Using common sense to evaluate the causal chain

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By Patrick Walsh, Partner

The Supreme Court of South Australia Court of Appeal in its decision in Return to Work Corporation (SA) v English; Williams v Return to Work Corporation (SA) [2023] SASCA 125 has “doubled down” on the evaluative test set out in Return to Work Corporation (SA) v Summerfield (2021) 138 SASR 175 in its latest decision concerning the moveable feast that is permanent impairment assessments under the Return to Work Act 2014 (SA) (the RTW Act).

This decision of the Court of Appeal is a much-anticipated instalment in a series of decisions concerning the manner in which impairments can be combined pursuant to sections 22, 56, and 58 of the RTW Act.  The outcome of the decision, in combination with the amendments to the RTW Act by the Return to Work (Scheme Sustainability) Amendment Act 2022 (SA) (the Scheme Sustainability Amendment Act), is such that it seems unlikely that there will be any further appeals on this issue to the Court of Appeal; but this will remain a much-litigated feature of the scheme for the foreseeable future in the absence of legislative reform.


The assessment of any permanent impairment is one of, if not the most, contentious aspects of the current scheme.  This is because it serves as the means by which an injured worker establishes:

  1. Whether they are entitled to any lump sum payments pursuant to sections 56 and 58 of the RTW Act (as an injured worker has to have a whole person impairment of 5% or greater).
  2. The extent of any entitlement to lump sum compensation pursuant to sections 56 and 58 of the RTW Act. In this regard, it is important to understand that section 56 operates in such a way that the entitlement significantly escalates as the assessment approaches 35% whole person impairment.  By way of illustrating this point, the difference in the scheduled sums for 2023 are:
    1. 5% to 14% – $84,963;
    2. 15% to 24% – $168,963; and
    3. 25% to 35% – $238,355.
  3. Whether a worker is a seriously injured worker for the purposes of the RTW Act and therefore has an entitlement to, amongst other things, weekly payments to retiring age and medical and like expenses for life.

Under the now repealed Workers Rehabilitation and Compensation Act 1986 (SA) (the WRC Act) the lead decision on the method by which impairments were combined for the purpose of determining whole person impairment was Marrone v Employers Mutual Limited (2013) 116 SASR 501.  The decision of the Supreme Court of South Australia Full Court in Marrone concerned that combination of impairments arising from the same trauma.  This required that the relevant impairments arise from the same event, or series of events, in order to be combined.  As such an injured worker was not able to combine impairments in circumstances where the impairments did not arise from the same sequence of events; as is the case with most consequential injuries.

Prior to the Scheme Sustainability Act, the RTW Act retained the “same trauma” test for the purpose of combining impairments for the purposes of sections 56 and 58 of the RTW Act but introduced a new test for combination of impairments in section 22(8)(c), which stated that “impairments from the same injury or cause are to be assessed together or combined to determine the impairment of the worker”.  It is the test set out in section 22(8)(c) of the RTW Act that has lead to the series of appeals to the Full Court and Court of Appeal.

Prior to the Court of Appeal’s decision in English being published the Scheme Sustainability Amendment Act amended sections 56 and 58 of the RTW Act to remove the reference to “same trauma” and state that impairments arising from the same injury or cause are to be assessed together and combined.  This almost brings those sections into conformity with subsection 22(8)(c) of the RTW Act which states that impairments arising from the same injury or cause are to be assessed together or combined.

Facts in English and Williams

Helpfully, Doyle JA in his reasons sets out succinctly the relevant facts in respect of the impairments in English stating at paragraph 150:

  1. Mr English suffered a neck injury on 4 March 2019, as a result of a falling rope line hitting and pinning him, causing an impairment of his neck.
  2. He was prescribed, and ingested, high doses of the drug Lyrica in order to treat neuropathic pain caused by his neck injury.
  3. His ingestion of Lyrica on 10 May 2019 caused him to feel lightheaded and to fall over.
  4. The fall resulted in the injury to his right quadriceps, and hence the impairment to his right quadriceps.

In respect of the impairments sustained by the worker in Williams, his Honour Justice Doyle placed importance on the findings of Deputy President Judge Rossi that the injury to the worker’s right knee had been caused by work activity from early May 2015 and that the injury to the left knee was caused by the same work activity over the same period.  His Honour went on to cite Rossi DPJ’s findings “that “the sole cause” of both of the 2015 knee injuries was “the work activity involving the climbing of ladders and steps and the working in a crouched position from early May 2015 until August 2015.  There is no “relevant external causal event.”


