Murphy (a pseudonym) v The King - [2023] SASCA 107

SUPREME COURT OF SOUTH AUSTRALIA
(Court of Appeal: Criminal)
MURPHY (A PSEUDONYM) v THE KING
[2023] SASCA 107
Judgment of the Court of Appeal
(The Honourable President Livesey, the Honourable Justice Lovell and the Honourable Auxiliary Justice Buss)
29 September 2023
CRIMINAL LAW - GENERAL MATTERS - CRIMINAL LIABILITY AND CAPACITY - DEFENCE MATTERS - INSANITY AND MENTAL IMPAIRMENT - EVIDENCE - MEDICAL AND PSYCHIATRIC EVIDENCE
The appellant is charged with various offences of sexual wrongdoing against under-age males. Relying on s 269C(1) of the Criminal Law Consolidation Act 1935 (SA) (CLCA) the appellant put his mental competence into issue.
The trial of the issue of mental competence was heard by the judge alone. The prosecution tendered evidence including affidavits from the complainants. The appellant tendered expert reports from two psychologists, one of whom was appointed by the court.
Neither party objected to the evidence tendered by the other party, nor explained the basis on which it was received. Neither party required that the other party call its witnesses, apart from the two experts, who were cross-examined by the prosecution.
The experts had concluded that the appellant was mentally incompetent by reason of mental impairment, being Autism Spectrum Disorder, a mental illness recognised by DSM 5.
The cross-examinations of the experts challenged the assumptions they had made and the reasoning they had employed. No objection was made to the cross-examinations.
There were no oral final addresses. The trial judge reserved and received written final addresses.
The trial judge rejected the expert opinion evidence and found that the appellant had not established that he was mentally incompetent by reason of mental impairment.
The appellant appealed, seeking a finding from the Court of Appeal under s 269Y that he was not mentally competent within s 269C(1) of the CLCA.
At the hearing of the appeal, the Court granted permission to appeal, allowed the appeal and ordered a re-trial. These are the reasons for the making of those orders.
HELD (the Court):
1.Though not embraced within the grounds of appeal, the mental competence hearing miscarried because the wrong legal test was applied, the parties were in disagreement about the evidence that was properly before the trial judge and on which the experts were asked to express their opinions, and the precise basis on which the trial judge rejected the expert opinions remained unclear.
2.In circumstances where the wrong legal test was applied, and there remains a dispute about the evidence before the court, this is not a case where the Court of Appeal can review the record and form its own views.
3.Observations made about proper practice when leading expert opinion evidence, and proving the factual basis for expert opinion evidence, in an investigation into mental competence under Part 8A of the CLCA.
4.Aspects of the grounds of appeal addressed, including the concept of “wrongfulness”, procedural fairness and compliance by the parties and the court with the rule in Browne v Dunn in connection with an investigation into mental competence.

Criminal Law Consolidation Act 1935 (SA) s 269C, 269F, 269Y; Criminal Procedure Act 1921 (SA) s 158; Magistrates Court Act 1991 (SA) s 42(5), referred to.
