In R v Smith, above, Sheller JA said (at [22]), with the concurrence of the other two judges of the Court of Criminal Appeal, that an identification of a person from a photograph by another person who knows the first person well enough to recognise that person on sight involves no more inference than seeing that person and recognising him in the street. In R v Leung (1999) 47 NSWLR 405, Simpson J, in the course of dealing with the admissibility of the evidence of an ad hoc expert on voice recognition (see s 79), made the same point (at [43]), with the concurrence of the other two members of the court, when discussing the line to be drawn between opinion evidence and evidence of fact.

R v Smith was reversed in the High Court on the ground that the evidence of recognition from a photograph, given by two police officers who were not witnesses to the crime, could not rationally affect the jury’s assessment of the issue, and was therefore irrelevant, as they were in no better position than the jury to determine the issue: Smith v The Queen (2001) 206 CLR 650 at [10]–[12]. However, the majority of the court did (at [9], [11], [14]–[15]) leave open the possibility that such recognition may be relevant where there was some distinctive feature concerning the person depicted known to the police officers that would not be apparent to the jury. See, for example, R v Robinson [2007] QCA 99 at [20]. Kirby J, who dissented on the issue of relevance in Smith v The Queen, above, accepted (at [54]) the statement made by Sheller JA, but said (at [57]–[58]) that the dangers of mistakes inherent in the processes of identification and recognition make it unsurprising that evidence such as that given by the police officers has normally been classified as opinion rather than factual evidence. It has since been held, following the views of Kirby J, that, where the recognition evidence becomes relevant and thus admissible in accordance with the majority judgment, but where the photographs are of poor quality, or provide only an unusual angle or obscure part of the person in question, it is more appropriate to classify evidence of recognition as opinion evidence rather than evidence of fact: R v Drollett [2005] NSWCCA 356 at [41]–[44].

Where there has been no process of deduction rather than recognition, and no real risk of the recognition being wrong — because, for example, the familiarity the witness has with the person in question — it may still be appropriate to accept the evidence of recognition as evidence of fact rather than opinion: R v Marsh [2005] NSWCCA 331 at [18], [31]; R v Drollett, above, at [60]. See also Nguyen v R (2007) 180 A Crim R 267, discussed under s 78 (Exception: lay opinions).

In Haidari v R [2015] NSWCCA 126, Johnson J (with whom the other members of the court agreed) considered an identification issue in a trial concerning a detention centre riot. The issue was whether a client service officer at the Villawood Detention Centre had permissibly identified the appellant as a person taking part in the riot. The officer without objection purported to identify the appellant from his own observations and in an ABC film clip taken on the night. He knew the appellant from his professional dealings with him. Johnson J rejected the argument that the identification was opinion evidence. His Honour, at [76], distinguished R v Drollett, making the important point that there is no bright line between opinion and fact. He described it as “a blurred boundary”, to be determined by a close examination of the circumstances in each case. The court held that there had been no miscarriage of justice: at [78].

The admissibility of hearsay evidence of an opinion which falls within an exception to the hearsay rule is still governed by Pt 3.3 (ss 76–80) of the Evidence Act: R v Whyte [2006] NSWCCA 75 at [36], [51]. The evidence in that case was of the complainant (in a prosecution of the appellant for detaining her with intent to have sexual intercourse with her) that she had told her mother that the accused had tried to rape her. It was admissible on the issues of credit and absence of consent, and as opinion evidence pursuant to s 78 (lay opinion). It should be noted that the two judges who dealt with this issue did not agree as to the basis for its admissibility under Pt 3.3, but they were agreed that Pt 3.3 applied. The decision does not appear to have been the subject of further judicial examination.

The High Court clarified in Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588 at [37]) that the admissibility of opinion evidence is to be determined by the application of the requirements of the Evidence Act rather than by the application of statements made in decided cases divorced from the context in which those statements were made. The joint majority judgment has nevertheless adopted Heydon JA’s statement in Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705 (at [85]), that the expert’s evidence must explain how the field of “specialised knowledge” in which the witness is expert by reason of “training, study or experience”, and on which the opinion is “wholly or substantially based”, applies to the facts assumed or observed in the particular case so as to produce the opinion propounded. Note, the principles stated in Makita v Sprowles and applied in Dasreef Pty Ltd v Hawchar regarding the admissibility of expert opinion evidence under the uniform evidence legislation, apply equally to the determination of admissibility at common law: Lang v The Queen [2023] HCA 29 at [11]; [430]–[434].