His Honour Justice Doyle states in his reasons:

The legislative text requires that the impairments be “from the same injury or cause”.  Whilst the requirement that the impairments be “from the same … cause” must have some limits, I see no basis in any of these words for confining the combination of impairments to circumstances where the later impairment involves a direct physiological consequence of an earlier injury without the involvement of any additional event(s) other than what might be regarded as the ordinary activities of life.  The words “from” and “cause” are inherently broader, and more flexible, than this.” per 136

In my view, it is neither possible nor appropriate to be any more prescriptive than Stanley J was in Summerfield.  In determining whether impairments are to be combined under s 22(8)(c) in assessing an injured worker’s WPI, the issue is whether the impairments are “from the same injury or cause”.  In considering whether a later impairment qualifies for combination, it is necessary to consider the causal explanation for each of the impairments, in order to determine whether those explanations possess the requisite sameness.  This requires an evaluative assessment of the causal explanations, and in particular any differences between them.  It requires an evaluative assessment of whether any additional events or integers in the causal explanations are of a nature or significance that means the impairments cannot be said to arise from the same injury or cause.” per 139

The additional events are each the natural and foreseeable consequence of the preceding event.  The causal chain does not involve, let alone depend upon, any additional event which can be said, as a matter of common sense, to have undermined the directness of the causal chain between the events causing the first injury and the occurrence of the second injury and impairment.” per 155

Implications for Employers and Self-Insurers

As the Scheme Sustainability Amendment Act has now amended sections 56 and 58 of the RTW Act the “same trauma” test as set out in Marrone is of very little relevance to the current scheme.  It has been my experience that, even before these amendments, much of the focus has been on whether impairments ought to be combined as arising from the same injury or cause as these tests are broader than the “same trauma” test.

The “same injury” test is likely to remain a fairly straight forward exercise in that it requires an assessment of the available evidence to determine whether multiple impairments arise from the same injury.

The “same cause” test is likely to remain the more contentious method by which impairments may be combined.  As his Honour Justice Doyle concedes, such a test must have some limits, but it is difficult to articulate how this can be approached in a more objective sense.

Notwithstanding that fact that his Honour Justice Stanley specifically eschewed reliance on the common law test of causation in his reasons in Summerfield, I believe that it is helpful to consider the approach of his Honour Deputy President Judge Rossi’s in Donovan v SA Ambulance Service [2020] SAET 161.  At paragraph 74 of his reasons, his Honour cites McHugh J in Bennett v Minister of Community Welfare (1992) 176 CLR 408 who states:

“… the common law concept of common sense causation accepts that the chain of causation between breach and damage is broken for the purpose of attributing legal responsibility for that damage if there has been an intrusion of ‘a new cause which disturbs the sequence of events, something which can be described as either unreasonable or extraneous or extrinsic

His Honour Deputy President Judge Rossi went on to make some observations at paragraph 88 regarding the “same cause” test:

Causation for the purpose of s 22(8)(c) involves both factual and normative questions.  Section 22(8)(c) involves an evaluative judgement of the degree of connection between the impairments sought to be aggregated or combined in determining the liability of the compensating authority.”

The application of the chain of causation principle incorporates the maxim of novus actus interveniens.  Any impairment from injury arising from an intervening event is not caused by the initial injury and accordingly cannot be combined with an impairment from the initial injury.”


Effect is to be given to the combination of the two words “the same” in s 22(8)(c).  An impairment caused by an external event, even if it does not break the chain of causation, and is also an impairment from the initial injury, cannot be combined with an injury solely caused by the initial incident as the further impairment is not from the same cause.

Although it can be difficult to predict how an assessment of permanent impairment will proceed at the outset of a claim, the importance of being able to analyse any casual chains between the initial injury(ies) and any resulting permanent impairments will ensure that:

  1. adequate investigations being undertaken at the outset of any claim to establish whether there are any relevant pre-existing injury(ies) and/or impairment(s) and the factual circumstances giving rise to the work injury; and
  2. properly tracking the progress of each claim in order to be able to undertake an analysis of the casual chain between the initial injury(ies) and any resulting impairment(s),

will remain critical to ensuring claims pursuant to sections 22, 56, and 58 are properly determined.

For further information, please do not hesitate to contact us.

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