensation under the Workers Compensation Act 1987 (NSW). It is the outcome of this application which is the subject of the present appeal.

Applicable legislation

1. Before proceeding with the narrative of relevant events, it is convenient to outline the applicable legislative provisions. Those are to be found in the Workers Compensation Act ("WC Act") and the Workplace Injury Management and Workers Compensation Act 1998 (NSW) ("the WIM Act"). Section 4 of the WC Act defines "injury", relevantly, as: (a) … personal injury arising out of or in the course of employment
2. By s 9(1) a worker who has received an injury is to receive compensation from his or her employer in accordance with the WC Act. By s 9A(1) no compensation is payable under the Act in respect of an injury unless the employment concerned was "a substantial contributing factor" to the injury.
3. The WC Act provides for various forms of compensation to which an injured worker is entitled. Relevantly, s 66(1) provides: (1) A worker who receives an injury that results in a degree of permanent impairment greater than 10% is entitled to receive from the worker's employer compensation for that permanent impairment as provided by this section. Permanent impairment compensation is in addition to any other compensation under this Act.
4. The remainder of s 66 sets out a sliding scale of what is commonly known as "lump sum compensation" payable depending on the degree of permanent impairment. By s 65(1) the degree of permanent impairment is to be assessed in accordance with Ch 7, Pt 7 (ss 319-331) of the WIM Act.
5. By s 105(1) of the WIM Act (but subject to some presently immaterial exceptions) the Workers Compensation Commission ("the Commission") has exclusive jurisdiction to examine, hear and determine all matters arising under either the WC Act or the WIM Act.
6. By s 293 of the WIM Act, where a dispute referred to the Commission for determination concerns a "medical dispute" (as defined in s 319) the Registrar of the Commission may, subject to any relevant regulations with respect to the assessment of permanent impairment, refer the dispute for medical assessment under Pt 7 of Ch 7. "Medical dispute" is defined as a dispute about, relevantly: (c) the degree of permanent impairment of the worker as a result of an injury
7. For the purpose of the assessment of medical disputes, pursuant to s 320 of the WIM Act, the President of the Commission has appointed medical practitioners as "approved medical specialists" ("AMS"). By s 325 an AMS to whom a medical dispute is referred is required to give a certificate ("a medical assessment certificate") as to the matters referred for assessment.
8. By s 327 parties to a medical dispute may apply to the Registrar for an appeal against the medical assessment certificate. The grounds on which such an appeal may be made are limited, and include: (3) … (c) the assessment was made on the basis of incorrect criteria, (d) the medical assessment certificate contains a demonstrable error.
9. By s 329, a matter referred for assessment may be referred again, but only by the Registrar as an alternative to an appeal against the assessment as provided by s 327, or by a court or the Commission.
10. Section 323 provides for deduction in the assessment of the degree of permanent impairment resulting from an injury to take account of "any proportion of the impairment that is due to any previous injury", whether or not that impairment is compensable. By subs (2), if the calculation of such a deduction will be difficult or costly to determine, it is to be assumed, for the purpose of avoiding disputation, that the deduction is 10% of the impairment "unless this assumption is at odds with the available evidence".
11. By s 376 the State Insurance Regulatory Authority (constituted under the State Insurance and Care Governance Act 2015 (NSW)) ("the Authority") may issue Guidelines with respect to, inter alia, the assessment of the degree of permanent impairment of an injured worker as a result of an injury. The Authority has in fact issued Guidelines with respect to the assessment of permanent impairment by reason of psychiatric injury.