No expert evidence is based exclusively on the expert's training, study, or experience. All fields of specialised knowledge assume “observations and knowledge of everyday affairs and events, and departures from them”, it being the “added ingredient of specialised knowledge to the expert’s body of general knowledge that equips the expert to give [their] opinion”: Lang v The Queen at [435]; Kiefel CJ and Gageler J at [12]; Velevski v The Queen [2002] HCA 4 at [158].

While expert opinion evidence must have a rational relationship with the facts proved (or anticipated to be proved) to be admissible, the requirement is for purported, not actual, justification for the opinion expressed: Lang v The Queen at [436].

The analysis in Dasreef accepts (at [41]) that the Evidence Act does not require the factual basis of the opinion to be established: see “Differentiation between opinion and factual basis; identification of factual basis” (below).

It is accepted that an expert need not amass all of the factual data on which the opinion is to be expressed; the task can be delegated to another, but it is necessary for the expert who is the author of the report to apply his or her mind to the analysis and reasoning that any subordinates have developed, so that, when the report is finalised, the whole of the reasoning and conclusions it contains have been adopted as the expert’s own reasoning and conclusions: ASIC v Rich (2005) 190 FLR 242 at [329]; R v Jung [2006] NSWSC 658 at [57], where Hall J gives the example of an MRI produced by a radiologist which is then utilised by a medical specialist for the purposes of forming an opinion concerning causation, diagnosis or treatment. See also Paino v Paino (2008) 40 Fam LR 96 at [66]–[67], [113].

The decision by the trial judge as to whether the opinion was wholly or substantially based on the expert’s knowledge is to be determined on the balance of probabilities (s 142), and — in accordance with the principle in Blatch v Archer (1774) 98 ER 969 at 970; Weissensteiner v The Queen (1993) 178 CLR 217 at 225–228 and Ho v Powell (2001) 51 NSWLR 572 at [14]–[15] — the evidence is to be weighed according to the proof which was in the power of one side to have produced, and in the power of the other to have contradicted: Paino v Paino at [72]–[74]. In Gilham v R (2012) 224 A Crim R 22, the trial judge had been confronted with evidence from two forensic experts opining in relation to the “similarity” of the pattern of stab wounds on the victims. The evidence was permitted and the Crown allowed to address the jury to suggest the “extraordinary co-incidence” of the similarity pointed to one perpetrator causing the death of all three victims. Applying the Dasreef test, the Court of Criminal Appeal held, at [345], that the absence of any evidence of relevant experience of fatal stab wounds inflicted by the one killer on multiple victims meant that the evidence of the experts should not have been admitted. Second, its prejudicial impact was such that it ought, in any event, to have been rejected under s 137 of the Evidence Act. In addition, the court was critical of the decision by the Crown (at the first trial) not to call an expert forensic witness the Crown had engaged whose opinion differed markedly from the other two experts. The court, at [412], stated that the Crown’s failure to call the witness at the second trial constituted a miscarriage of justice.

The “specialised knowledge” test was preferred by the Australian Law Reform Commission to the “field of expertise” test — enunciated in Frye v United States 293 F 1013 (1923), followed in R v Gilmore [1977] 2 NSWLR 935 at 939–941, and continued, despite its reversal in the United States, in R v Pantoja (1996) 88 A Crim R 554 at 558 — because of the difficulties experienced in implementing such a test and the unnecessary restrictions it imposed: ALRC Report 26, vol 1 at 743; ALRC Report 38 at 149–150.

The term “specialised knowledge” is not defined in the Evidence Act. The analogous term “expertise” adopted at common law requires a “peculiar” skill on the part of the witness (that is, one out of the ordinary experience of others); that person’s opinion becomes admissible only where the subject matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment on it without such assistance and it is of such a nature as to require a course of previous habit or study in order to do so: Clark v Ryan (1960) 103 CLR 486 at 491. An alternative formulation of the common law test is that expert opinion evidence is admissible where the information it conveys is likely to be outside the experience and knowledge of a judge or jury: Murphy v The Queen (1989) 167 CLR 94 at 111, 126, 130; Thirukkumar v Minister for Immigration and Multicultural Affairs [2002] FCAFC 268 at [18], [33]–[34]; Forbes v Selleys Pty Ltd [2004] NSWCA 149 at [56].