Allied Pastoral Holdings Pty Ltd v Federal Commissioner of Taxation [1983] 1 NSWLR 1; Arnott's Ltd v Trade Practices Commission (1990) 97 ALR 555; Assistant Commissioner Condon v Pompano Pty Ltd (2013) 252 CLR 38; Bale v Mills (2011) 81 NSWLR 498; Boothy v Morris [2002] SASC 126; Browne v Dunn (1893) 6 R 67 HL; Bulstrode v Trimble [1970] VR 840; Burke v Corruption and Crime Commission (2012) 289 ALR 150; Chanaa v Zarour [2011] NSWCA 199; Clark v Ryan (1960) 103 CLR 486; Commonwealth v Muratore (1978) 141 CLR 296; Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588; Douglass v The Queen (2012) 86 ALJR 1086; F Hoffmann-La Roche & Co AG v Secretary of State for Trade and Industry [1975] AC 295; Fingleton v The Queen (2005) 227 CLR 166; Fox v Percy (2003) 214 CLR 118; Hone v Western Australia (2007) 179 A Crim 138; KBT v The Queen (1997) 191 CLR 417; Kioa v West (1985) 159 CLR 550; Kosian v The Queen (2013) 40 VR 335; Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361; Lacey v Attorney-General of Queensland (2011) 242 CLR 573; Macks v Viscariello (2017) 130 SASR 1; Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705; Merrey v The State of Western Australia [2010] WASCA 62; Mizzi v The Queen (1960) 105 CLR 659; Nadebaum v Police [2020] SASC 23; NBM v The Queen [2021] SASCA 105; New South Wales v Canellis (1994) 181 CLR 309; Orreal v The Queen (2021) 274 CLR 630; Paric v John Holland (Constructions) Pty Ltd (1985) 62 ALR 85; Pemble v The Queen (1971) 124 CLR 107; Perera-Cathcart v The Queen (2017) 260 CLR 595; Police v Mahon [2022] SASCA 76; Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135; R v Baden-Clay (2016) 258 CLR 308; R v BGC [2022] SADC 54; R v Birks (1990) 19 NSWLR 677; R v Bjordal (2005) 93 SASR 237; R v Bonython (1984) 38 SASR 45; R v Cawte [2018] SASC 182; R v Chaulk [1990] 3 SCR 1303; R v Draoui (2015) 122 SASR 360; R v Hall (1988) 36 A Crim R 368; R v Keyte (2000) 78 SASR 68; R v Lado [2020] SASC 223; R v Leach [2002] SASC 321; R v M (1977) 16 SASR 589; R v Michaux [1984] 2 Qd R 159; R v NCT (2009) 26 VR 247; R v Pesamino [2020] NSWSC 1188; R v Porter (1933) 55 CLR 182; R v Rasmussen [2018] SASC 164; R v Sexton [2018] SASCFC 28; R v Stevens (2010) 107 SASR 456; R v Taylor [2014] SASCFC 112; Ramsay v Watson (1961) 108 CLR 642; Re Minister for Immigration and Multicultural Affairs and Another; Ex Parte Miah (2001) 206 CLR 57; Re Refugee Review Tribunal; Ex parte Aala (2000) 204 CLR 82; Reid v Kerr (1974) 9 SASR 367; RP v The Queen (2016) 259 CLR 641; Rye v Western Australia (2021) 288 A Crim R 174; S, N v Police [2021] SASC 49; Scuteri v Wood (1987) 137 LSJS 7; Stead v State Government Insurance Commission (1986) 161 CLR 141; Taylor v The Queen (1978) 45 FLR 343; The Queen v Vallance [1964] SASR 361; Trade Practices Commission v Arnott's Ltd (No 5) (1990) 92 ALR 527; Village Cay Marina Ltd v Acland [1998] BCC 417; Western Australia v Djurasovic [2021] WASC 466; Williams v Dawson (2000) 31 MVR 559, considered.

MURPHY (A PSEUDONYM) v THE KING
[2023] SASCA 107
Court of Appeal – Criminal: Livesey P, Lovell JA and Buss AJA
THE COURT:
Introduction

The appellant has been charged with three counts of maintaining an unlawful sexual relationship with a child, contrary to s 50 of the Criminal Law Consolidation Act 1935 (SA) (CLCA). It is alleged that the offending occurred between January 2014 and November 2017, when the appellant was aged between 20 and 23 years, and the three males were aged between nine and 16 years.
The appellant raised the “defence” of mental incompetence pursuant to s 269C(1)(b) of the CLCA. That defence was supported by the opinions of Professor Robyn Young and Ms Susan Heinrich, psychologists. They had examined the appellant and diagnosed, or accepted the diagnosis of, Autism Spectrum Disorder (ASD). Both psychologists expressed the opinion that the appellant was not mentally competent because he did not know that his conduct was wrong within the meaning of s 269C(1)(b) of the CLCA.
A trial on the issue of mental competence was conducted pursuant to s 269F of the CLCA on 3 February 2022. In reasons provided on 5 May 2022, the trial judge rejected the opinions of the psychologists and held that he was not satisfied on the balance of probabilities that the appellant did not know that his conduct was wrong.
As will be seen, there were a number of difficulties with the conduct of the mental competence investigation before the trial judge. The wrong legal test was applied, the parties were in disagreement about the evidence that was properly before the trial judge and on which the experts were asked to express their opinions, and the precise basis upon which the trial judge proceeded to disagree with and reject the opinions of the experts remained unclear.
