Ripping yarns

THE EXPERIMENTS by Smith and Chapman had surprised Professor Chaikin. He had described the tufts as the strongest evidence that the jumpsuit had been cut — a fact which he had believed proved that the damage had been caused by a dingo. Now the main basis for his damning evidence at the trial had been torn away.

Faced with this new evidence, he formed a new theory, suggesting that dingoes’ teeth could not produce ‘snippets’, which he explained were very short tufts of nylon. Again, however, he was surprised. Dingoes in controlled experiments proceeded to produce not only tufts, but also snippets. This was confirmed by Raymond, and ultimately conceded by Chaikin himself.

But he was still undaunted, and subsequently proffered another new theory, suggesting that it was possible to distinguish between cuts caused by a sharp implements and cuts caused by carnassial teeth because only the former would result in an alignment of the severed ends of the fibres in what he called a ‘planar array’. He variously defined this concept as a deviation in the ‘planarity’, or alignment of the cut ends of the fibres, limited to about ‘one-tenth or one-twentieth of a millimetre between the fibres, or two or three diameters’ difference … or just a coarse human hair difference’ and ... ‘well, you can have an approximation. In fact ... one or two hairs’ difference.’

In November 1986, he asked a colleague, Dr Griffith, to examine the jumpsuit. Dr Griffith accepted the concept of a planar array but defined it differently, insisting that it had to extend over a line at least five millimetres long, but suggesting that the degree of deviation could be as much as a whole yarn, which was about seven times the thickness of an individual fibre. The concept was also supported by Dr Robinson, the microscopist who had operated the scanning electron microscope when Chaikin first made his observations; but he too defined the concept differently, suggesting that the alignment had to be within the width of one fibre. There was also disagreement about the necessity for the alignment to be consistent, with Robinson maintaining that it had to be in a continuous sequence involving every fibre in a number of consecutive yarns, and Griffiths accepting that it could be intermittent.

On the other hand, the experiments conducted by Smith and Chapman had produced many samples in which cuts caused by dingoes were quite straight and, even when examined under an optical microscope, appeared to exhibit a planar array, as Chaikin, Griffin, and Robinson had variously defined it. They, in turn, insisted that one could determine the presence of a planar array only by examination under a scanning electron microscope which offered a considerably higher level of magnification and a greater depth of field. Smith and Chapman were not textile experts — though it seemed that no one but Professor Gustafson had carried out such an extensive program of experimentation — and Dr Bill Pelton, a Canadian textile expert working in Australia, was asked to review their findings. He found the cuts in the dingo-damaged samples to be remarkably similar to the cut in the collar of Azaria’s jumpsuit, and supported their conclusions. He also said that a scanning electron microscope was not necessarily the best means of examining the severed ends of the yarn. The degree of magnification was too great, one could only see one or two yarns at a time, and, since the cloth had to be wrapped around a stub, one could not sight along a flat line of severance. The angle at which the severed ends of the yarns were viewed could also be misleading, and that risk was increased by the depth of field, which sometimes gave the impression that two fibres were side by side when one was considerably lower than the other. With an optical microscope one could manipulate the sample at will and sight along the edges of the cut yarns. Reliance upon a scanning electron microscope also required one to work from a series of two-dimensional images — or ‘micrographs’, as they were known — pieced together to create a ‘montage’ to reveal the line of cut yarns.

Professor Randolph Bresee had come from Kansas to give evidence, and he immediately enchanted a young woman who met him in our legal room with his warm smile and booming assurance, ‘No need to be formal, little lady, you can call me Randy.’ He looked at me in puzzlement as she was reduced to almost sobbing with laughter.

He seemed even more puzzled by the assumption of the Australian experts that a dingo could not have caused a mixture of cuts and tears. He explained that in North America, damage of this kind had long been used as a criterion for distinguishing attacks by wolves, jackals, and other canids from attacks by bears, whose teeth produced only a tearing action. He and Professor Fernhead also agreed that an optical microscope offered at least an equally valid means of determining the planarity of the fibres.

Morling ultimately asked Porter to find an independent microscopist who could throw some light on this controversy — a task for which Dr Hoschke was duly recruited from the CSIRO. He said that the experts in his laboratory used scanning electron microscopes to study the severed ends of individual fibres but, when it came to determining the planarity of a line of severance, they normally went back to an optical microscope. He also said that whilst ‘planar array’ was an accepted concept, the term had been misused by the Crown experts. The concept actually involved an alignment of fibres within very fine tolerances. In order to achieve such planarity, CSIRO scientists went to the lengths of sharpening scissors under a scanning electron microscope to ensure that they were as sharp as human ingenuity could make them. A planar array in the accepted sense was not evident in the damage to Azaria’s jumpsuit. Indeed, one could not produce it in terry-towelling material, but only in fabric with a tight weave. Furthermore, he had never heard any expert suggest that the presence or absence of a planar array offered some means of distinguishing cuts caused in one manner from cuts caused in another.