The narrative of relevant facts

1. I return now to the factual narrative. The respondent claimed that, by reason of the assault at Fairvale High School, she suffered psychiatric injury within the meaning of s 4(a) of the WC Act. By s 9 of the WC Act, if that claim were made good, she would be entitled to compensation in accordance with other provisions of the WC Act. If, in addition, she were able to establish that the injury resulted in permanent impairment greater than 10%, she would also be entitled to receive lump sum compensation in accordance with the detailed provisions of s 66 of the WC Act.
2. On 10 March 2017 the respondent filed in the Commission an application to resolve a dispute. She identified the dispute as "lump sum compensation where degree of permanent impairment in dispute". She identified the injury as "Post-traumatic Stress Disorder" and "Reactive Depression". She said that the injury occurred as a result of: "Abused, threatened and ultimately physically assaulted by a student." She supported her claim with a number of medical reports. One such report, dated 10 July 2016, by Dr Ben Teoh (a consultant psychiatrist) assessed the respondent's "whole person impairment" as at that date as 17%.
3. In accordance with s 293 of the WC Act the Registrar of the Commission referred the respondent's claim to an AMS, Associate Professor Robertson (a psychiatrist). On 2 June 2017 the AMS examined the respondent. On 9 June 2017, on the basis of his examination, and the material presented to him (which did not include any reference to the respondent's experiences while she was employed by Aboriginal Hostels) the AMS assessed her as suffering 19% permanent impairment as a result of the injury. The AMS found: "[The respondent] now presents with evidence of a persistent depressive disorder which appears to be a direct consequence of the indexed trauma. She has some 'cross cutting' features of [post-traumatic stress disorder]. But this full syndrome is no longer present." He issued a medical assessment certificate to that effect. Implicit in the medical assessment certificate is acceptance that the respondent suffered injury arising out of or in the course of her employment with the appellant.
4. There is nothing in the AMS's certificate to indicate that he was aware of the events at Aboriginal Hostels, or that the respondent had made a claim for compensation under Commonwealth legislation arising out of the events during her employment with Aboriginal Hostels.
5. On 24 April 2017 the respondent made a claim under the relevant Commonwealth legislation in relation to her experiences while employed by Aboriginal Hostels. In answer to a question concerning the condition in respect of which she was claiming, she replied: "- Bullying - harassment - intimidation - threats of violence - sexual harassment - threats of physical violence" (It may here be observed that that litany of allegations does not meet the description of "the condition" in respect of which she claimed compensation. I will assume, in the appellant's favour, that the claim should be interpreted as a claim for psychological or psychiatric injury not markedly different from that the respondent asserted she suffered as a consequence of the assault at Fairvale High School.)
6. In response to a question asking whether she had ever experienced "a similar symptom, injury or illness, work related or otherwise", the respondent ticked the box for "No". In response to the following question: "Have you ever claimed compensation through any insurer, for a similar injury or condition (eg, claims with the Department of Veterans Affairs, the Dust Diseases Tribunal, or involving a motor vehicle accident)?" she again ticked the box for "No".
7. A psychiatrist, Dr Ash Takyar, examined the respondent on 3 November 2017. Dr Takyar recorded a variety of complaints made by the respondent concerning her employment by Aboriginal Hostels (many of which did not concern any bullying or intimidation by students). He also recorded that the respondent told him that she had been diagnosed in 2014 with post-traumatic stress disorder, "in the context of an event", the details of which she did not disclose. Dr Takyar recorded that the respondent said that she had made a full recovery.
8. Dr Takyar diagnosed: "… a history of an adjustment disorder with mixed anxiety and depressed mood in the context of the events described in the report above." (that is, the events concerning the respondent's employment with Aboriginal Hostels.)
9. On 18 January 2017 the appellant applied to the Commission to exercise its power under s 329(1)(b) of the WIM Act for a further referral for medical assessment, and to admit "late documents" in support of the application. The "late documents" related to the respondent's claim for compensation under Commonwealth legislation. The application was granted and the respondent's claim was referred again to Associate Professor Robertson as AMS for further assessment in the light of those documents.
10. On 3 April 2018 the AMS again examined the respondent. He issued a second medical assessment certificate on 11 April 2018. In doing so, he took into account the additional material concerning the respondent's employment at Aboriginal Hostels and concluded: "Having had the opportunity to review additional information and re-examine [the respondent], I remain of the view that she presents with a persisting or chronic post-traumatic stress disorder that, in all probability, was exacerbated in the subsequent employment with Aboriginal Hostels Ltd. Having been provided with additional information, it is evident that the history as reported across multiple examiners at different points is inconsistent and unreliable. Whilst I did not observe any evidence that [the respondent] was dissimulated or over reporting her symptoms and her clinical presentation was overall genuine, the narrated history is often lacking in detail, particularly for previous events … Applying the principle of charity, [the respondent's] apparent problems narrating her history is a function of her psychiatric symptoms rather than any intent to mislead. What is clearly evident is that [the respondent] developed a psychological injury in the course of her duties with [the appellant] that manifest as chronic post-traumatic stress disorder that was evident at my previous examination. What is now clear is that the injury was exacerbated by subsequent employment with Aboriginal Hostels Ltd and that some of the observed level of [whole person impairment] (unchanged since my last assessment) must be attributed to the presumed exacerbating effects of this. Given the problems with history and [the respondent's] incapacity to narrate a clear account of the effects of this, the only acceptable methodology would be a deduction of 1/10th of the observed WPI."