As a result, the mental competence investigation miscarried. At the conclusion to the hearing of this appeal on 8 September 2022, the Court made the following orders pursuant to s 269Y(3) of the CLCA:
1.The appellant is granted permission to appeal.
2.The appeal is allowed.
3.The orders made by the trial judge on 5 May 2022 are set aside.
4.The matter is remitted for retrial before a different judge in the District Court.
Our reasons for making these orders are set out as follows:
Introduction
The circumstances of the alleged offending
The trial concerning mental competence
Section 269Y and the grounds of appeal
Two preliminary matters - miscarriage
The wrong legal test was applied
The parties were in dispute about the evidence before the court
The tender of the prosecution evidence in this case
The tender of the expert opinion evidence in this case
The trial judge’s reasons regarding the expert opinion evidence in this case
An investigation into mental competence under Part 8A
Expert opinion evidence in a mental competence investigation
Appeal ground 1 – the concept of wrongfulness
Appeal ground 2 – the trial judge’s finding cannot be supported
Appeal ground 3 – there was a denial of procedural fairness
Appeal ground 4 – the trial judge’s reasons were inadequate
Conclusion
The circumstances of the alleged offending
The charges of maintaining an unlawful sexual relationship with a child concern three complainants, who are cousins, TF (count one), SW (count two) and NW (count nine). The two younger complainants, SW and NW, are brothers. As to these complainants, there are alternative charges referable to particular, identifiable incidents. The appellant is charged with 13 counts of sexual wrongdoing overall.
The circumstances of the appellant’s alleged offending were set out in a bundle of affidavits produced by the respondent at the hearing.
The offending is alleged to have occurred when the appellant was aged between 20 and 23 years, when TF was aged between 13 and 16 years, and SW and NW were aged between nine and 12 years.
The appellant came to know the three complainants through connections made between their families and a church community to which they all belonged.
In broad terms, the offending occurred in a context where the appellant spent a great deal of time with the complainants. In the case of TF, the appellant bought him presents and took him to cricket matches in a motor vehicle he owned. The complainants described instances of the appellant “talking dirty” to them, asking them if they wished to touch him and saying that he wanted to touch them. There were numerous instances of touching the boys in the area of the groin on both the outside and inside of their clothing. This developed into mutual masturbation. The offending typically involved the appellant stimulating the penis of a complainant.
In the case of TF this occurred on numerous occasions in the appellant’s car as well as in the appellant’s home, particularly during sleepovers. The appellant later lived in the home of TF for around nine months and slept in the same bedroom where the offending continued. Soon after TF turned 16 years, he told the appellant to stop and, eventually, there was a physical altercation. When the altercation came to the attention of TF’s parents the appellant was moved out of TF’s bedroom. According to TF, the appellant continued to come back into his bedroom and on one occasion TF punched the appellant in the stomach. On other occasions the appellant left when told to do so.
TF described seeing the appellant stimulate SW’s penis and touch NW on the penis, including during camping trips involving their respective families. The complainants described the appellant instigating the masturbatory conduct, commencing with ‘dirty comments’ or touching one of the complainants on the groin. On occasion, there were camping trips involving only the appellant, SW and NW and their families. The offending continued on those trips as well.
According to NW there was an occasion when SW pulled NW away from the appellant and told him to stop because the behaviour was rude. The allegation is that the appellant was told that what he was doing was wrong.
Ultimately in October or November 2017 TF told his parents about the appellant’s conduct. At that time the appellant was still living in TF’s home and working for TF’s father. TF’s father spoke with the appellant, effectively telling him that what he had been doing was wrong. Eventually in February 2019 TF’s mother reported the matter to police.
When interviewed by police, the appellant said that he had informed his mother about his issues and that it was all his fault and all in his head. The appellant said that he was hoping that he would be detected so that he could be helped. He described his conduct as a way of connecting with others and what he did is “what guys do”. He told police that TF had taken the appellant under his wing but admitted that he knew TF was too young.
The appellant also told police that SW and NW were “always very much into that sort of thing” and that SW was very knowledgeable about sexual orientation. The appellant denied instigating sexual misconduct with the complainants, describing it as a “mutual decision between them”.[1]
[1] R v BGC [2022] SADC 54, [37]-[38].
The trial concerning mental competence
Pursuant to s 269E(1)(a) of the CLCA, the appellant put into issue his mental competence.