Dr Robinson had produced montages for the purpose of illustrating the difference between a planar array caused by a scalpel and a mere straight cut caused by dingo teeth. But when these were examined by Dr Hoschke, he was not impressed; the scalpel cut was, he found, ‘less planar’ than the damage caused by dingo teeth.

Pelton agreed that the scalpel cut did not display a planar array, and Raymond said that if the term could be used to describe the damage in the ‘V’ cut to Azaria’s jumpsuit, he had also seen planar arrays in material damaged by dingoes. Professor Bresee also agreed that Chaikin’s third theory was unsustainable.

The Crown was driven to argue that the damaged ends of the yarns might have changed over time and that the observations made by Chaikin and Robinson in 1981 had established that the damage had been caused by a cutting instrument, even if that conclusion could no longer be verified. But Robinson had taken few notes and no photographs of what he had then seen and, since neither he nor Chaikin had realised that dingo teeth could cut, they had concentrated only upon distinguishing cutting from tearing. Photographs had been taken by Dr Brown, the dentist who had taken the clothing to London, and when those were compared with the current state of the damage, they revealed little change. Scissor cuts made when Dr Scott had removed a sample of the material for testing had also maintained the same degree of planarity since late 1980. Raymond said that the appearance of the ‘V’ cut in Brown’s photographs was not inconsistent with damage by a dingo. Furthermore, if Hoschke was correct, a planar array in the accepted sense could not have been present even in 1981 and could not, in any event, have provided a recognised means of determining how the cuts had been made.

The Crown also argued that the absence of detritus or biological fluid capable of binding the fibre ends together offered a significant indication that the ‘V’ cut in the collar of the jumpsuit had not been caused by a dingo. There were, however, two difficulties with this argument. First, there was evidence that the fibre ends in the ‘V’ cut had remained relatively straight because they had been bound together by detritus. As Pelton pointed out, the combination of compression and detritus was significant because it was what would have been expected from the shearing action of the carnassial teeth. Second, there were samples of dingo-damaged fabric apparently free from detritus. In fact, Dr Hoschke found that the montage of dingo-damaged fabric prepared by Dr Robertson also displayed no sign of it.

Another distinguishing feature was said to be a ‘classic scissor cut’. When fabric is cut by scissors, there will be some distortion of the individual fibres due to the thickness of the yarns; most will actually be broken rather than cut cleanly, though to the naked eye the yarn will appear to be cut rather than torn. However, a microscopist will pick up the occasional fibre-end that has been cut cleanly and shows signs of compression from both sides. These characteristics distinguish a classic scissor cut from a razor cut, which is characterised by a flat, uncompressed fibre-end marked by striations in the direction of the cut. A classic scissor cut had been found in the sleeve of Azaria’s jumpsuit. Robinson said that he had never seen a classic scissor cut in dingo-damaged fabric, and it was highly probable that one would never be found. However, Pelton and Hoschke both said that at least one was evident in Robinson’s own montage of dingo-damaged fabric.

The ‘V’ cut was of particular interest to Dr Sanson, a zoologist who had made an extensive study of the manner in which kangaroos and other macropods chew plant fibres. The other damage, he conceded, could well have been caused by a dingo, but he found it difficult to conceive of any mechanism by which the teeth of a canine could have caused the ‘V’ cut because it was more than 10 millimetres in length, which was the longest straight cut that he thought could be caused by a single bite. He dismissed the suggestion that it may have been caused by two successive bites or chews. However, he was not prepared to say it was impossible for a dingo to have caused even this cut.

Meanwhile, Dr Griffiths had formed a further theory that the cut in the collar had been made, not by scissors, but by a single stroke from a knife. He injected a note of drama into the textile evidence by carrying out demonstrations with a doll on his lap and the collar of a jumpsuit held in a folded position against the neck whilst he slashed a knife across the throat. A number of jumpsuits that had been damaged in earlier experiments displayed cuts which resembled, to varying degrees, the damage to Azaria’s jumpsuit. His experiments suggested that if the collar had coincidentally been folded in a particular way, the cuts in the collar could be aligned in a manner that could have been caused by a single knife stroke. He had not carried out any research into the nature of fabric damage likely to be caused by dingoes, but nonetheless said that he could see no other way it could have been produced. The cuts in Azaria’s jumpsuit were no longer said to be evidence of an attempt to simulate a dingo attack, but the legacy of a murder.