11. The AMS again assessed the permanent impairment suffered by the respondent as 19%, but, purportedly in accordance with s 323 of the WC Act, deducted 10%, yielding a result of permanent impairment as a result of the injury of 17%. This would have entitled the respondent to lump sum compensation under s 66 of the WC Act.
12. Pursuant to s 327 of the WIM Act, the appellant sought, and was granted, an appeal against the certificate. It identified the grounds as: "The assessment was made on the basis of incorrect criteria and that the medical assessment certificate contained a demonstrable error." These are the grounds permitted under s 327(3)(c) and (d).
13. The appeal came before a Medical Appeal Panel constituted under s 328(1) of the WIM Act. It was common ground that the AMS's approach was erroneous because s 323 of the WC Act provides for deduction or apportionment related to a previous, but not a subsequent, injury.
14. The members of the Appeal Panel did not examine the respondent. Rather, they reviewed the extensive medical reports that had been accumulated. Although the Appeal Panel accepted that the respondent suffered 19% whole person impairment, it did not accept that the entirety of that impairment was attributable to the injury suffered at Fairvale High School. It considered that that injury contributed only a minority of the level of whole person impairment which it quantified as "at most one third" of that impairment. On 18 January 2018 the Appeal Panel upheld the appeal and issued a medical assessment certificate assessing the respondent's degree of permanent impairment resulting from the injury as 6%. This is an assessment that does not entitle the respondent to lump sum compensation under s 66.
15. The Appeal Panel gave lengthy reasons for its decision. It was satisfied (as was common ground) that the AMS fell into error in deducting 10% purportedly pursuant to s 323 of the WIM Act. It went on to consider what it called "the next matter to consider", that being: "the question of apportionment between the subject work injury and the psychological injury sustained by the respondent whilst in the employ of the Aboriginal Hostels Ltd."
16. The Appeal Panel said: "111 There is no dispute that the respondent suffered a psychological injury in the employ of the appellant. She was diagnosed as suffering from a Post-traumatic Stress Disorder and/or an Adjustment Disorder with Mixed Depressed and Anxious Mood as a result of the work assault. Dr Teoh assessed 17% whole person impairment, but his examination was undertaken some two weeks prior to the respondent gaining employment with Aboriginal Hostels Ltd."
17. The Appeal Panel then reviewed a number of medical reports, and said: "126 The appellant does not take issue with the whole person impairment assessed by the AMS. In the Panel's opinion, it was open to the AMS to assess the degree of the respondent's whole person impairment in the manner that he did and this discloses no error on his part. The Panel is satisfied that the respondent has been properly assessed as having 19% whole person impairment as a result of the cumulative effect of his [sic] two work injuries. 127 In the Panel's view, the AMS has fallen into error in relation to assessment of the impact that the respondent's subsequent injury had on her mental state. The AMS advised that the respondent's difficulty in relation [to] a correct history was due to her psychiatric symptoms rather than any intent to mislead. The Panel does not hold that view and agrees that the respondent's evidence is unreliable. 128 The AMS did not explain precisely what caused the respondent to give inaccurate evidence to the various doctors. This was not an isolated instance. Accordingly, the Panel is not satisfied that the AMS properly applied his clinical judgement and provided adequate reasons for his assessment. 129 The AMS assessed the respondent's employability under Table 11.6 [of the Permanent Impairment Guidelines] as coming within Class 4. Whilst that would be acceptable when one has regard to the impact of the injury sustained at Aboriginal Hostels Ltd, it is inconsistent with the history of the respondent's employment after she left the appellant. The doctor's conclusion was clearly compromised by the respondent's unreliable and inaccurate history, which itself is of little probative value. 130. The evidence confirms that the respondent suffered a psychological injury at the appellant as a result of a minor assault. It was thought that this injury was incapacitating, and yet she was able to secure employment with the Aboriginal Hostels Ltd. 131. The respondent worked for the Aboriginal Hostels Ltd for 10 months, not a matter of days or weeks. It was not a failed work trial. She was employed in a far more confronting position. She had interpersonal issues with the CEO and her services were terminated because she stood up for herself, not because she was suffering from any chronic psychological disorder. 132. The respondent was mentally strong enough to initiate legal proceedings in the Fair Work Commission. She succeeded in her claim and was reinstated. She eventually ceased work in March 2017 and was certified as unfit by Dr Rahman as a consequence of being exposed to highly traumatic events that comprised of aggressive behaviour and threats to her life. The number and nature of events, and degree of threat to the respondent at Aboriginal Hostels Ltd are recorded as far greater than those at the original employer. 133. The Panel considers that the injury sustained by the respondent in 2014, when she was employed by the appellant, contributes only a minority of the level of the respondent's whole person impairment when compared to the significant traumatic psychological injury sustained by the respondent in the employ of Aboriginal Hostels Ltd in early 2017. 134. Accordingly, the Panel is satisfied that the respondent's injury at the appellant contributes at most one-third to the degree of the respondent's whole person impairment, or 6% whole person impairment." (emphasis added)
18. The Appeal Panel therefore issued the medical assessment certificate mentioned above.