The parties jointly requested that the trial judge first proceed with a hearing concerning mental competence pursuant to s 269FA of the CLCA.
That trial proceeded on 3 February 2022. There has, as yet, been no trial of the objective elements of the alleged offending under s 269FB of the CLCA.
At the trial, the prosecution tendered what was described as a “truncated brief” containing affidavits from the complainants, and affidavits from the father of one of the complainants and from the investigating officer to which a transcript of the appellant’s record of interview was exhibited. Counsel for the appellant took no objection to the tender of this material.
Counsel for the appellant tendered a book of the reports and other documents received from the two psychologists, Professor Young and Ms Heinrich. Again, there was no objection to the tender of this material. Those experts were called by the appellant to give evidence. The prosecution cross-examined them.
The trial judge then adjourned to enable the parties to prepare detailed written closing submissions. The trial judge did not receive the benefit of oral closing addresses before delivering his ruling.
Section 269Y and the grounds of appeal
The appellant’s appeal is brought pursuant to s 269Y(3) of the CLCA. Insofar as is relevant, s 269Y provides:
269Y—Appeals
…
(3)An appeal lies with the permission of the court of trial or the appropriate appellate court against a key decision by the court of trial.
(4)     A key decision is—
(a)     a decision that the defendant was, or was not, mentally competent to commit the offence charged against the defendant; or
(b)     a decision that the defendant is, or is not, mentally unfit to stand trial; or
(c)     a decision that the objective elements of an offence are established against the defendant.
(5)On an appeal, the appellate court may exercise one or more of the following powers:
(a)     confirm, set aside, vary or reverse a decision of the court of trial;
(b)     direct a retrial of the case or an issue arising in the case;
(c)     make any finding or exercise any power that could have been made or exercised by the court of trial;
(d)     make ancillary orders and directions.
It may be seen that both a defendant and the prosecution may, with the permission of the trial court or the appeal court, appeal against a “key decision” made by the court of trial. By s 269Y(4)(a), a “key decision” is defined to include a decision about whether the defendant was mentally competent to commit the offence charged.
It has been held that an appeal under s 269Y is by way of rehearing, and the powers of the Court are to be equated to those available under s 42(5) of the Magistrates Court Act 1991 (SA) because the express powers conferred by s 42(5) resemble the express powers conferred by s 269Y(5) of the CLCA.[2]
[2] R v Stevens (2010) 107 SASR 456, [19]-[20] (Sulan J, with whom Nyland and Layton JJ agreed); R v Taylor [2014] SASCFC 112, [16]-[18] (Stanley J, with whom Kelly and Peek JJ agreed); R v Draoui (2015) 122 SASR 360, [87] (Blue J, with whom Kelly and Bampton JJ agreed). As for the approach to appeals under s 42(5), see S, N v Police [2021] SASC 49, [2] (Lovell J); Police v Mahon [2022] SASCA 76, [81]-[84] (Livesey P, Lovell and Doyle JJA).
This Court is therefore required to conduct a “real review” of the record, together with any further materials which it may admit, so as to determine whether the trial judge made any material error of fact or law. The Court will not disregard the judgment of the primary judge, but carefully take it into account, together with any advantage the primary judge may have had from seeing and hearing the witnesses and the evidence unfold. If the Court decides that there was material error, it must substitute any order that it considers should be made unless the respondent demonstrates that, despite any error, the appeal must be dismissed.[3]
[3] Fox v Percy (2003) 214 CLR 118, [29] (Gleeson CJ, Gummow and Kirby JJ); Lacey v Attorney-General of Queensland (2011) 242 CLR 573, [56]-[57] (French CJ, Gummow, Hayne, Crennan, Kiefel and Bell JJ); R v Taylor [2014] SASCFC 112, [16] (Stanley J, with whom Kelly and Peek JJ agreed).
The appellant’s four grounds of appeal may be summarised as follows:
1.The trial judge erroneously equated the concept of “wrongfulness” under s 269C(1)(b) of the CLCA with “naughtiness” and “cheekiness” with the result that he failed to apply the correct legal test when assessing the question of mental incompetence and the evidence of Professor Young and Ms Heinrich.
2.The trial judge’s finding that the appellant was mentally competent cannot be supported having regard to the evidence of Professor Young and Ms Heinrich.
