Hirst v Sydney South West Area Health Service  NSWSC 664
135 The Defendant submitted that s 5E, when speaking of onus of proof, covered not only the legal onus of proof but also the evidentiary onus. Accordingly, the Defendant submitted, the principle in Watts v Rake has no application because that principle imposed an evidentiary onus on the Defendant to disentangle other causes of the Plaintiff’s injury.
136 Three cases in the Court of Appeal suggest that s 5E is concerned with legal onus. In Woolworths Limited v Strong  NSWCA 282 Campbell JA (with whom Handley AJA and Harrison J agreed) said this:
 I do not find the statutory background to section 5E useful in interpreting it. Its words are quite clear, and do not change the pre-existing law . That the Ipp Report makes clear that the reason for including the recommendation that became section 5E was to remind courts that they ought not overlook an important part of the law of negligence does not, it seems to me, have any bearing upon its meaning.
 I do not agree that section 5E shows that the type of reasoning in Shoeys case is no longer open. It was uncontentious in Shoeys that it was the plaintiff’s task to prove causation of damage (68,940 col 2 per Mahoney J, 68,944 col 1 per Handley JA, with whom Priestley JA agreed). Section 5E makes no difference to that. But it was, and still is, possible for a plaintiff to satisfy its onus of proving causation if the court can infer that it is more likely than not that the failure to exercise reasonable care and skill was a necessary condition of the particular harm that the plaintiff suffered. In Shoeys there was no evidence of precisely what the plaintiff had slipped on, merely that it caused “a wet spot” on the heel of her shoe, and that there were some type of green leaves like cauliflower or cabbage on the floor near where the plaintiff fell. Nor was there any evidence of how long the substance on which the plaintiff slipped had been there. It was purely a question of the inferences open, on the facts of that case, whether the plaintiff had discharged her onus of proof of causation. As Ipp JA showed in Flounders v Millar  NSWCA 238 at -, this is an acceptable method of establishing causation of damage under the common law. (emphasis added)
137 In Varga v Galea , a case to which the Civil Liability Act applied, McColl JA having noted the terms of s 5E which provided that the plaintiff always bore the onus of proving, on the balance of probabilities, any fact relevant to causation, said:
 A defendant who alleges that a plaintiff suffered from a pre-existing condition which may have had an adverse impact on his or her future whether or not the immediate injury in question had occurred, bears an evidential burden to show that the plaintiff’s condition would have deteriorated in any event regardless of the accident: Watts v Rake  HCA 58; (1960) 108 CLR 158 (at 160); see also Purkess v Crittenden  HCA 34; (1965) 114 CLR 164 (at 168). As Ipp JA explained in Seltsam Pty Ltd v Ghaleb in a passage upon which the respondent relied, the effect of the High Court’s decision in Malec v JC Hutton Pty Ltd (1990) 169 CLR 638 is that because the issue involves “hypothetical situations of the past, future effects of physical injury or degeneration, and the chance of future or hypothetical events occurring … the Court is required to evaluate possibilities … not proof on the balance of probabilities.” (emphasis in original) : Seltsam (at ). Ipp JA then said:
“ Appropriate allowances must be made for these contingencies. A proper assessment of damages requires the making of a judgment as to the economic and other consequences which might have been caused by a worsening of a pre-existing condition, had the plaintiff not been injured by the defendant’s negligence. A pre-existing condition proved to have possible ongoing harmful consequences (capable of reasonable definition) to the plaintiff, even without any negligent conduct on the part of the defendant, cannot be disregarded in arriving at proper compensation.
 As was pointed out in Newell v Lucas [1964-5] NSWR 1597 (at 1601 per Walsh J, with whose judgment Hardie and Asprey JJ agreed), the court must determine whether a comparison may be made between the plaintiff’s condition prior to the injuries sustained by the defendant’s negligence (including the plaintiff’s economic and other prospects in that condition) and the plaintiff’s condition and prospects after the injuries. Nothing in Watts v Rake and Purkess v Crittenden precludes the judge from carrying out this exercise.
 Of course, if the evidence does not adequately establish the pre-existing condition or its possible consequences … it would not be possible to carry out such a comparison and assessment. In regard to the possible consequences, a scintilla of evidence would not suffice. The evidence must be such that a reasonable person could draw from it the inference that the possible consequences contended for by the defendant existed (see McCormick, Evidence , 5th ed, para 338, p511).”
138 Similarly, in State of New South Wales v Doherty  NSWCA 225, a case also governed by the Civil Liability Act , Hodgson JA (with whom Whealy JA and Handley AJA agreed) discussed a submission by the Plaintiff’s counsel concerning the evidentiary onus on the Defendant to disentangle the causes of the Plaintiff’s condition at  and went on to say at  that he did not think it was a case where the Defendant had failed to discharge an evidentiary onus, as in Watts v Rake or Purkess v Crittenden. It does not appear that s 5E was referred to.
139 I do not overlook the remarks of Allsop P (with whom Young JA agreed) in Zanner v Zanner  NSWCA 343 at  and  where he suggested that s 5E changed the common law. However, the issue in that case was principally the scope of liability issue raised by s 5D(1)(b) CLA , and the principal judgment of Tobias JA does not refer to s 5E. The precise standing now of Watts v Rake and Purkess v Crittenden awaits an authoritative decision of the Court of Appeal – Woolworths Limited v Strong does not say anything about those cases when discussing s 5E. In Varga the issue was not whether the issue referred to in s 5E was only the legal onus or also included an evidentiary one. The Court of Appeal appears, however, to have proceeded on the assumption that it referred only to the legal onus. Nevertheless, as a single judge I feel bound to follow the clear statements in Woolworths Limited v Strongin relation to s 5E, and the assumption in the approach of the Court in Varga .
140 As a matter of practicality it is likely that the reference to onus of proof in s 5E is a reference to the legal onus of proof. That is because the evidentiary onus shifts between the parties at various times during the case depending on what evidence is led by the other party.
141 Moreover, it does not appear from anything said in the Ipp Report (particularly para 7.26 – 7.49) that the issue being discussed was the principle in Watts v Rake . Nor does the discussion in such cases as Flounders v Millar  NSWCA 238 and all of the cases referred to therein, particularly in the judgment of Ipp JA, suggest that 5E is concerned with the Watts v Rake principle. The concern in Flounders and the cases referred to was the relationship between breach of duty, a risk of injury and the risk coming home. The present concern is at one stage beyond that, where causation has been established between the breach and some damage, and the problem is to decide what particular damage flows from that breach and what damage is occasioned by other factors. Whilst it is certainly true that the extent of the damage caused by the breach includes “fact[s] relevant to the issue of causation” it does not appear that the present issue was the one contemplated by s 5E.
142 Accordingly, in my opinion, the principle in Watts v Rake applies notwithstanding s 5E.