Thursday, August 14, 2014
More on expert evidence
Two decisions of the High Court of Australia yesterday don’t develop the law but they do illustrate how careful everyone should be about expert evidence.
Is the evidence based on specialised knowledge?
In Honeysett v The Queen  HCA 29 (13 August 2014) an expert was called to compare images of the offender obtained from CCTV footage with photographs of the defendant (appellant) taken at a police station. The expert noted some points of similarity. Although in the High Court the respondent suggested that this evidence was adduced only to show that the defendant “could not be excluded” as the offender, the reality was that at trial it had been advanced as supporting an inference of identity. The issue was whether the witness was giving expert testimony.
It seems obvious, now that we know the result, that this sort of comparison could be made by members of the jury for themselves; it did not require any expertise. The limited nature of the evidence in this case was such that it did not involve use of the witness’s expertise in anatomy. Also, the respondent resiled from what in the lower courts had been advanced as engaging expertise: the witness’s experience in viewing CCTV images and making comparisons with suspects; only expertise in anatomy was now relied on .
The non-engagment with the witness’s expertise was apparent from a passage in the court below (Macfarlan JA, with whom the other members of the NSW CCA agreed, in upholding the conviction), and quoted by the High Court at :
“In addition to his formal qualifications in anatomy, Professor Henneberg is a person of extensive practical experience in examining CCTV footage, with all its deficiencies, and attempting to identify characteristics of persons depicted in it. The view he expressed on this topic is necessarily subjective and not amenable to elaboration beyond the reasons he gave, or to measurement and calculation.”
(emphasis added by me). This, correctly understood, supported the conclusion that the evidence was not based on specialised knowledge :
“Professor Henneberg's opinion was not based on his undoubted knowledge of anatomy. Professor Henneberg's knowledge as an anatomist, that the human population includes individuals who have oval shaped heads and individuals who have round shaped heads (when viewed from above), did not form the basis of his conclusion that Offender One and the appellant each have oval shaped heads. That conclusion was based on Professor Henneberg's subjective impression of what he saw when he looked at the images. This observation applies to the evidence of each of the characteristics of which Professor Henneberg gave evidence.”
The evidence was not admissible. The Court did not have to decide whether, as submitted by the appellant, to be based on specialised knowledge an opinion must be able to be independently validated .
Mere use of technical language does not mean that an opinion is based on specialised knowledge :
“Professor Henneberg's evidence gave the unwarranted appearance of science to the prosecution case that the appellant and Offender One share a number of physical characteristics. [footnote: HG v The Queen  HCA 2; (1999) 197 CLR 414 at 429  per Gleeson CJ; Morgan v The Queen  NSWCCA 257; (2011) 215 A Crim R 33 at 61  per Hidden J.] Among other things, the use of technical terms to describe those characteristics – Offender One and the appellant are both ectomorphic – was apt to suggest the existence of more telling similarity than to observe that each appeared to be skinny.”
What is the witness actually saying?
The other decision, Fitzgerald v The Queen  HCA 28 (13 August 2014) concerns a prosecution case that, it now seems, could hardly have been weaker: a trace of DNA from the defendant (appellant) was found on a didgeridoo located at the scene of a violent attack. The prosecutor, held the High Court, could not exclude innocent explanations for the DNA’s presence and the conviction was quashed and a verdict of acquittal entered.
The error in the courts below was essentially that the expert’s evidence had been misunderstood. In evaluating whether the prosecutor had proved guilt beyond reasonable doubt the High Court referred to the following points :
“On Dr Henry's evidence ... the prosecution's main contention, that the appellant's DNA in Sample 3B derived from the appellant's blood, was not made out beyond reasonable doubt. Secondly, Dr Henry's evidence was not that secondary transfer of DNA was "rare"; rather, she said that a primary transfer is a much more likely source of contact or trace DNA than a secondary transfer, but that nevertheless a secondary transfer of contact or trace DNA is possible. There was no conflict in the evidence that there were at least two distinct occasions ... on which a secondary transfer of the appellant's DNA to the didgeridoo may have occurred. Thirdly, the recovery of the appellant's DNA from the didgeridoo did not raise any inference about the time when or circumstances in which the DNA was deposited there. For those reasons, it could not be accepted that the evidence relied on by the prosecution was sufficient to establish beyond reasonable doubt that the appellant was present at, and participated in, the attack. The jury, acting reasonably, should have entertained a reasonable doubt as to the appellant's guilt. [footnote: M v The Queen (1994) 181 CLR 487 at 493-494.] Alternative hypotheses consistent with the appellant's innocence, in particular the hypothesis that Sumner [co-defendant] transferred the appellant's DNA to the didgeridoo on Sumner's first visit to the house on the day in question, were not unreasonable and the prosecution had not successfully excluded them. As the evidence was not capable of supporting the appellant's conviction for either offence, no question of an order for a new trial arose.”
Other cases on expert evidence