3.There was a denial of procedural fairness because the trial judge made factual findings which were not based on any challenge made in cross-examination or which were otherwise unsupported by the evidence.
4.The trial judge’s reasons were inadequate because his reasoning was flawed and significant intermediate factual findings were unsupported by the evidence or based on matters not before the Court.
The appellant contended that this Court should accept the evidence of the experts on the balance of probabilities and substitute a finding that the appellant was not mentally competent.[4]
[4] R v Sexton [2018] SASCFC 28, [177] (Kourakis CJ, with whom Peek and Nicholson JJ agreed).
As will be seen, in the circumstances of this case, that course is not open.
Two preliminary matters - miscarriage
Two issues about the conduct of the trial must be noticed at the outset. These emerged shortly before the hearing of the appeal and were not really embraced by the grounds of appeal. They tend to demonstrate why the mental competence investigation miscarried.
The first concerns the legal test which was applied, being the current test applicable under s 269C(1)(b) of the CLCA, and the second concerns the basis upon which evidence was received by the court at the trial of the issue of the appellant’s mental competence.
The wrong legal test was applied

In her outline for this appeal, counsel for the respondent pointed out that the parties and the court had applied the wrong version of s 269C(1)(b) of the CLCA. At the hearing of the appeal, counsel for the appellant accepted that the legal test which was applied was the wrong test. Given the substantive nature of the relevant provision, it was accepted that the earlier iteration of s 269C(1)(b) applied to this case, which was in the following terms:[5]
[5]     Examples of the application of the earlier test are provided by R v Rasmussen [2018] SASC 164, [261] (Bampton J); R v Cawte [2018] SASC 182, [5]-[6] (Nicholson J); Nadebaum v Police [2020] SASC 23, [6] (Lovell J).
269C—Mental competence
(1)A person is mentally incompetent to commit an offence if, at the time of the conduct alleged to give rise to the offence, the person is suffering from a mental impairment and, in consequence of the mental impairment—
(a)     does not know the nature and quality of the conduct; or
(b)     does not know that the conduct is wrong; or
(c)     is unable to control the conduct.
Instead, the trial judge had been invited to proceed on the present iteration of s 269C(1)(b) which only operated from 23 October 2017, after the period of the alleged offending.[6] The present iteration of s 269C(1)(b) is as follows:
[6]     Criminal Law Consolidation (Mental Impairment) Amendment Act 2017 (SA) (No 19 of 2017), s 6.
269C—Mental competence
(1)A person is mentally incompetent to commit an offence if, at the time of the conduct alleged to give rise to the offence, the person is suffering from a mental impairment and, in consequence of the mental impairment—
(a)     does not know the nature and quality of the conduct; or
(b)     does not know that the conduct is wrong; that is, the person could not reason about whether the conduct, as perceived by reasonable people, is wrong; or
Note—
Paragraph (b) adopts the test as stated and excludes from consideration whether the defendant could reason with a moderate degree of sense and composure as set out in R v Porter (1936) 55 CLR 182.
(c)     is totally unable to control the conduct.
As is made clear by the note to s 269C(1)(b), the present iteration removes from consideration what has been described as the “Porter gloss”.[7] In R v Porter Dixon J explained that it was relevant to consider whether, at the time of the offending, the accused could not reason with a moderate degree of sense and composure about his offending:[8]
The question is whether he was able to appreciate the wrongness of the particular act he was doing at the particular time. Could this man be said to know in this sense whether his act was wrong if through a disease or defect or disorder of the mind he could not think rationally of the reasons which to ordinary people make that act right or wrong? If through the disordered condition of the mind he could not reason about the matter with a moderate degree of sense and composure it may be said that he could not know that what he was doing was wrong. What is meant by “wrong”? What is meant by wrong is wrong having regard to the everyday standards of reasonable people.
[7] R v Lado [2020] SASC 223, [7] (Nicholson J); Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135, [111], [124]-[127] (Livesey JA).
[8] R v Porter (1933) 55 CLR 182, 189-190 (Dixon J).
In a case such as this, that would require that consideration be given to whether, by reason of the appellant’s mental impairment, he could not reason about sexual offending with under-age males with a moderate degree of sense and composure.
The present iteration also adds the word “totally” to s 269C(1)(c). The present iteration of s 269C(1) is in these respects therefore more demanding of an accused who puts mental competence into issue.
