By Rod Cross, Physics Department, Sydney University. 



In November 2008, Caroline Byrne’s boyfriend was found guilty of throwing her off a cliff at The Gap in Watson’s Bay. Some of the forensic evidence presented at his trial can be found in the Journal of Forensic Sciences (2006) article .



On 24th February 2012, three judges of the NSW Supreme Court acquitted the boyfriend. They concluded that the trial miscarried because the evidence was weak and largely circumstantial, the prosecutor overstated the case and that my evidence as an expert witness was flawed. As a result, they concluded that the charge of murder was not proven beyond reasonable doubt. The judgement was summarised in a 252 page document released on the day of the decision. It is a public document containing material that is strongly critical of my role as a scientist in the case. My comments on the judgement were subsequently published in the Australian Journal of Forensic Sciences, Issue 4, 2014.


The decision highlighted a fundamental flaw in the legal system. The flaw involves the double standard whereby judges can pass judgement on matters outside their area of expertise, whereas experts are not permitted to comment on matters outside their area of expertise. My own view is that matters of science are best left to scientists to resolve, without interference from others, especially in the first instance. However, I was told by a senior barrister that if judges were required to have qualifications in fields on which they pass judgement then the whole legal system would collapse.



The following specific examples from the judgement illustrate some of the many instances where the judges used their higher authority to prove that I got it wrong. In all, I counted 170 factual mistakes made by the appeal judges. That was just concerning my own evidence. There were too many to include them all in this brief summary.


1. When Caroline Byrne landed at the bottom of the cliff she ended up with her legs pointing approximately to the west or north west. I worked out from the nearest points to the cliff, plus other factors, that she came from a ledge to the north. The judges dismissed that evidence, saying that she must have come from the direction where her legs were pointing. They ignored the fact that she landed at 80 km/hr.




          Photo taken from the north ledge showing a mannequin in the position that Ms Byrne landed.

          The mannequin’s legs are not pointing straight to the north ledge but are angled slightly away.

          The judges said that Ms Byrne must therefore have come from a point further around the cliff top

          and that I deliberately ignored the leg position. I ignored it because it was of no scientific value at all.


2. I conducted a throwing test where the woman who was thrown remained limp, to simulate the effect of throwing an unconscious woman. The judges dismissed that experiment as being ineffective because the woman "facilitated her entry into the water" by thrusting her arms forward. However, she did that AFTER she was thrown. Throw speed has nothing to do with what happens AFTER the throw. The woman even climbed out of the pool by herself, after the throw.


The chief judge commented that  To my mind all of this experimental analysis must be approached with considerable reservation. The tests carried out by A/Prof Cross were all conducted in daylight and in conditions where none of the participants had reason to fear for their safety. The run up was secure and the persons who were thrown were of course cooperative. One test was done where the female volunteer was asked to remain limp. However, even in this experiment she cooperated and facilitated her safe entry into the water.”



3. The judges preferred the evidence of the defence expert because he used "more sophisticated" equipment. They ignored the fact that his two subjects could apparently run almost as fast as the world champion sprinter "Flo Jo" from the 1980's. They failed to notice that he tested very good athletes, not females of average athletic ability, and they failed to recognise that a feet first jump results in a feet first landing, not a head first landing. Despite those serious omissions, the judge declared that “I am in no doubt that, because of the sophistication of his equipment, the tests conducted by [the defence expert] are more reliable.



The judges also concluded that I “conducted a series of not particularly sophisticated experiments” that “involved strong men throwing women into swimming pools”. Given the uncertainty of the athletic ability of Ms Byrne and the wide range of athletic abilities of other females, it was not necessary to measure throw or jump or dive speeds to an accuracy better than about 2%. The equipment I used was perfectly adequate for that purpose and cannot be criticised as being unsophisticated. Furthermore, the experiments themselves did not need to be sophisticated. They were designed to measure typical run, jump, dive and throw speeds and to establish reasonable limits of performance in those tests. The judges made several errors of fact here. Only one woman was thrown, not several different “women”. And many more experiments were conducted to measure running, jumping and diving speeds.



4. The judges didn't like my jumping and throwing experiments because "the conditions under which his experiments were conducted were materially different to the conditions on the night Ms Byrne died." The logical conclusion is that I should actually have thrown women off the cliff on a cold, dark night. They did not consider the fact that a cold, dark night would reduce athletic performance rather than enhance it.


5. The judges claimed that “A/Prof Cross was satisfied that a strong, fit man could have thrown a woman of Ms Byrne’s weight from near the bend in the safety fence.” I never made that claim. In fact, I found that throwers were able to throw at sufficient speed by taking a few steps before throwing to avoid going over the edge themselves. Had they taken a long runup from the safety fence then they may have gone over the edge.


6. After I submitted my first report on the case, I asked the police if they were certain that they had given me the correct landing spot and I asked for photos of the landing spot since I had difficulty understanding the surprising lack of injuries sustained in the fall. The police followed up by arranging a visit to the site to help sort out those concerns. The judges agreed that this was an example of me “actively participating in the making of evidence directed to traversing of the existing forensic evidence which as a consequence caused the trial to miscarry.”  Scientists always double check and retrace their steps in an attempt to ensure that their results are valid. The judges and the defence should have been well aware of that. If not, then it discloses deep ignorance of the way that scientists undertake their work.