The proceedings in the Supreme Court

1. Pursuant to s 69 of the Supreme Court Act 1970 (NSW) the respondent applied to the Supreme Court for an order setting aside the decision of the Appeal Panel and remitting the matter to a differently constituted appeal panel to be determined according to law.
2. The relief which may be obtained under s 69 of the Supreme Court Act is limited. It is available only for jurisdictional error or error of law on the face of the record. The respondent asserted error of both kinds in the determination of the Appeal Panel.
3. The application was heard in the Common Law Division of the Supreme Court. On behalf of the respondent two independent contentions asserting relevant error were advanced. The first was that the Appeal Panel failed to discharge its duty to make and state a diagnosis. The primary judge rejected this contention. It need not be further considered.
4. The second contention made on behalf of the respondent concerned the approach taken by the Appeal Panel to the issue of the cause of the respondent's injury. This was stated by the primary judge to be an issue concerning apportionment of the respondent's degree of permanent impairment between the first and the second injury. The primary judge upheld a contention on behalf of the respondent that the approach taken was erroneous. He said: "67 The task required by ss 9 and 9A of [the WC Act] is for a determination to be made about whether the relevant employment was a substantial contributing factor to the injury. If it was, then the AMS or the Panel is to assess the permanent impairment, by a clinical assessment of the claimant, as they present on the day of the assessment having regard to the matters set out in Clause 1.6 of the Guidelines. That task does not involve any process of apportionment between injuries."
5. His Honour then noted the exception provided by s 323 of the WIM Act which, he correctly observed, applies only to apportionment between an earlier (not a subsequent) injury and the injury under consideration.
6. The primary judge therefore concluded: "70 It follows from this conclusion that, in accordance with the law and in the circumstances which applied at the time the Panel made its assessment, the correct decision which ought to have reached was that the whole person impairment of [the respondent] was 19% and not 6%."
7. His Honour accordingly made the following orders: "(1) Pursuant to s 69 of the Supreme Court Act 1970, the decision of the second defendant made on 18 July 2018 is quashed. (2) Order that the matter be remitted to the first defendant to be dealt with in accordance with law. (3) Third defendant to pay the plaintiff's costs of these proceedings."

