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The main contributing factor test where causation is multifactorial

  • Newsletter Article
  • Published 19.03.2024

BGV v Waverley Council (NSWPICPD 2024)

Link to Decision

Link to Video

Key Takeaways

  1. The ‘main contributing factor’ test is not purely a medical question but involves an evaluative process, considering the overall evidence relating to causal factors to the aggravation both work and non-work related.
  2. The onus of satisfying the statutory test of injury in s4(b)(ii) where causation of an ‘aggravation etc’ is multifactorial is on the worker.

Brief Facts

The worker, BGV, worked with Waverly Council (the employer) from November 1997.

The worker alleged various occasions of bullying and harassment by work colleagues, abuse based on her gender and sexual orientation and an issue regarding the availability of toilet facilities for female employees leading to a complaint to the Anti-Discrimination Board. The worker notes an occasion in which she found a deceased woman at North Bondi beach, for which she did not receive any counselling or emotional support.

The worker lodged a claim for psychological injury against the employer. The insurer denied liability, essentially denying the occurrence of ‘injury’, on account of the worker’s diagnosis of cervical cancer and relationship breakdown around the time in which she alleges workplace issues.

The worker lodged an ARD, where the matter proceeded to a conciliation/arbitration. Following two days of submissions, the Member issued a Certificate of Determination in favour of the insurer, indicating that:

  • the causes of the deterioration in the worker’s condition were ‘complex and multifactorial’.
  • The Member was not satisfied that employment was the main contributing factor to the aggravation of the worker’s underlying condition.

The worker appealed the Member’s decision. Deputy President Michael Snell (DP Snell) addressed three grounds of appeal:

  1. The Member misdirected himself regarding the test for causation of injury.
  2. The Member erred in finding that the evidence did not demonstrate that work was the main contributing factor.
  3. The Member failed to give adequate reasons.


The worker argued that it is sufficient if there was, even in small part, an aggravation mainly caused by work and that the totality of the pathology does not need to be mainly caused by work. It was argued that this view was consistent with the authority of AV v AW (NSWWCCPD 2020), in which DP Snell presided. The worker referred to DP Snell’s remarks in that decision:

“... if there is multifactorial causation, a member must evaluate the causative role of each such factor ... this does not permit speculation by a member that a factual circumstance in a worker’s life might be causative of psychiatric injury, much less that it is causative to any particular extent. Causation of injury, and apportionment thereof in a psychiatric case is a matter where factual findings must (almost) always be anchored to expert opinion.”

The worker submitted that the Member at first instance erred in referring to ‘a number of non-work-related factors’, which the Member described as ‘stressors’. The worker said that whether a negative or unpleasant human experience is a stressor in a causation-sense is a matter purely medical in nature. It was also submitted that judicial notice could be taken that all members of society suffer from the vicissitudes of life but not all are adversely psychiatrically impacted by this, and to the extent they are, that is only provable medically and not speculatively by a lay person.

DP Snell rejected this ground of appeal.

DP Snell indicated that in AV v AW it was said that the test for ‘the main contributing factor’ is one of causation and involves consideration of the evidence overall (it is not purely a medical question). He noted that it involves an evaluative process, considering the causal factors to the aggravation both work and non-work-related. This leads to the understanding that the absence of medical evidence to address the ultimate question of main contributing factor is not necessarily fatal, as satisfaction of the test is to be considered on the whole of the evidence.

In respect to the second ground of appeal, the worker argued that, consistent with the authority of Watts v Rake (HCA 1960); 108 CLR 158, if the insurer wishes to disentangle causation in a multifactorial case then it carries the onus in that respect.

DP Snell indicated that the authority of Watts dealt with the shift of the burden of proof where the worker has made out a prima facie case that incapacity has resulted from the defendant’s negligence, which then shifts the onus of adducing evidence that the worker’s incapacity is the result of some pre-existing condition or that incapacity would have resulted from a pre-existing condition, onto the defendant.

DP Snell confirmed the test of ‘main contributing factor’ in s4(b)(ii) does not relate to pre-existing conditions. The present case involved satisfaction of the statutory test of injury in s4(b)(ii) where causation of an ‘aggravation etc’ is multifactorial. Accordingly, DP Snell did not accept the submission that Watts could be properly applied in determining whether the worker had discharged her onus of proving ‘injury’ within the meaning of s4(b)(ii) and ultimately accepted the insurer’s submission that the worker carried the onus of proving ‘injury’ within the meaning of s4(b)(ii): “he who asserts must prove” (see Commonwealth v Muratore (HCA 1978); 141 CLR 296).

DP Snell rejected this ground of appeal and, after confirming the third ground of appeal failed, noted that the appeal failed.


This case highlights the difficulties in determining the main contributing factor to a worker’s psychological injury. In many cases, workers present with multiple stressors coinciding with various workplace events that are alleged to be the main contributing factor to the contraction of a psychological condition. One must have regard to the relevant authorities dealing with the statutory test under s4(b)(ii) which confirm that the test is not purely a medical question but requires an evaluative test. Additionally, even in the circumstance that the defendant argues that causation for the psychological injury is multifactorial and that the non-work-related stressors are the main contributing factor, the burden of proof remains with the asserting party to prove its case; i.e. the worker.