Nevertheless, the judges concluded that  “By the time he was able to revisit the site, A/Prof Cross had become involved and was questioning whether the correct location had been identified. A/Prof Cross’ reasoning for doing so appears to have no foundation other than perhaps out of concern to eliminate the possibility of suicide, thus leaving open a prosecution for murder.”


7. Another physics mistake concerned the evidence that everyone gave that the night was pitch black. The judges said that in that case, nobody would run and throw a woman off the cliff because it would be too dangerous. I checked the weather records and found it was cloudless on the night and the moon set at 1 am. A scream was heard at 11:30 pm. People started arriving aftert 2 am. The judges either ignored that evidence or were unaware of it, and obviously didn't bother to check themselves. It didn't rate a mention in their 250 page report. That is one of the first things I checked. There were two fisherman who arrived at about 10 pm and also said it was very dark. They were fishing near a street light about 200 m away. They were the ones who heard the scream.  You can't see the ground very well or even the stars if you are near a street light. If you move away from the light so it is hidden then the ground is easy to see if the moon is up and the eyes get accustomed to the dark.


8. The judges claimed that I “set about determining whether she could have been thrown from the cliff.”  That conclusion was incorrect. My objective was to examine all the evidence to see if it pointed to an accident or a suicide or a homicide, or indeed whether insufficient evidence was available to make any such determination. My first quick calculation in 1997 indicated that Ms Byrne had jumped. In 2003, having performed some preliminary throwing and jumping experiments, I came to the same conclusion. It was not until 2005, after many additional experiments, that I concluded that she was thrown.


9.  It was claimed that “However, he calculated that with the available run up it was possible for a strong man, using a “spear throw” technique to have thrown Ms Byrne to hole A without also falling off the cliff top as he threw her.”


There are several factual errors in that sentence. The available runup was more than sufficient to take a few steps. The available runup did not therefore limit the possible throw speed. Furthermore, the danger of falling off the edge was not a theoretical calculation. It was based on the experimental evidence.



10.  The judges noted that  “In 2003, in a walk-through interview with police, eight years after the event, Peter said that the applicant was pointing in the direction of Pyramid Rock. That evidence is somewhat troubling. If as all the evidence indicates it was a “pitch black” night and the rocks could not be seen from the cliff top it would have been difficult, if not impossible, to determine that the applicant was pointing to pyramid rock.”


That is illogical and naēve. Peter (Caroline’s brother) was with Caroline’s boyfriend at the time. He could see where the boyfriend was pointing. He couldn’t see the rocks below. But when he went back later, he could see the general area to where he was pointing. The most obvious feature in that area is the Pyramid Rock. So, one can assume that Peter told others later that the boyfriend was pointing toward the Pyramid Rock.



11. The judges commented that “A/Prof Cross said that he had concluded that the “running speed” for 13 females aged 20 to 35 years after they had run 4 m ranged from 3.7-4.85 m/sec. In his experiments one of the women tested would have achieved the speed to dive to hole A. However, A/Prof Cross said that none of the police cadets could have jumped to hole A.”


In fact, it was the other way around. That is, none of the cadets could have dived to hole A. The judges failed to understand the significance of the results, and thereby got it wrong. It is quite a serious mistake, given that Ms Byrne landed head first.


12. The judges commented that I have “no qualifications or experience in biomechanics.”


That is not correct. I have no formal qualifications in biomechanics, but have had considerable experience working with biomechanists regarding sports research. We have published joint papers. I have refereed many papers on biomechanics for journal editors. Biomechanics is a field based on mechanics, which is properly a field of physics. In any case, my measurements were simply those of running, jumping, diving and throwing speeds, which can easily be obtained by standard video analysis or radar gun measurements, commonly used by both physicists and biomechanists. I even conducted a few measurements using a ruler, despite my formal lack of qualifications in biomechanics.


13. The judges commented that “Prof Fryer concluded that Ms Byrne’s shoulder width ranged from 342 mm to 353 mm, most probably 345 mm”


The judges then quoted from my own report:


 “The width of a female across the shoulders is typically about 40 to 43 cm, while the incorrect cavity is about 40 cm wide at the top and narrows to about 30cm at the bottom.’ A/Prof Cross’s assumption was clearly wrong. It casts considerable doubt, at least on this aspect of A/Prof Cross’s thesis.”


I measured the shoulder widths of 16 females and they ranged from 350 mm to 390 mm with both arms up, and from 390 mm to 450 mm with both arms down, as detailed in my report of 4 April 2008. Prof Fryer did not include the the full width of the shoulders and both arms in his estimates of shoulder widths.  The judges effectively concluded that Ms Byrne did not have any arms, hence Prof Fryer was correct and I got it wrong.


The judges missed or misunderstood the whole point. That is, why were there no injuries to Ms Byrne’s shoulders given that hole B was 1 m deep and narrowed to 300 mm at the base? Ms Byrne was wedged about 1 m deep up to her waist. The answer is that she didn’t land in hole B. All the physical evidence, including the dimensions of hole B, pointed to the fact that hole A was the correct landing point. That evidence was presented to the jury at the trial. The judges ignored all that evidence in their report and claimed that there was still some doubt.


The judges also commented on the mannequin that was used. The mannequin could not fit firmly in hole B unless both arms were removed, reducing the shoulder width from 365 mm to 330 mm. The judges overlooked that detail in coming to their conclusions.