[SUPREME COURT of SOUTH AUSTRALIA] the QUEEN V BONYTHON KING CJ, MATHESON and BOLLEN JJ 21 November 1984; 19 December 1984

[SUPREME COURT OF SOUTH AUSTRALIA] THE QUEEN V BONYTHON KING CJ, MATHESON and BOLLEN JJ 21 November 1984; 19 December 1984 Criminal Appeal. The facts are stated in the judgment of King C.J. K. V. Borick and B. W. McQuade, for the appellant. P. J. Rice, for the Attorney-General. Cur. adv. vult. KING CJ: The appellant appeals against his conviction by a jury in the Supreme Court of the crimes of forging and uttering a request for the payment of money. The case for the prosecution was that the appellant forged the signature of a Miss Bell on the request. The grounds of the appeal which were argued before us are that the opinions of a police sergeant Daly that the signatures were not those of Miss Bell were wrongly admitted into evidence and that the trial Judge erred in not allowing the examination of the witness on the voir dire to take place in the absence of the jury. At the commencement of the trial, counsel for the appellant, in the absence of the jury, asked to be permitted to examine Sergeant Daly on the voir dire in the absence of the jury. The learned trial Judge refused the request. When Sergeant Daly was called in the presence of the jury, he was examined by counsel for the prosecution as to his qualifications to express opinions as to handwriting and the identification of signatures. He gave evidence of a five year period of training under a police handwriting expert, of his reading of recognized works on the subject, of his discussions with experts from other jurisdictions, and of an extensive experience in handwriting comparison and of giving evidence on the subject. He was cross-examined on the voir dire in the presence of the jury. After questioning the witness about his knowledge and experience of the subject, counsel began to cross-examine the witness as to the number of standard signatures which would be required to enable the witness to express an opinion as to whether a particular signature was made by the person who made the standard signatures. At that point the Judge ruled that that question related to the weight of the evidence and not to its admissibility. In the course of discussion with counsel, the learned Judge indicated his view that questions designed to establish that the materials upon which the witness formed his opinion were inadequate, related to weight and not to admissibility. The general rule is that a witness may give evidence only as to matters observed by him. His opinions are not admissible. One of the recognized exceptions to this rule is that which relates to the opinions of an expert. This exception is confined to subjects which are not, or are not wholly, within the knowledge and experience of ordinary persons; Clark v. Ryan1 . On such subjects a witness may be allowed to express opinions if the witness is shown to possess sufficient knowledge or experience in relation to the subject upon which the opinion is sought to render his opinion of assistance to the court. Before allowing a witness to express such opinions, the judge must be satisfied that the witness possesses the necessary qualifications, whether those qualifications be acquired by study or experience or both. But when it is established that the witness is an expert in the relevant field of knowledge, he will be permitted to express his opinion, however unconvincing it might appear to be (Commissioner for Government Transport v. Adamcik2 ), subject always, of course, in a criminal trial to the discretion to exclude evidence whose prejudicial effect is disproportionate to its probative value. The weight to be attached to his opinion is a question for the jury. The principal argument advanced by Mr. Borick for the appellant was that counsel at the trial should have been permitted on the voir dire to investigate by cross-examination the question of the adequacy of the material upon which the witness based his opinion. He argued that that line of cross-examination amounted to an investigation of the method by which the opinion was reached and that the Judge was required to be satisfied as to the soundness of the methodology adopted before allowing the evidence to be given. Before admitting the opinion of a witness into evidence as expert testimony, the judge must consider and decide two questions. The first is whether the subject matter of the opinion falls within the class of subjects upon which expert testimony is permissible. This first question may be divided into two parts: (a) whether the subject matter of the opinion is such that a person without instruction or experience in the area of knowledge or human experience would be able to form a sound judgment on the matter without the assistance of witnesses possessing special knowledge or experience in the area, and (b) whether the subject matter of the opinion forms part of a body of knowledge or experience which is sufficiently organized or recognized to be accepted as a reliable body of knowledge or experience, a special acquaintance with which by the witness would render his opinion of assistance to the court. The second question is whether the witness has acquired by study or experience sufficient knowledge of the subject to render his opinion of value in resolving the issues before the court. An investigation of the methods used by the witness in arriving at his opinion may be pertinent, in certain circumstances, to the answers to both the above questions. If the witness has made use of new or unfamiliar techniques or technology, the court may require to be satisfied that such techniques or technology have a sufficient scientific basis to render results arrived at by that means part of a field of knowledge which is a proper subject of expert evidence. Examples of cases in which that question arose are The Queen v. Gilmore3 , The Queen v. McHardie and Danielson4 and United States v. Williams5 . An investigation of the methods adopted by a witness may be relevant to an assessment of his qualifications as a witness if such an investigation might reveal that the witness has "posing as an expert made assertions that are contrary to proved scientific facts or to the known phenomena of nature, thus exposing his ignorance of the learning he professed" (Commissioner for Government Transport v. Adamcik6 , per Windeyer J. at p. 306), or that the witness has adopted methods which are so unscientific as to expose that ignorance. Where the witness possesses the relevant formal qualifications to express an opinion on the subject, an investigation on the voir dire of his methods will rarely be permissible on the issue of his qualifications. There may be greater scope for such examination where the alleged qualifications depend upon experience or informal studies. The trial judge must have a wide discretion as to what may be investigated on the voir dire and the scope for interference by an appellate court with the way in which the discretion is exercised must be limited. Generally speaking, once the qualifications are established, the methodology will be relevant to the weight of the evidence and not to the competence of the witness to express an opinion. The suitability and adequacy of the methods used may well be themselves a matter of expert opinion. Certain submissions made by counsel seemed to imply some uncertainty as to the reach of the decision of the Full Court in The Queen v. Duke7 . In that case the trial Judge was asked to exercise his discretion to exclude admissible evidence as to the presence of certain blue fibres on the back seat of the accused's car and expert evidence identifying those fibres as coming from the alleged victim's dress on the ground that the prejudicial effect of the evidence was disproportionate to its probative value. The Court held that in deciding whether to exercise his discretion to exclude the evidence, the weight of the evidence is to be assessed by the judge upon a consideration of the evidence which the prosecution proposes to present and that it is not the function of the judge in deciding that question to hear conflicting expert evidence in order to determine for himself the disputed scientific issues. Where, however, the admissibility of any piece of evidence depends upon the existence of a fact or state of facts, the judge must determine the existence of the fact or state of facts in order to rule on the admissibility of the evidence. For that purpose it may be necessary to hear conflicting evidence on the voir dire in order to determine any dispute as to those facts. If the qualifications of a witness to give expert evidence are in issue, it may be necessary to hear evidence on the voir dire in order to make a finding as to those qualifications. If there is an issue as to whether the subject matter upon which the opinion is sought is a proper subject of expert evidence, any disputed facts relevant to the determination of that issue should be resolved by the reception of evidence on the voir dire. The Queen v. Duke8 was not concerned with any such issues. There could be no question in the present case as to whether the subject matter was proper for expert testimony. Comparison of handwriting and identification of signatures is a well-established field for expert testimony. Although there is no course of formal study in the subject, the qualifications of the witness acquired by informal study, practical instruction and experience are considerable.

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