The phrase “specialised knowledge” in s 79 was intended to extend the common law, and to emphasise that experience can be a sounder basis for opinion than study: ALRC Report 26, vol 1, par 742. The phrase is “not restrictive; its scope is informed by the available bases of training, study and experience”: Adler v ASIC (2003) 46 ACSR 504 at [629], in which it was held that proper professional conduct, in the sense of due care and obedience to customary practices and ethical rule, was a field of specialised knowledge.

Honeysett v The Queen (2014) 253 CLR 122 is an important contribution to the learning on “opinion evidence”. It represents a necessary caution against allowing expert opinion where it is based essentially on a subjective appreciation of facts which may be equivalently assessed by the tribunal of fact.

The appellant was convicted of the armed robbery of a suburban hotel. CCTV cameras had captured images of the robbery. Professor Henneburg, an expert in anatomical matters, gave evidence of physical characteristics that were common to both the appellant and one of the robbers. Over objection, the evidence was admitted (and used by the Crown) as an item of circumstantial evidence to support a conclusion of identity.

The High Court held that the opinion expressed by the expert was based on his subjective impression of what he saw when he examined the CCTV images. However, the court said the admission of the evidence gave the “unwarranted appearance of science” to the prosecution case. His opinion was not based “wholly or substantially on his specialised knowledge” within s 79(1) and had been wrongly admitted at the trial. The court also held that, in the circumstances, Professor Henneburg’s opinion was not admissible as that of an “ad hoc” expert. A new trial was ordered.

A practical application of this necessary caution is to be found in the decision of Harrison J in Beckett v State of New South Wales [2014] NSWSC 1112.

At issue was an expert report sought to be tendered in proceedings brought by the plaintiff seeking damages for malicious prosecution. In essence, the report sought to analyse in detail the behaviour of the former detective who had been the prosecutor in the criminal proceedings giving rise to the malicious prosecution. The conduct in question involved (so it was said) intimidating witnesses; causing witnesses to give false testimony; bias and fabricating or planting physical evidence to inculcate Ms Beckett in the criminal charge of attempting to murder her husband. The expert report in question was that of a former policeman who sought to bring to bear his experience and knowledge gained over many years on the propriety of the prosecutor’s actions in assembling evidence against Ms Beckett in the criminal proceedings.

Harrison J found that (with one exception) none of the matters in the report fell within the reach of any identifiable expertise. Nor was the expert opinion on these matters otherwise relevant in the malicious prosecution proceedings. Importantly he held (echoing Honeysett) that the expert’s opinions were necessarily subjective opinions, divorced from any independent means of validation. They were not amenable to “measurement and calculation” and therefore inadmissible.

Recently, the same point was made in Verryt v Schoupp [2015] NSWCA 128. The respondent was a 12-year-old boy who had been badly injured while being “towed” on a skateboard behind a motor vehicle. The principal issue on appeal was one of contributory negligence. However, a subsidiary issue related to the admissibility of a “psychiatric report” which purported to express opinions as to how a 12-year-old boy was likely to have acted and thought in the circumstances of the accident. The psychiatrist had not made any psychiatric assessment of the respondent. Meagher JA at [59] (with whom the other members of the court agreed) held that the psychiatrist’s evidence was not based on any specialised knowledge of a 12-year-old child’s behaviour in the circumstances of the accident. For that reason, it was not admissible under s 79.

See also, Howard Smith and Patrick Travel Pty Ltd v Comcare [2014] NSWCA 215. This case dealt with the admissibility of an opinion expressed by stevedoring workers that they had been exposed to asbestos dust during their employment. The evidence was allowed as evidence by lay witnesses as to their perception. It also qualified as admissible evidence on the basis that it was specialised knowledge obtained through extensive experience.

In BHP Billiton Ltd v Dunning [2015] NSWCA 55, the Court of Appeal upheld the admissibility of the evidence of a non-expert witness that material in a steelworks factory was or contained asbestos. The witness was well familiar with the operations of the steelworks and was the person responsible for testing replacement materials for asbestos and their efficacy. The court held that the evidence was admissible as “objectively observed fact”: at [101].