Though senior counsel for the appellant expressed some embarrassment about having applied the wrong test, the respondent submitted that the application of the wrong test did not operate to the detriment of the appellant. That bold submission was based on the proposition that, as the psychologists had concluded that the appellant was unable to reason at all, and therefore could not reason whether his conduct was wrong in any sense, their evidence would have been no different even if they had been required to consider whether the appellant could not reason with a moderate degree of sense and composure.
Whilst in a sense that may be so, that does not properly address the question whether the application of the wrong test has operated to the detriment of the appellant. Indeed, because it is clear that the present iteration of s 269C(1)(b) is more demanding of a defendant who is seeking to establish mental incompetence, it cannot be assumed that the failure to apply the less demanding statutory test for the determination of mental incompetence has not operated to the appellant’s detriment.
In circumstances where the trial judge rejected the opinion evidence of the psychologists, because he was not satisfied about their view that the appellant was wholly unable to reason about whether his conduct was wrong, it cannot be assumed that the trial judge would have taken the same approach if both he and the psychologists had addressed whether the appellant could not reason with a moderate degree of sense and composure.
On this basis alone, and notwithstanding that this was the approach taken by the appellant at trial,[9] permission to appeal should be granted and the appeal allowed.
The parties were in dispute about the evidence before the court
[9] KBT v The Queen (1997) 191 CLR 417; Fingleton v The Queen (2005) 227 CLR 166, [83] (McHugh J) citing Pemble v The Queen (1971) 124 CLR 107; Perera-Cathcart v The Queen (2017) 260 CLR 595, [124] (Nettle J); Orreal v The Queen (2021) 274 CLR 630, [16] (Kiefel CJ and Keane J).
As for the evidentiary basis on which the trial proceeded, the appellant pointed to pre-trial correspondence in which the prosecution conceded that there was no issue about the diagnosis of each expert, nor that the diagnosis of ASD constituted a “mental illness” and, thereby, a “mental impairment” for the purposes of ss 269A(1) and 269C(1) of the CLCA.
The appellant contended that the prosecution only put into dispute the application of the relevant legal test by each expert. This was said to have been the basis upon which the appellant conducted the hearing. It followed, said the appellant, that the prosecution took no issue with the material on which the diagnosis was based, including the history provided by the appellant and his mother.
By contrast, the respondent took issue with the failure by the appellant to prove the facts underlying the opinions of Professor Young and Ms Heinrich in circumstances where neither the appellant nor his parents gave evidence. The respondent maintained that the failure to prove the factual basis for the expert opinion evidence undermined its efficacy, quite apart from the flawed reasoning and failures by the experts to properly apply the statutory test concerning the question whether the appellant was mentally incompetent by reason of ASD.
Whilst it will be necessary to return to the way in which the expert evidence was led in this case, it is sufficient to say at this point that at the hearing before the primary judge the parties were not ad idem regarding their approach to the evidence. The admission of the evidentiary material at the trial was marked by silence from each party, and their misunderstandings did not emerge until the hearing of this appeal. Had there been oral final addresses and had the disagreement concerning the evidence emerged during those addresses, it may have been possible to require that witnesses be called or recalled, as the case may be. In circumstances where the disagreement between the parties cannot fairly be resolved by resort to questions of onus, or by a reading of the transcript, the written submissions and the reasons taken as a whole, this Court cannot resolve that disagreement.
Given the existence of an irreconcilable dispute about whether and to what extent the factual basis upon which the experts expressed their opinions concerning mental incompetence was proved, this is not a case where it is open to this Court to have regard to the whole of the record and then form its own views. The hearing miscarried. Regrettably, a re-trial is necessary.
Whether and to what extent the facts can be agreed, or witnesses must be called, will need to be determined by the parties before the trial resumes. Whilst the issue is not likely to be the appellant’s diagnosis of ASD, but whether in consequence of that mental impairment the appellant was affected in the manner specified in (a), (b) or (c) of the earlier iteration of s 269C(1), that will ultimately turn on a clear-sighted analysis of what evidence is to be adduced and the basis for its admission. That will require that the parties confer and not merely exchange correspondence.
It will be of the first importance at the new trial that the parties and the court clearly identify the evidentiary basis upon which the trial is to proceed at the time of tender, including the facts upon which the expert opinion evidence is to be led or challenged.