The application for leave to appeal

1. The appellant sought leave to appeal against the decision of the primary judge. Leave is required because it is not apparent that the proposed appeal involve a matter at issue amounting to or of the value of $100,000 or more: Supreme Court Act, s 101(2)(r).
2. The applicant identified three proposed grounds of appeal, formulated as follows: "(i) Holding that principles of causation applied in tort are not applicable in determining whether an impairment is a result of an injury for the purposes of ss 319(c) and 326(1)(a) of [the WIM Act]; and (ii) In the alternative, holding that the applicable common law principles in the circumstances required that the Appeal Panel of the [Commission] find that the entirety of the whole person impairment ('WPI') of [the respondent] was the result of the injury that was the subject of the claim, without allowing for apportionment on account of the impairment resulting from a subsequent injury; and (iii) Holding that the Appeal Panel erred in failing to reach a decision that [the respondent's] WPI that was the result of the injury that was the subject of the claim was 19% rather than 6%."
3. The first ground may be disposed of quickly. I do not understand the primary judge to have held that common law principles of causation are not applicable when assessing, under s 293 of the WC Act, the degree of permanent impairment that results from an injury. On the contrary, his Honour said: "66 It is significant that the Panel did not conclude that the later injury was of a kind or nature that severed the causal chain between the NSW Education injury and the plaintiff's impairment. If it had come to such a conclusion, then it was obliged to find that there was no impairment as a result of the NSW Education injury. However, to the contrary, it concluded that the plaintiff's impairment resulted from the NSW Education injury and the later Hostels injury."
4. That is (although, perhaps, somewhat obliquely) consistent with the authorities on which the appellant relied: see Migge v Wormald Bros Industries Ltd [1972] 2 NSWLR 29; Migge v Wormald Bros Industries Ltd (1973) 47 ALJR 236; Kooragang Cement Pty Ltd v Bates (1994) 35 NSWLR 452; Sutherland Shire Council v Baltica General Insurance Co Ltd (1996) 39 NSWLR 87.
5. In support of the second proposed ground the appellant invoked, and placed heavy reliance on, the decision of Malcolm CJ in State Government Insurance Commission v Oakley (1990) 10 MVR 570; [1990] Aust Torts Reports 81-003. In that case, the Chief Justice identified three categories where the issue of causation involves consideration of the effect or impact of a subsequent injury on the determination of the cause of an earlier injury (or, perhaps more accurately, the assessment of damages consequential upon an earlier injury). The observations were made in the context of proceedings at common law in which negligence is alleged, but are equally applicable to the assessment of the degree of permanent impairment resulting from injury under no-fault legislation such as the WC Act. His Honour identified the three categories as: "(1) where the further injury results from a subsequent accident, which would not have occurred had the plaintiff not been in the physical condition caused by the defendant's negligence, the added damage should be treated as caused by that negligence; (2) where the further injury results from a subsequent accident, which would have occurred had the plaintiff been in normal health, but the damage sustained is greater because of aggravation of the earlier injury, the additional damage resulting from the aggravated injury should be treated as caused by the defendant's negligence; and (3) where the further injury results from a subsequent accident which would have occurred had the plaintiff been in normal health and the damage sustained include [sic] no element of aggravation of the earlier injury, the subsequent and further injury should be regarded as causally independent of the first."
6. The appellant's submissions proceeded on the basis that the determination of the Appeal Panel showed that it found that the respondent's case falls within the third Oakley category, and that that finding was correct.
7. The appellant did not address any separate argument to the third proposed ground of appeal.