In some cases, the link between the opinion expressed by the witness and his or her training, study or experience will be apparent from the nature of the specialised knowledge, such as an opinion on general conveyancing practice expressed by a solicitor with specialised knowledge of that practice, but the link would not be apparent in relation to an exotic matter of conveyancing practice, and in such a case it would have to be spelt out: Adler v ASIC, above, at [632].

The expert’s reasoning process should be sufficiently exposed to enable an evaluation as to how the expert used his or her expertise in reaching the opinion stated: HG v The Queen (1999) 197 CLR 414 at [39]–[41]; Makita (Australia) Pty Ltd v Sprowles at [85]; Keller v R [2006] NSWCCA 204 at [28]–[31]; Rylands v R (2008) 184 A Crim R 534 at [84].

In Allianz Australia Ltd v Sim [2012] NSWCA 68 the Court of Appeal held that the evidence of a distinguished pathologist, Professor Henderson, as to the causal link between exposure to asbestos dust and lung cancer was admissible. The opinions expressed emerged wholly or substantially from his expertise and knowledge so as to comply with s 79. Further, the expert was entitled to express an opinion about the ultimate causation issue: s 80.

Opinions based on the expert witness’s own interpretation of the evidence are not inadmissible, provided that the reasoning process is properly explained and is shown to depend on the expert’s specialised knowledge: ASIC v Rich (2005) 53 ACSR 110 at [289]–[291].

Where the provisions of the Evidence Act apply, the judge is permitted to take into account only those facts proved in evidence or matters of which judicial notice could be taken; matters of which the judge is otherwise aware from experience in a particular area are not relevant: Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588 at [47], overruling a long line of authority in the Full Court and the Court of Appeal starting with Bryce v Metropolitan Water Sewerage and Drainage Board (1939) 39 SR 321 at 330.

Bartlett v ANZ Banking Group Ltd (2016) 92 NSWLR 639; [2016] NSWCA 30 is a reminder that seldom, if ever, will a dispute between experts be resolved by an examination of the witnesses’ demeanour. This will be so unless the witness “has given dishonest or misleading evidence, or has become an advocate for a party, or where the evidence given is inherently unreliable”. The court described observations of an expert’s demeanour as “a last resort”. The differences between experts should usually be resolved by rational analysis.

The words “training, study or experience” necessarily include observations and knowledge of everyday affairs and events and of departures from them, and it will frequently be impossible to divorce entirely those observations and that knowledge from the body of purely specialised knowledge on which an expert’s opinion depends; it is the added ingredient of specialised knowledge to the expert’s body of general knowledge that equips the expert to give his or her opinion: Velevski v The Queen (2002) 76 ALJR 402 at [158]. Reference was also made at [158] to s 80, see [4-0640].

In an appeal from a ruling rejecting expert evidence tendered as to what led members of the public to decide to purchase a particular brand of chocolate because that was quintessentially a question of fact within the experience and knowledge of the tribunal of fact, the Full Federal Court has held that, because of s 80 (Ultimate issue rule abolished), expert evidence remains admissible notwithstanding that the issue to be determined remained within the experience and knowledge of the tribunal of fact: Cadbury Schweppes Pty Ltd v Darrell Lea Chocolate Shops Pty Ltd, above, at [51]–[57]. Special leave to appeal was refused by the High Court, but it appears to have been sought only in relation to the order made by the Full Court that the matter be returned to the original trial judge for further hearing, rather than a new trial before a different judge: Cadbury Schweppes Pty Ltd v Darrell Lea Chocolate Shops Pty Ltd [2007] HCA Trans 468. See also Chen v R [2018] NSWCCA 106 where these matters are reinforced.

In consumer decision-making and similar cases, knowledge of actual mistake or confusion arising where there has been a particularly close similarity in brand names does not amount to specialised knowledge of the factors that may be causative of, and conditions that create the likelihood of, mistake or confusion in the decision-making purchasers that satisfies the test in Clark v Ryan, above: CA Henschke and Co v Rosemount Estates Pty Ltd (1999) 47 IPR 63 at [75]–[76]; these rulings were upheld on appeal: CA Henschke and Co v Rosemount Estates Pty Ltd (2000) 52 IPR 42 at [17]–[18].

A person experienced in training programmes for the long-term unemployed is qualified to express an opinion as to the capacity of such a person to carry out particular types of work becoming available through the Commonwealth Employment Service: Hospitality Excellence Pty Ltd v State of NSW [1999] NSWSC 945 at [10]; but such a person is not, without more, qualified to express opinions as to the probability of that person being employed in that work or the financial benefits from such employment: at [11]–[14].

