R v Xie (No 19)

HER HONOUR: After delivering judgment on 28 July 2015 (R v Xie (No 18) [2015] NSWSC 2129), the Crown advised that when Mr Goetz was recalled to continue his evidence in chief before the jury he proposed to ask him the following question:

The Crown indicated that he anticipated that Mr Goetz would say in answer to that question that, in addition to the number of alleles and their respective peak heights, the relative proportions of the alleles in the mixed contributor DNA profiles in Items 550 and 616 at each of the 20 loci generated by application of PowerPlex 21 were also similar, and the “most similar” as between Item 550 and the various crime scene samples he reviewed.

The Crown also advised that he also proposed to ask Mr Goetz the following further question:

Mr Turnbull’s primary submission was that the further evidence the Crown proposed to call from Mr Goetz was covered by my ruling.

In support of that submission, Mr Turnbull placed particular emphasis on the emails that were exchanged between Mr Goetz and the ODPP, also extracted in the judgment, where Mr Goetz was asked by the Crown to address the very questions he proposed to ask when Mr Goetz’s evidence resumed (set out above).

When addressing that question by return email, Mr Goetz said as follows:

After reviewing my judgment in light of the further questions the Crown proposed to ask Mr Goetz, it seemed to me that, quite apart from whether the further evidence infringed my previous ruling, unless Mr Goetz had undertaken casework analysis sufficient to express an opinion about comparative similarity, the evidence the Crown sought to elicit from him would not satisfy the test of admissibility under s 79 of the Evidence Act 1995 (NSW), and would be excluded for that reason.

The Crown submitted that Mr Goetz’s email had been misinterpreted and that what Mr Goetz was endeavouring to convey, as confirmed in conference with the Crown following receipt of the email, was that a DNA analyst would expect to see different proportions of DNA in mixed contributor samples found within the one crime scene because of the dynamics of what is commonly encountered in a bloodshed event, but that the degree of similarity he observed between Items 550 and 616 was more than what an analyst would normally expect to see where multiple samples from the same contributors at the one crime scene were analysed.

On the assumption that Mr Goetz’s statement of opinion was based on relevant training, study or experience, the Crown submitted his evidence as to the similarity in the relative proportion of alleles as a feature of the similarity he observed was probative not only for the reasons advanced and discussed in the earlier judgment, but because the Crown proposed to submit that the degree of similarity from Item 616 to Item 550 referable to that additional feature adds further weight to proof of the fact that the DNA in the blood of the deceased was transferred from the crime scene to the garage, the children being, on the Crown case, the last to be killed.

Although the Crown proposed to confine Mr Goetz’s evidence to his observation of this additional fact or feature of similarity between the two items as an “objective” fact or feature of the appearance of the profiles or their pattern, without him venturing any expression of opinion that the degree of similarity was “unusual”, “significant” or “high”, Mr Turnbull submitted that it was inherent in Dr Goetz’s observation that there was a “marked” degree of similarity in the relative contributor proportions which he had not previously encountered but which he could not scientifically quantify, and which I have previously held was not an opinion that either Mr Goetz or Dr Walsh were entitled to express for that reason.

Ultimately it was agreed that the appropriate way to test whether Mr Goetz could give this evidence in a way that did not infringe my earlier ruling (and in a way that properly met the test for admission as opinion evidence under s 79) was to permit the Crown to call evidence from him on the voir dire.

Mr Turnbull sought advance notice of what further evidence Mr Goetz might give on the voir dire in explanation or elaboration of the evidence that was comprehensively tested in the interlocutory hearing before Johnson J, being the basis upon which I had also been invited to rule on the admissibility of his evidence in my earlier judgment. The voir dire was adjourned to allow that to occur.

Mr Goetz ultimately gave evidence on the voir dire that whilst mixed contributor samples are frequently encountered in a crime scene, an analyst does not “routinely look at them and say they’re different or similar”. The analyst’s awareness of differences between samples is solely for the purpose of determining which of the profiles is identifiable and suitable for uploading to the database as a single source sample. He said “you cannot load mixtures to the database”. He said he has probably seen mixtures of two, three, four or five contributors but could say nothing further than having encountered them in practice, having always assumed that differences in the appearance of mixed contributor samples was accounted for by the differing amounts of blood or other biological fluids shed by either the victim or victims and any suspect or suspects at a crime scene.

In his dealing with the mixed contributor samples in this case, Mr Goetz made it clear in his evidence on the voir dire that he only focused on Item 616 (being one crime scene sample) which he compared with the profile generated from Item 550. (For that reason alone the questions the Crown proposed to ask him set out above were inadmissible. So much was acknowledged by the Crown.)

Mr Goetz also gave evidence that in undertaking that comparative exercise, although Item 616 was a slightly weaker sample than the sample from the garage, all of the alleles that were present in Item 616 were also present in Item 550. That variability was explained in the following way:

He then gave the following evidence:

After Mr Goetz had given evidence in chief, Mr Turnbull sought the opportunity to reflect upon his evidence and take advice from those advising him before he cross-examined. Mr Goetz returned the following day.

In advance of Mr Goetz returning to be cross-examined, the Crown further refined the questions he wished to ask Mr Goetz in the trial by focusing on the similarity Mr Goetz noted in the “proportions” of DNA in the profiles generated from Items 616 and 550, with a view to having him elaborate on what the Crown described as an objective fact or feature of similarity.