As Morling pointed out, this left even the Crown experts divided. Chaikin and Cocks had both suggested that the damage had been caused by scissors. Sims had conceded that the ‘V’ cut in the collar was the sort of damage that might have been expected from carnassial teeth, and that it would have been difficult to replicate it with scissors. Now Griffiths had suggested that it was not caused by scissors but by a knife. Winneke protested that the Crown case seemed to be dependent upon a selective use of the evidence:

Professor Chaikin and that doyen of South Australian forensic science, Mr Cocks, are applauded when they give evidence of scissor cuts, but ignored when Dr Griffiths’ brand-new Wiltshire Staysharp knife hypothesis is propounded. Dr Sanson, on the other hand, is applauded for his comments about the ‘V’ cut in the collar, but ignored when he concedes that the remainder of the damage to the jumpsuit may be consistent with damage by a dingo.

A similar approach seemed evident in the Crown’s approach to the evidence concerning the manner in which the ‘V’ cut might have been caused. It was suggested that the opinions of Smith and Chapman were of little value because they failed to resolve the ‘geometric problem’. They had demonstrated that dingoes could produce damage which corresponded to each feature in the ‘V’ cut, but had not demonstrated that they could produce the overall pattern. As Barker pointed out, to prove that a dingo could produce ten straight lines did not prove that it could produce a perfect star-shaped formation. On the other hand, when it came to Griffiths’ experiments, the Crown relied upon the ‘ingredients’ and suggested that the rest was within the range of ‘experimental possibilities’. Not only Sims but Professor Fernhead, Professor Gustafson, and Dr Orams all agreed that a dingo could have caused the damage. Chapman suggested one possible mechanism, which Sanson found unacceptable, and Professor Gustafson suggested a number of others, but added, ‘It’s a guess. As every opinion concerning this are guesses. No one has seen a dingo cutting [jumpsuit fabric] on the baby.’

There were further hurdles in the path of the knife theory. Griffiths had said that it would explain not only the ‘V’ cut in the collar, but also the damage to the sleeve. Yet the sleeve damage contained a classic scissor cut that would have required opposing forces like scissors or teeth coming together, and could not have been caused by a knife on a soft background. Hoschke had shown that a planar alignment could not be obtained by using a sharp knife on fabric stretched over even a moderately soft surface such as a newspaper on a table. Furthermore, when Pelton examined the samples which Griffith had produced, he found that they did not reproduce all of the features of the damage to the collar of Azaria’s jumpsuit, and contained a number of ‘points of dissimilarity’.

However, Pelton’s evidence did more than merely sink another already waterlogged plank in the Crown’s case. He had also carried out an extensive study of the samples damaged by dingoes in the experiments conducted by Smith and Chapman. He had found nothing dissimilar and twenty-eight points of similarity between dingo-damaged fabric and the damage in Azaria’s jumpsuit. Of those twenty-eight points, twelve would have been difficult to reproduce with scissors, and four would have been ‘very difficult, if not impossible’ to reproduce in that manner. He noted that even Sergeant Cocks, who had been armed with sharp curved scissors, a seemingly limitless supply of jumpsuits, and ample time to practise, had been unable to reproduce these features, despite having the original jumpsuit in front of him to use as a pattern.

Pelton suggested that one would have needed more than a pair of scissors because the damage was a mixture of cutting and tearing, and the yarns had been pulled in a manner which would have required the use of tweezers if caused by human hands. Furthermore, there had apparently been no studies on dingo-damaged fabric prior to Azaria’s disappearance, and neither he nor any other textile expert or odontologist in the world would have known what to expect. How could the Chamberlains have simulated such damage when they could not have known what it was likely to look like?

The Crown seemed to be reduced to suggesting that this weary and distraught couple sat up in their motel room in the early hours of the morning, ‘took a stab at it’ and, by the merest coincidence, produced nothing inconsistent with damage by a dingo but twenty-eight points of similarity, a feat that Cocks had been unable to replicate. Not surprisingly, Dr Pelton concluded that the damage was ‘highly unlikely’ to have been caused by human intervention, and ‘highly likely’ to have been caused by a dingo or dog.

Predictably enough, other experts disagreed. Robinson and Griffith saw little similarity, but Fernhead, Gufstafson, and Raymond all said that the damage to the jumpsuit was not inconsistent with dingo damage.

Indeed, the prevalence of disagreement amongst expert witnesses was one of the most striking features of this case. The scientific controversy had already led Dr Baxter to adapt Newton’s third law of motion and proclaim a new law of forensic science: for every opinion, there is an equal and opposite opinion.