In Hawkesbury Sports Council v Martin [2019] NSWCA 76, the primary judge erred in admitting expert opinion evidence for the respondent as to matters of visual perception and vision science: at [33]. The expert's report did not explain how his opinions, based on “specialised knowledge”, in turn based on his “training, study or experience” and on which the opinion is “wholly or substantially based”, applied to the facts assumed or observed so as to produce the opinion propounded as required by s 79: at [33]; Makita (Australia) Pty Ltd v Sprowles at [85].

Failure to demonstrate that an opinion is based on a witness’s specialised knowledge, based on his or her training, study or experience goes to the admissibility of the evidence, not its weight: Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588 at [42]; Nicholls v Michael Wilson & Partners Ltd [2012] NSWCA 383 at [209].

Both the Supreme Court Act and Rules and the District Court Act adopt the expert witness code of conduct provided in Sch  7 to the Uniform Civil Procedure Rules 2005. In Chen v R (2018) 97 NSWLR 915, an interpreter whose written statement had been served, and who was later called to give oral evidence, had not made the acknowledgement required by Pt 75 of the UCPR. The trial judge ruled that the witnesses’ failure to be aware of the expert code did not create an absolute bar to admissibility. He suggested that the issue could be dealt with by appropriate directions to the jury. The court agreed with the trial judge’s decision, holding that failure to comply did not result in the mandatory exclusion of the interpreter’s evidence. However, in an appropriate case, the failure may be relevant to a consideration of the issues in ss 135 and 137 of the Evidence Act. See also Wood v R (2012) 84 NSWLR 581.

The Court of Criminal Appeal, in Wood v R, ordered the acquittal of the accused, Gordon Wood. A significant basis of the court’s decision related to its unfavourable view of the principal expert relied on by the Crown to exclude the possibility of the deceased’s suicide. The decision contains the useful statement of the obligations cast upon an expert both by the general law and the expert witness code of conduct: [719]–[729].

Note in Alora Davies Developments 104 Pty Ltd (in liq) [2024] NSWSC 335, a liquidator giving evidence in the liquidator’s own case was held to be an “expert” but not an “expert witness” for the purposes of the definitions in UCPR r 31.18. As a result, UCPR r 31.23 did not apply. It was not necessary to dispense with the requirements of the expert witness code in this case although Black J would likely have done so, had he been asked to do so and had it been necessary to do so: at [7].

An expert whose opinion is tendered should differentiate between the assumed facts on which the opinion is based and the opinion in question, to enable the court to identify the facts the witness has either observed or accepted and to distinguish between them and the witness’s expressions of opinion; s 79 requires that the opinion be presented in a form which makes it possible to determine whether the opinion is wholly or substantially based on specialised knowledge based on training, study or experience, and such form requires or invites a demonstration or examination of the scientific basis of the conclusion: HG v The Queen (1999) 197 CLR 414 at [39], [41]; TCN Channel Nine Pty Ltd v Anning (2002) 54 NSWLR 333 at [144]; ASIC v Rich at [98]–[101], [109]; R v Tang (2006) 65 NSWLR 681 at [147]–[153]; Hamod v Suncorp Metway Insurance Ltd [2006] NSWCA 243 at [37]; Hancock v East Coast Timber Products Pty Ltd (2011) 80 NSWLR 43 at [69].

If those matters are not made explicit in chief, it would normally not be possible for the court to make a judgment as to whether the prerequisites of s 79 have been satisfied and whether the evidence is admissible, and in any event the opinion will be valueless without proof of such factual basis: Cadbury Schweppes Pty Ltd v Darrell Lea Chocolate Shops Pty Ltd (2007) 239 ALR 662 at [107]–[108]; Hancock at [73]–[78]. The prime duty of an expert is to identify the facts and reasoning process which justify the opinion expressed. That is sufficient to enable the tribunal of fact to evaluate the opinion expressed: ASIC v Rich (2005) 218 ALR 764 at [105]. If, however, the material on which the expert opinion is based is not supported by admissible evidence, the opinion may have little or no value, for part of the basis of the opinion is gone: Hancock at [76], citing Ramsay v Watson (1961) 108 CLR 642 at 649.

Experts who venture opinions outside their field of specialised knowledge, which are sometimes no more than their own inferences of fact, may invest those opinions with a spurious appearance of authority, and legitimate processes of fact-finding may be subverted: HG v The Queen, above, at [44]. In that case, the Chief Justice criticised the psychologist’s opinion tendered in that case has having been based on “a combination of speculation, inference, personal and second-hand views as to the credibility of the complainant, and a process of reasoning which went well beyond the field of expertise of a psychologist”, and held that it had not been shown to have been based, either wholly or substantially, on the proposed witness’s specialised knowledge as a psychologist. By directing attention to whether an opinion is wholly or substantially based on specialised knowledge in which the witness is expert by reason of training, study or experience, s 79 will not be satisfied unless the opinion is presented in the form that makes it possible to answer that question: HG v The Queen at [39].

Sackville AJA repeated this point in Nicholls v Michael Wilson & Partners Ltd [2012] NSWCA 383 at [242] and [243]. It was also reinforced in criminal proceedings in Kyluk Pty Ltd v Chief Executive, Office of Environment and Heritage (2013) 298 ALR 532. Indeed, the latter decision at [63]–[69] and [176]–[179] suggests that in a criminal trial, where important facts supporting an expert opinion have not been proved, s 135 will require the discretionary rejection of the evidence, even where the opinion is arguably admissible.

Where an opinion becomes admissible pursuant to s 79, the absence of explanations, discussion and analysis may reduce its probative value to such an extent that that value would be outweighed by its probative effect: Paino v Paino [2005] NSWSC 1336 (Barrett J) at [27]. (This proposition was not disputed in the subsequent successful appeal: Paino v Paino (2008) 40 Fam LR 96).

The expert evidence of a witness must identify what the witness asserts was an adequate basis for his opinion; matters concerning the process by which an opinion was actually formed go the weight, and not the admissibility, of the evidence, and are relevant to the exercise of the discretion given by s 135: ASIC v Rich at [94]. If the proposed evidence identifies the facts asserted to be the basis of the opinion and the process of reasoning by which the opinion was formed, and if the opinion is capable of being based on those facts, the evidence is admissible: at [135]–[136]. The facts do not need to have been proved at the stage the opinion is tendered: at [136]. The issue then for the tribunal of fact is whether the opinion expressed on the facts proved or assumed is correct; in determining this issue, regard must be had, among other things, to the reasoning process (based on those facts) used by the expert: at [136].

The law remains that there is no requirement in the Evidence Act for the admissibility of opinion evidence that the factual basis of the opinion to be established either before that evidence may be given or at all, although the absence of such factual evidence at the time the opinion is tendered may, subject to s 136, lead to it being admitted conditionally, and its absence at the end of a particular case may lower the weight of any opinion based on the assumption that the factual basis exists to the point where its use may be limited pursuant to s 136. On the other hand, a failure to establish that the opinion expressed by an expert is based on the expert’s specialised knowledge based on training, study or experience goes to its admissibility, not its weight: Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588 at [41]–[42]; applied in Hawkesbury Sports Council v Martin [2019] NSWCA 76 at [28].

In Sharma v Insurance Australia Limited t/as NRMA Insurance [2017] NSWCA 55, the appellant had lost his case at first instance because the trial judge did not accept that the appellant had injured his wrists in a fall from a ladder. Part of the evidence tendered at trial consisted of a number of medical certificates prepared for the purpose of explaining to an employer that the appellant would be unable to attend to his usual employment. These recorded the appellant’s claim to the relevant doctors that he had injured his wrists in a fall. The trial judge found that these certificates assumed the correctness of the medical history provided by the appellant but contained no reasoning process to validate any opinion expressed. Applying Makita (Australia) Pty Ltd v Sprowles, above, and Dasreef Pty Ltd v Hawchar, above, the Court of Appeal held that the medical certificates were not admissible. They did not explain the experts’ fields of “specialised knowledge”, nor the facts on which any opinion was based. In each case, the document was “a medical certificate intended for use in an employment rather than a curial context”. For that and other reasons, the appeal was dismissed.