In essence, the Crown indicated he wished to elicit from Mr Goetz that there was not simply a similarity in the number of alleles and their relative peak heights (evidence he and Mr Walton have already given before the jury without objection), but a “correspondence” or a “similarity” in proportions of alleles found at each loci in each sample as an additional and discrete feature of the objective fact of similarity between the two mixed contributor profiles generated from the two items. The Crown submitted that this was not to elicit from him an opinion as to extent or degree of similarity between the two samples in any qualitative sense, as would offend my ruling, but a further feature of the objective fact of similarity in the same way that allele numbers and their peak heights are objectively similar.

To exemplify that observation, the Crown had Mr Goetz prepare a histographic representation in percentile terms of the proportions of alleles at each locus in each of the two samples. (Item 616B, being the more complete profile that was generated by Mr Walton, generating 63 alleles, was relied upon for comparative purposes as distinct from Item 616A, which generated 61 alleles.) The Crown intends to tender the histograph to further or better exemplify the proposition that the vast preponderance of alleles are in proportion with each other at each of the 20 loci.

When he was recalled, Mr Goetz gave further evidence in chief on the voir dire that his preparation of the histograph was based on the results of Mr Walton’s DNA testing and, in particular, the relative allele peak heights in two samples. He said that there was no subjective analysis involved in his reading of the relative peak heights or assessing the relative proportions of the different alleles at each locus, or in the production of the histographs. That said, he accepted in cross-examination that what is rendered pictorially in the histograph is the “degree of similarity between the two profiles”, which he has repeatedly described as “unusual”. He went on to say that he regarded the degree of similarity as “dramatic” and, that being the case, he accepted it necessarily raises the question as to why that degree of similarity presented. He also agreed in cross-examination that the pictorial representation or the diagrammatic representation reflects his interpretation of both similarity and, to an extent, some features of dissimilarity, between the two samples.

In further elaborating on the extent to which the histograph was informed by his subjective perspective, he said in answer to a question I asked:

He went on to say in the balance of that particular answer:

In cross-examination Mr Turnbull invited Mr Goetz to restate, in accordance with his evidence before Johnson J, that he is unable to quantify the significance of the similarities between the two profiles or, and in that exercise, to attach any mathematical weighting to the dissimilarities that were revealed. He also agreed that he had not, on any other occasion, been invited to, nor had he expressed an opinion about comparative similarities (or dissimilarities) between DNA mixtures involving multiple contributors, and that the normal course when called upon to express an opinion of that kind is to test a given hypothesis in a validated and disciplined scientific paradigm. I then asked the following question:

In identifying the “something” that is revealed in the comparative exercise Mr Goetz was invited to address, he went on to say there is a similarity, the degree to which he cannot expand upon and an explanation for which he is unaware.

In the result, he said “the most I would go to is that there is similarity between the two samples”. He was at all times concerned to emphasise that he does not mean to suggest the profiles are “the same” and also concerned, given what he understood to be the constraints to which he was subject by reason of my ruling, to steer clear of utilising any comparative expressions such as “match”, or “match by chance”, or qualitative expressions of the degree of similarity.

Mr Turnbull submitted that although it can be said that the histograph renders, in a pictorial way, the relative proportions of the different alleles at each locus in each sample, and even accepting that did not involve any subjective assessment or interpretation of the results of Mr Walton’s DNA profiling, the histograph does not simply “describe” the similarity between the two profiles and, in that sense, it is not “value-free”. He submitted both the graph and Mr Goetz’s evidence, even if only led from him vive voce, necessarily calls for an explanation of features of dissimilarity, which in turn brings into play questions of degree. Mr Turnbull submitted that it is the existence of a tension between similarity and dissimilarity which is revealed in the histograph itself, a tension which Mr Goetz has said (and repeatedly) he cannot resolve or describe “scientifically”, that breaches my previous ruling, even if it does not do so in terms.

Whilst there may be nothing more than a linguistic nuance between the objective fact of a similarity in appearance or pattern between the DNA profiles generated from the two items, and the degree to which they are similar or dissimilar involving qualitative reasoning, I am satisfied that to admit the further evidence of Mr Goetz runs the real risk, against which directions cannot protect, of a jury misusing both Mr Goetz’s evidence of a similarity in proportions of alleles and a representation of that feature of similarity pictorially in a way which will be productive of unfairness to the accused. The risk of a lay jury being unable to discern the difference between similarity of this highly esoteric kind and the DNA profiles from Items 550 and 616 being for all practical purposes “the same”, is amplified by imposing an unfair forensic challenge on Mr Turnbull as the cross-examiner to confine the testing of Mr Goetz to an admissible opinion as to the fact of similarity in circumstances where even he is at a loss to explain it without introducing his view that it was the degree of similarity that was “unusual” which is, as I see it, simply another way of remarking upon its significance.

Although the additional feature of similarity which has been the subject of further testing on the voir dire has probative value (perhaps even considerable probative value if it were subjected to a statistical weighting) being, on one view of it, an objective feature of similarity in the two profiles along with allele numbers and peak proportions, it is not evidence in that same category. Even imposing upon Mr Goetz the discipline of not descending into a commentary on the extent or degree of similarity, or a range of possible explanations for it, there is, in my view, a danger of unfair prejudice of the kind that I have identified and, accordingly, the further evidence the Crown proposes to call from Mr Goetz is disallowed.