WERE THE APPELLANT'S INJURIES CAUSALLY RELATED TO THE ABSENCE OF THE NOGGIN?
50To answer this question, consideration needs to be given to the possible mechanics of the appellant's accident.
51As noted earlier, Mr Heathcote considered that the spaces between the joists when in position (that is, without displacement of the subject joist) were too small for a large man like the appellant to fall through. Neither of the other experts expressed a different view.
52As a result, it is likely that the appellant fell through an enlarged space between the subject joist and its neighbour, which was pre-existing or made by him stumbling. This gives rise to a number of questions.
53The first is whether the displacement of the northern end of the joist by about one metre to the position where the joist was later found, resting in part on the adjacent joist, could have occurred in the course of the incident, whatever that may have been, that led to the appellant's fall? Mr Dubos could not rule out completely that this may have been the case but was unable to describe the forces at work which might have led to that happening (see [33] above). Mr Cowling and Dr Heathcote thought otherwise (see [33] above). Their view accords with commonsense because it is not possible to understand how the appellant accidentally knocking or tripping over the subject joist, being 34 kilograms in weight, could have caused its northern end to jump up one metre and land with its central part resting on an adjacent joist. Consistently with this view, the primary judge held that it is unlikely that this displacement of the joist occurred during the accident (Judgment [56] quoted in [39] above).
54The next question is whether some lesser displacement of the subject joist may have occurred in the course of the appellant's accident, with the remainder of the displacement occurring subsequently as a result of someone lifting it and resting it on the adjoining joist. Dr Heathcote suggested that this lesser displacement might have occurred as a result of the subject joist rotating whilst still resting on the wall plates. This theory seems to have involved the notion that, because the joists were much narrower than they were high, a tripping over or knocking of the joist by the appellant may have caused the top of the joist to fall over to the west (where there was no noggin to prevent it doing so). Mr Dubos did not refer to this theory and Mr Cowling rejected it as inconsistent with the fact that the southern end of the joist was still found to be skew-nailed in an upright position to the southern wall plate (see [24] above). In the absence of the joist having any quite extraordinary flexibility, which was not in fact suggested to exist, the notion that the joist may have rotated as described by Dr Heathcote defies commonsense. On the appeal, counsel for the appellant was not able to give any sensible description of the means by which that may have occurred. It may be that Dr Heathcote's evidence is to be explained by him forgetting that the southern end of the joist remained fixed. In any event, there is an overriding difficulty with the theory as it is not easy to see how, even if it is correct, the gaps between the joists would have been enlarged to a sufficient extent to permit the appellant to fall through.
55Another possibility is that, regardless of whether there was rotation to any significant degree, the northern end of the subject joist moved laterally to the west along the wall plate. Relevant to this possibility is a dust-free area on the northern wall plate, corresponding to the area upon which the subject joist would have rested before its displacement, that was observed by the WorkCover inspectors. It is clearly visible in their photographs, particularly the photograph numbered 14. Whilst the area does appear to be wider than the joist, that difference is very small, indicating that the joist did not slide to any significant extent along the plate to create an opening large enough for the appellant to fall through. The result is that the only significant movement of the northern end of the joist can have been by lifting, as the possibility of it jumping up during the incident leading to the appellant's fall has been discounted already.
56As the probabilities suggest that the subject joist was lifted out of its position, the next question is whether that occurred before or after the appellant's accident. The evidence left the answer to this question in the realms of speculation.
57The appellant suggested in argument that the joist may have been lifted after the accident by one of the emergency workers to ensure that it did not fall on the appellant whilst he was still being treated below, or possibly even to facilitate his extrication from the laundry. The former seems unlikely as the lifting of the 34 kilogram joist from its resting place on the northern wall plate to a position resting on an adjoining joist would seem, whilst the stricken appellant was immediately below, to have been fraught with difficulty and danger. If the joist was not moved before the appellant's accident, it was still resting on the northern wall plate, so that leaving it untouched, or at least nudging it to ensure that it was fully on that plate, would seem to have been the far safer alternative.
58The appellant's other suggestion, concerning his extrication, suffers from the difficulty that there was a doorway from the laundry to the outside and there is no mention in the ambulance or police reports of extrication of the appellant by hauling him up, presumably by ropes, through the ceiling of the laundry, or of any attempt to do so.
59The overriding difficult with both suggestions is however that even if one is well-founded, the means by which there might have come to be an enlarged gap between the joists at the time of the accident is left unexplained.
60That leaves the possibility that the subject joist was placed to rest on its neighbour prior to the appellant's accident. This possibility cannot be ruled out. Although Mr McWilliams said that he would have noticed if it had occurred before he left the site at about 9.00 am on 12 February 2004, he may have been mistaken. There was evidence that tradespeople had recently been removing render from a wall in the kitchen area and it is conceivable that they moved the joist to enable containers of waste to be lowered to the laundry level. As well, the possibility that the appellant, for some unexplained reason, moved the joist prior to his accident cannot be entirely discounted.
61The upshot of these considerations is that, as the primary judge found, the evidence did not enable the means by which the appellant's accident occurred, or its causes, to be determined. Whilst it was not essential for the appellant's success that the precise cause of his accident be demonstrated, he nevertheless needed to demonstrate that his accident, and therefore his injuries, resulted from Mr Rudd's assumed negligence in leaving one noggin missing (Kuhl v Zurich Financial Services Australia Ltd [2011] HCA 11; 243 CLR 361 at [50] - [54]). I turn then to consider whether that was the case.
62If, contrary to the prevailing view of the experts, there was room for the appellant to fall through a space between the undisplaced joist and its neighbours, and he did so, that could not be regarded as causally related to the assumed act of negligence in leaving one noggin absent. The noggin would have played no role in the accident if it occurred in that fashion as that thesis assumes that the subject joist did not move.
63If the accident occurred as a result of the appellant knocking or tripping over the subject joist, and causing it to rotate or slide, the absent noggin would have been causally relevant but, for reasons I have given, those are not realistic possibilities.
64If the subject joist was moved to rest on the adjoining joist prior to the appellant's accident and the appellant fell through the enlarged gap thereby created, the absent noggin would not have had any causal relevance. In any event, the displaced joist would have been obvious, as it is in the WorkCover's inspectors' photographs, and have been an aspect of the building site with which the builder would have been entitled to assume that an experienced tradesperson would readily be able to cope.
65If the subject joist was moved to rest on its neighbour after the appellant's accident, the absent noggin would have been causally relevant if an enlarged gap was created by the joist rotating or sliding to the west. However, as I have said, the evidence indicated that these were not realistic possibilities.
66The result is that the evidence does not reveal any likely cause of the appellant's accident, much less a realistic one with which the absent noggin had any causal relation. At best for the appellant, the evidence gives rise to "conflicting inferences of equal degree of probability so that the choice between them is [a] mere matter of conjecture" (Jones v Dunkel [1959] HCA 8; 101 CLR 298 at 304 - 5 citing Bradshaw v McEwans Pty Ltd (1951) 217 ALR 1 at 5; see also Luxton v Vines [1952] HCA 19; 85 CLR 352 at 359 - 360 and Condos v Clycut Pty Ltd [2009] NSWCA 200 at [68]). In my view, there is no reasonable basis in the facts proved "for a definite conclusion affirmatively drawn" for a finding which would establish the appellant's claim (Jones v Dunkel at 305). This accords with the primary judge's conclusion at Judgment [63] (see [39] above).