Determination

1. It was not in issue that the task committed to the Appeal Panel involved an assessment of the degree to which the respondent's unquestioned permanent impairment was attributable to ("resulted from") the injury she suffered at Fairvale High School. That assessment was complicated by her experiences while employed by Aboriginal Hostels.
2. In my opinion there is considerable substance in the appellant's reliance on the three categories stated by Malcolm CJ in Oakley. Those categories have been adopted by this Court in Jefferies v Roads and Traffic Authority of NSW [1997] NSWCA 167 (NSW Court of Appeal, 28 November 1997, unrep); Caltex Tanker Co (Aust) Pty Ltd v Robert Kerr [1999] NSWCA 115; Government Insurance Office of NSW v Aboushadi [1999] NSWCA 396; [1999] Aust Torts Reports 81-531. In the last of these cases Mason P, with whom Meagher JA and Barr J agreed, said: "23 … the question at issue is the extent of liability of the first tortfeasor in a situation where the continuing adverse impact of the first tort is discernible. It is not the law that the commission of a second tort, affecting an already vulnerable plaintiff, by itself puts an end to the liability of the defendant responsible for the first tort …"
3. His Honour went on to refer to the judgment of Windeyer J in Faulkner v Keffalinos (1970) 45 ALJR 80 at 85. Windeyer J said: "There is I think a critical distinction between a supervening happening that prevents a particular damage occurring as a result of the tort and a supervening happening that causes the harm caused by the tort to have added gravity. In the first class of case the supervening event diminishes the damages which flow from the tort: in the second class it merely adds to them, so that the tortfeasor responsible for the first accident remains liable for the harm he caused, which is not merged in the combined result of his wrongdoing and the later event. The distinction is not always either easily made or preserved."
4. The consequence of those authorities is that, in the circumstances of this case, a necessary part of the Appeal Panel's task was to consider, in the light of the medical evidence, into which of the three Oakley categories the respondent's case fell. That analysis was not undertaken by the Appeal Panel.
5. The appellant's argument proceeded on the assumption (unwarranted in my opinion, and without adequate analysis) that only the third Oakley category was relevant.
6. It may be accepted that the first Oakley category can be excluded. There is no reason in the evidence to think that the injury the respondent alleged she suffered in her employment at Aboriginal Hostels would not have occurred but for the injury suffered at Fairvale High School. At least, it may be assumed that the events that she claimed gave rise to that injury would have occurred, regardless of the history of her previous injury. But there is much in the evidence that would support the application of the second Oakley category. While the events at Aboriginal Hostels would, in all probability, have occurred had the respondent been in normal health, there was medical evidence that the respondent was, by reason of events at Fairvale High School, in a vulnerable position, leaving her exposed to a greater level of damage resulting from subsequent events. That issue was not addressed by the Appeal Panel.
7. What was required on the part of the Appeal Panel was a careful analysis of all of the evidence. I do not pretend that task was other than one of some complexity. The Appeal Panel's reasons do not indicate that that task was undertaken. It was insufficient for the Appeal Panel to record and summarise, as it did, the various medical reports. The further step necessary was to grapple with the complexity of a history of a serious assault at Fairvale High School that was found (by Dr Teoh before or coincidental with the commencement of her employment with Aboriginal Hostels) to have resulted in 17% whole person impairment, followed by a series of less serious incidents during her employment with Aboriginal Hostels.
8. The Appeal Panel simply failed to address that case. I agree with Emmett AJA (at [71]) that there have been no findings either as to whether the respondent's current level of impairment is due to aggravation of the injury suffered by her at Fairvale High School, or whether any injury suffered by her at Aboriginal Hostels occurred only because the respondent was, by reason of the original injury, vulnerable to the events that occurred at Aboriginal Hostels. Attention to such considerations was, in my opinion, essential to the discharge of the functions of the Appeal Panel.
9. Failure to address a case advanced on behalf of a party is constructive failure to exercise jurisdiction and constitutes jurisdictional error: Dranichnikov v Minister for Immigration and Multicultural Affairs [2003] HCA 26; (2003) 77 ALJR 1088.
10. Moreover, a fundamental error in the Appeal Panel's approach is to be found in [130] and [131] of its reasons (extracted above). In [130] the Appeal Panel described the assault suffered by the respondent at Fairvale High School as a "minor assault"; this is a clear indication that the Appeal Panel did not address itself to the case made on behalf of the respondent. That case was that the assault at Fairvale High School was of such significance as to result in permanent impairment. That case was supported by medical reports that pre-dated the respondent's employment at Aboriginal Hostels. Notwithstanding that, in its reasons, the Appeal Panel summarised in some detail the various reports on which each of the parties relied, in that section of its certificate that dealt with its "Findings and Reasons" it did not come to grips with or engage with the implications of those assessments. Nor did it ever come to grips or engage with the seriousness of the assault as described by the respondent, and which appears never to have been contested. The characterisation by the Appeal Panel of that assault as "minor" was a foundation stone in its reasoning process and affords evidence that the Appeal Panel failed to address the case made on behalf of the respondent. This was no mere factual error. It undermined the foundation of the Appeal Panel's approach.
11. In those circumstances I would accept, as did the primary judge, that the certificate of the Appeal Panel was affected by jurisdictional error. I do not accept his Honour's finding at [70] that the "correct decision which it ought to have reached" was that the whole person impairment of the respondent was 19% and not 6%. That determination is one to be made within the procedures provided in Ch 7 Pt 7 of the WIM Act. It is not a determination to be made on judicial review.
12. In my opinion the orders sought in the Supreme Court by the respondent were properly made, and the proceedings properly remitted to the Commission to be determined according to law. That does not imply that the only result of that re-determination should be that the permanent impairment of the respondent as a result of the injury was 19%. That is a matter for re-determination by appropriately qualified experts.
13. The orders made by the primary judge do not include any direction as to the outcome of the re-determination reflecting the conclusion stated at [70], and, accordingly, it is sufficient to note that I would grant leave to appeal but dismiss the appeal with costs.

Endnotes

1. at [36].
2. See Digest of Justinian, in Corpus Juris Civilis (Theodor Mommsen & Paul Krueger eds., 1880-95) (Digest), 9.2.2.pr
3. See Digest 9.2.27.5
4. See Digest 9.2.11.3 and Digest 9.2.51.
5. See Wolfgang Ernst, Justinian's Digest 9.2.51 in the Western Legal Canon: Roman Legal Thought and Modern Causality Concepts (2019, Intersentia Ltd).
6. See Baker v Willoughby [1970] AC 467 at 492.
7. See Busby v Morris [1980] 1 NSWLR 81 at [19].
8. See State Government Insurance Commission v Oakley (1990) 10 MVR 570; [1990] AustTorts Reports 81-003, p. 67, and 57.
9. See primary decision at [36]. DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated. Decision last updated: 20 December 2019