72 As her Honour noted[39], Ashley, J. in Popovski agreed with the magistrate that the "the proper test" as to whether injury arose out of employment was that it be the real, the effective or the proximate cause of the injury[40]. His Honour was not, however, called on to consider whether the use of the definite article by Mason, J. was intended to deny compensation in cases where, in addition to employment, one or more additional factors might also have been real, effective or proximate causes.
73 In our view, neither Mason, J. nor Ashley, J. meant to propound a general rule that employment had to be either the sole or the dominant factor in causing the injury. Neither Favelle Mort nor Popovski directly raised that issue. In any case, it would be quite wrong to treat the words of Mason, J. as if they were statutory words. In Hegedis,[41] Ashley, J. accepted that, save for special factual situations, proof that employment was a significant contributing factor would generally also establish that the injury arose out of employment. That is significant because, in Popovski, Ashley, J. accepted that injury may be caused by more than one "significant contributing factor", and that employment may be a significant contributing factor even though other factors were more significant[42].
74 Counsel for the respondents sought to support the interpretation that employment must be the - rather than a - cause of injury, by reference to a number of decisions. Counsel cited passages from the judgment of Lord Sumner in Lancashire and Yorkshire Railway Co. v Highley[43], and of Viscount Haldane in _Thom v Sinclair[44],_where the word "the" was used. In neither instance was the question in issue whether employment had to be the sole or dominant cause of injury. Certainly, no such statement was made in Thom or Brooker. In any event, as counsel conceded, it is not difficult to find an equal number of instances where judges have spoken of "a" cause, when discussing causation[45].
75 It would be surprising indeed if, in stark contrast to common law negligence claims[46], the worker in making a claim under a no-fault compensation scheme had to prove that employment was the sole or dominant cause of injury. Such a requirement would not be taken to have been imposed unless the statutory provision clearly so stated.
76 Accordingly, the "arising out" test will be satisfied if the employment is shown to have been a cause of the injury. It is not necessary to show that the employment was either the sole or the dominant cause of the injury.
"A significant contributing factor"
77 The question arises whether, in a case such as this, in order to show that injury arose out of the employment, it is sufficient to establish that employment was a significant contributing factor in the injury.
78 As noted already, Ashley, J. in Popovski,[47] relied on what was said by Mason, J. in Favelle for the conclusion that injury "arising out of" employment imposed a different and more stringent requirement of causation than that imposed by the requirement that employment be "a significant contributing factor", although he said, in effect, that the potential for a different result, by virtue of that distinction, would be rare.
79 In Popovski,[48] the instances where proof that employment was a significant contributing factor might not be sufficient were identified by Ashley J as being those "factually exceptional cases" with which Favelle Mort, Thom and Brooker were concerned. His Honour postulated a worker being struck by lightning at his workplace.[49] (As we have seen, the same example was used by Viscount Haldane in Thom[50] and by Lord Atkin in Brooker[51].) Ashley, J. held that, under "old authorities", that might not constitute injury arising out of employment, if the worker was not in the particular place where the lightning bolt hit by virtue of performing his work. His employment nonetheless would be a significant contributing factor in the worker being at that spot. In our view, what Mason, J. said in Favelle Mort ought be confined to the limited cases - of which Popovski was perhaps one - to which his Honour intended it to apply.
80 If it can be shown that employment was a significant contributing factor, that will usually be sufficient to show that the injury was one "arising out of the employment." In particular, we find it difficult to imagine a case where psychological injury to a worker resulting from a traumatic confrontation with a supervisor would not constitute both injury "arising out of employment" under s.82(1) and injury "to which employment was a significant contributing factor." If there is a distinction between the two concepts, it is more theoretical than real in such circumstances. Thus, in the present case it would be sufficient to show that the psychiatric illness was a reaction to what was said by the supervisor. It would not matter that other factors also contributed to Z's claimed psychiatric illness, such as the refusal of the doctor to provide a certificate. The relevance of those other factors did not preclude the conclusion that the words and actions of the supervisor were causative of injury, such that the injury "arose out of" the employment.
81 The phrase "significant contributing factor" should not be treated as a proxy or substitute for the statutory "arising out of" test. After all, the "significant contributing factor" test has been removed from s.82(1) altogether, and its function in connection with that subsection should now be consigned to legislative history.[52] Otherwise, attention will continue to be focused - unnecessarily and inappropriately - on what is meant by the word "significant". Thus it was in the present case that her Honour adopted the view of Ashley J in Popovski, that "significant" meant "of considerable amount or effect". For the reasons we have given, that is one question of interpretation which no longer arises, and we accordingly express no view on it.
82 There is a single test to be applied under s.82(1) - the "arising out of" test. The test raises a question of causation. In a case such as the present, the test is satisfied if it can be shown, on the balance of probabilities, that an injury to the worker was caused by an act or omission of the employer (including any servant or agent of the employer). This causation question is to be approached, like any other causation question, as a matter of common sense.
83 For these reasons, grounds 1, 2, 4, 5 and 7 should also be upheld.
Ground 3
84 As noted earlier, this ground concerned the significance attributed by her Honour to the plaintiff's own psychological fragility. The relevant section of the reasons for judgment is in the following terms: