(a) expert evidence
39In support of those defences, the respondents relied upon an expert report prepared by Professor Roger Byard, the holder of the Marks Chair of Pathology at the University of Adelaide. The applicants challenged the admissibility of the report and Professor Byard's oral evidence, but it was admitted, a ruling challenged on appeal.
40Professor Byard was asked whether the Babywedge product was "a potentially dangerous product which could harm or even kill babies"; whether sleep positioners had been linked to deaths of 12 (or more) infants in the United States, and whether Babywedge was relevantly similar to the products linked to such deaths, so that it could be said that the Babywedge product is of a type that has been linked to such deaths. He answered those questions affirmatively in a report dated 5 January 2013.
41There was (and could have been) no challenge to Professor Byard's qualifications as a forensic pathologist with a special expertise in sudden infant and childhood death. He stated in his report that he had "a particular interest in accidental infant/childhood suffocation and [had] conducted research in this area for over two decades". That research had "involved the assessment of many hundreds of infant death scenes and the identification of previously unrecognised hazards such as U-shaped pillows and mesh-sided cots": Report, p 3. By way of general comment, Professor Byard noted (p 4):
"The exact contribution of soft bedding to an increased risk of infant death from SIDS or from accidental asphyxia may never be precisely determined, however it is well recognized that soft material that can press against an infant's face and nose is potentially dangerous. Lethal effects may include simply smothering or blockage of the external air passages, accumulation and rebreathing of carbon dioxide, and overheating (by interfering with heat exchange by the face). ...
We have investigated many cases of SIDS and accidental asphyxia in infants in South Australia and have found that any sleeping arrangement that creates a trough that an infant can roll or slip into may present a problem, as this may predispose to death from possible suffocation."
42With respect to the Babywedge being a potentially dangerous product, Professor Byard stated (p 5):
"The Babywedge device consists of a soft sloping mattress with a bolster on each side. Unfortunately this creates several problems. If an infant has rolled into a position where the faced was pressed into the trough between the bolster and the mattress it is possible that asphyxial episode could occur from external airway obstruction due to cover of the mouth and face (ie smothering). In addition there could be rebreathing of exhaled air, a problem that has been demonstrated in infants sleeping on polystyrene cushions. Another problem may occur if an infant has rolled into a face-down position (prone), as this has a well-established increased risk of death due to SIDS. It may be that once in a prone position in this device that an infant would not be able to self-extricate. Very young infants tire very quickly when they are trying to lift their heads free of soft surfaces. Fabric also becomes much less permeable to air if an infant has vomited or regurgitated fluid on to it."
43This key passage in the report was criticised by the applicants on a number of grounds. First, it was pointed out that the Babywedge did not have a "soft" sloping mattress but rather a firm mattress. Secondly, it was said that the bolster being removable and attached by way of Velcro strips which were positioned perpendicularly to the bolsters, allowed a gap between the bolster and the mattress, rather than a "trough". Thirdly, unlike polystyrene, the Babywedge was manufactured from open textured foam which allowed for breathing. These elements, which were said to render the Babywedge different from other sleep positioners for babies, had not, the applicants noted, been tested by Professor Byard with respect to the applicants' product. On that basis they submitted that his report could not constitute an admissible expert opinion about the Babywedge; that is, although Professor Byard undoubtedly had specialised knowledge relevant to the general topic of SIDS and risks of suffocation, that knowledge did not qualify him in accordance with s 79 of the Evidence Act 1995 (NSW) to give an opinion on the risks associated specifically with the Babywedge.
44Because virtually the whole of Professor Byard's evidence, other than his written report, was elicited on the voir dire, it is convenient to refer to that evidence before dealing with its admissibility and the inferences which were properly to be drawn from it.