Evidence given by police officers in relation to covertly recorded conversations between person alleged to have been involved in drug transactions — in which the evidence seeks to translate the codes used by the participants in those conversations as referring to the particular drugs and quantities being bargained — requires close attention to the requirements of s 79 and the application of s 135, in that the witnesses who give such evidence frequently base their opinions on information concerning the participants which is not part of their specialised knowledge, such as information concerning the activities of the participants conveyed by other police officers who had participated in the police investigation. This material must be identified and proved before the opinions become admissible. In many cases, the other activities revealed disclose uncharged conduct and raise tendency problems. The relevant authorities are reviewed in Nguyen v R (2007) 173 A Crim R 557 at [36]–[58].

A good example of the issues that may arise is found in Beech-Jones J’s decision in JP v DPP (NSW) [2015] NSWSC 1669. A police fingerprint expert provided a certificate which gave brief details of his methodology and then certified that, in his opinion, the defendant’s fingerprint was identical to a fingerprint found at a break-and-enter crime scene. However, he was cross-examined over several days and during the cross-examination, gave much more detail of his methodology. Justice Beech-Jones accepted that the brief statements in the report of the fingerprint evidence would not have satisfied the requirement that the claimed field of expertise must be shown to have adhered to the facts found (or assumed) to produce the opinion expressed. In the case of expert fingerprint evidence there must be at least some detail of the points of similarity and how those points have been ascertained and identified. It will often be the case with this type of expert evidence that “little explicit articulation or amplification” will be required: at [33]. However, Beech-Jones J held in dismissing the appeal that the expert’s oral evidence “filled the gaps” and secured admissibility for the expert opinion.

Nguyen v R at [60]–[65] demonstrates the importance of the identification of the specialised knowledge on which such an opinion was based. That decision and a number of earlier cases — Keller v R [2006] NSWCCA 204 at [24]–[31] and Chow v R (2007) 172 A Crim R 582 at [50]–[55] — insist that, in the absence of an identification of the contextual matters which led to the opinion that they were references to drugs, an expert in these cases must be restricted to saying that the code words are consistent with references to drugs.

At the stage when the admissibility of an expert opinion is being considered, and where the factual basis of the opinion is established by hearsay evidence, the opinion is admissible, and the hearsay evidence — having been admitted for the purpose of the admissibility of the opinion — becomes evidence of the truth of the hearsay facts stated in accordance with s 60: Bodney v Bennell (2008) 249 ALR 300 at [92]–[93].

Section 79 is sufficiently wide to accommodate the idea of an ad hoc expert witness: R v Leung (1999) 47 NSWLR 405 at [36]–[40]. Examples given are of a tape-recording that was substantially unintelligible to anyone who had not played it repeatedly but is then played repeatedly by a person until that person is able to decipher it, and of a tape recording in a foreign language that can be deciphered only by a person familiar with the language who plays it repeatedly: R v Menzies [1982] 1 NZLR 40 at 49; Butera v DPP (Vic) (1987) 164 CLR 180 at 187–188; Eastman v R (1997) 158 ALR 107 at 201–203; R v Cassar [1999] NSWSC 436 at [6]–[7]. Nguyen v R [2017] NSWCCA 4 is another example of a police officer listening to intercepted calls over a lengthy period of time. The officer’s repeated listening gave his identification evidence the quality of ad hoc expertise, and thus was admissible as expert evidence.

The Victorian Supreme Court of Appeal accepted that a police detective had the training and experience, falling short of formal qualifications, placing him in a position of having knowledge as to the effects on concrete of burning accelerants beyond that of a person lacking that training and experience: Davies v R [2019] VSCA 66 at [177].

In Morgan v R [2016] NSWCCA 25, the appellant had been convicted of a series of “break and enter” offences by circumstantial evidence and voice identification evidence. A tracking device containing a listening device had been placed in a stolen BMW allegedly used by the appellant and his co-defendants. After a voir dire, the trial judge allowed into evidence the “ad hoc” expert evidence of a police officer in relation to voice similarity. The officer had extensively compared the voices on the listening devices with conversations recorded between the appellant and his partner while he was in custody. The CCA held that Honeysett v The Queen (2014) 253 CLR 122 did not cast doubt on the use of “ad hoc” experts. At best, the issue remained to be decided. In any event, the precise point had not been taken at trial and leave to do so was refused in the appeal.

Where an issue arises as to the state of specialised knowledge of some particular issue at some time in the past, an expert in that particular field (even though not an expert at that time) is permitted to give evidence, based on the literature of that particular time, as to what that state of knowledge was at that time: BI (Contracting) Pty Ltd v University of Adelaide [2008] NSWCA 210 at [20]–[26].