45So far as the first complaint noted above was concerned, Professor Byard accepted that the mat was firm not soft and was a suitable sleeping surface for a baby: Tcpt, p 239(38). With respect to the fact that the bolsters were detachable and that they did not create a continuous "trough" along the sides of the mattress, Professor Byard did not concede that the Babywedge was satisfactory. The cross-examination extended over several pages, particularly at Tcpt, pp 252-254:
"Q. ... I take it you didn't make any tests on Babywedge as to the likelihood or unlikelihood of a trough which could lead to suffocation?
A. The reason I didn't is it was an observation, I could see the trough and I know that troughs are dangerous.
Q. Yes, but surely an attached trough, sorry an attached bolster causing a trough would not be the same as an unattached bolster?
A. As I said I think we can't say that because when I look at the attachment, if a baby is in the trough and pushes this to one side because their face is there, it actually seals off on the other side, so I think that would need to be looked at.
Q. Need to be looked at, how do you mean?
A. I think if you were going to make an assertion that there is no - there is an airspace under it, you'll have to test it.
...
Q. ... [T]here are no measurements or detailed descriptions of the Babywedge in the report?
A. Well, the reason for that is I was really trying to go back to first principles because there are so many different devices. The first principles are that when you have bolsters and you have troughs and you have soft surfaces and you have cloth over foam these are all potential problems that can cause accidents and deaths. I didn't need the dimensions to actually make that statement.
...
Q. What I'm suggesting is that the bolsters on Babywedge do not cause a trough? ...
A. Well (indicated) yes, it does. It's in front of me; (indicated) there's a trough with the bolster.
Q. But a trough means, does it not, an unbroken U-shape or V-shape? If there's a gap that wouldn't be a trough. If there's a gap between the bolsters [and] the Babywedge mattress that would not be a tough?
A. I probably created this problem, your Honour, by using the term 'trough'. What I mean is somewhere a baby can be trapped where there can be [sic] an air accumulation, carbon dioxide accumulation, overheating, or pressure against the nose and mouth. And it doesn't take much pressure for some babies, for them to suffocate.
Q. There would no chance of suffocation if the baby could breathe between the bottom of the bolster and the top of the mattress?
A. Well, depends. I'm not convinced that that is actually a very good air passage. Also, the baby could easily be up against the bolster and bring up stomach contents because these kids do have reflux and that would make it really quite nasty, even if the baby's nose was stuck into this gap I still [think] it seals off because it presses down on the outside.
Q. But you've done no test to confirm that, have you?
A. Just purely observation of hundreds of death [scenes] and looking at this.
Q. The bolsters are to go under the arms, aren't they?
A. Yes they are. Well, that's my impression from the picture.
Q. Well then the head wouldn't be between the bolsters?
A. One of the interesting things about babies, your Honour, I've seen videos at meetings that paediatricians have taken and they move around in their beds more than I move around during the day. They're incredibly, particularly when they're five or six months, they are very able to actually move from one end of the cot to another. They're like possums going down small holes."
46The thrust of the cross-examination was not to demonstrate that the Babywedge was not a product within the class of sleep positioners said to have caused problems in the United States. Rather, the classification was accepted, but specific characteristics of the Babywedge were suggested as a basis for not considering it to be a potentially dangerous product. To the extent that the foam used in the product was said to be different from other similar devices and was permeable for a baby seeking to breathe through the material and the foam with its nose and mouth against them, the assertion was unsupported by admissible evidence. (Evidence sought to be led from the individual applicants to this effect was rejected.) So far as the means of affixing the bolsters was a point of difference from other products, Professor Byard explicitly did not accept the proposition. He noted that if the baby's face pressed against one side of the cylindrical bolster, it would tend to press the other side against the mattress, thus sealing the space which might otherwise be found between bolster and mattress. In the end, it was specifically put to Professor Byard that there was some baby products, including Babywedge, "that would not be potentially dangerous or the potential danger would be so minimal that they could be used with expectancy of safety by babies": Tcpt, p 260(25). Professor Byard responded that he could not say that the risk was "minimal" as he did not have the data. "All I can do", he continued, "is look at the device and say that there are structural problems with this that could result in infant death."