The tender of the prosecution evidence in this case
Whilst the trial judge recorded the prosecution case in his reasons, as revealed by its affidavit evidence concerning the objective circumstances of the offending, he said that he did so only on the basis that these were “factual allegations and … not proven facts”.[10] The five pages of reasons outlining the factual narrative of the appellant’s alleged offending which followed, earlier summarised, were strictly unnecessary if the narrative did not represent evidence which had been proved for the purposes of the hearing.
[10] R v BGC [2022] SADC 54, [9].
The statement that the prosecution evidence was not proved sits awkwardly with the absence of objection from the appellant at the time of tender. The absence of objection at the time of tender suggested that this evidence was proved on the basis that it represented the evidence that the prosecution witnesses, including the complainants, would have given if called, even if only for the purposes of the mental competence investigation.
The absence of objection also suggested that the prosecution evidence was available to be considered by the experts and the court when evaluating the question of mental competence.
Whatever may have been the intention of the parties, it was not articulated for the benefit of the trial judge at the time of tender and it was not the basis upon which the trial judge said that he took the prosecution evidence into account.
The tender of the expert opinion evidence in this case
More troubling still, the expert reports which contained the expert opinion evidence upon which the appellant relied were also tendered without objection. Again, at the time of tender nothing at all was said. No clarification was given as to whether or to what extent the histories stated in those reports were admitted or, by contrast, otherwise needed to be proved by other, admissible evidence from the appellant.
The histories relied on by the expert psychologists were obtained during their examinations from the appellant and, at times, his parents. No attempt was made to call evidence from them. Those histories were, together with formal testing and examinations, relied on by the psychologists for the purposes of providing their expert opinion evidence.
In this case, the appellant’s complaint is that as the expert opinion evidence was admitted without objection, and on the basis that the ASD diagnosis was conceded, the factual basis for the diagnosis, the histories, must likewise have been conceded.
It may be accepted that, in some cases, the failure to object at the time of tender may be taken to amount to acquiescence in the admissibility of expert opinion evidence, including the factual assumptions upon which it is based. For example, in Boothy v Morris, the Full Court held:[11]
Where the opinion of an expert is based upon a factual foundation that factual foundation must in general be proved to the Court by admissible evidence and, to the extent that an opinion is based upon a supposedly factual foundation which is not established by evidence, it is to be disregarded by the Court. Nevertheless, the parties to any litigation are bound by the course of the trial. It often happens in civil trials that parties allow opinions to be expressed upon the basis of information which is not proved in Court. That is often a sensible course which facilitates the trial and minimises the cost of the trial and is to be encouraged rather than discouraged.
If a party wishes to contend that an opinion is unacceptable because it is based upon a factual foundation which has not been established and will not be established, it is incumbent upon the counsel for that party to take the objection when the evidence is tendered or at least to make it clear before the close of the case of the opposite party …
[11] Boothy v Morris [2002] SASC 126, [39]-[41] (Mullighan J, with whom Doyle CJ and Williams J agreed), citing Scuteri v Wood (1987) 137 LSJS 7, 9 (King CJ).
Whilst that was a statement made in the course of civil litigation, the parties in a criminal case may explicitly or by acquiescence agree the factual basis upon which an expert opinion is to be received by the court.
However, in this case, though no objection was taken when the opinions of the psychologists were tendered, the cross-examination of the experts made it clear that the prosecution was not accepting a number of the matters which had been assumed by the psychologists. In addition, the reasoning and opinions of the psychologists were put squarely into issue during cross-examination. That emerges from a reading of the cross-examinations as well as from the reasons of the trial judge.
No objection was taken by the appellant to the challenges made by the prosecution in cross-examination, particularly the challenge made to the factual basis or history on which the psychologists called by the appellant had relied. This therefore is not a case where it can be said that the prosecution had explicitly or by acquiescence agreed the factual basis on which the experts had relied. The appellant bore the burden of proof on the balance of probabilities.
In the result, on a number of issues there remained conflicts between the accounts given by the appellant to the police or the experts, when compared with the evidence given by the complainants. How those conflicts were to be addressed and resolved by the court was not addressed by the parties, whether at the time the expert reports were tendered or in their written final addresses.
In consequence, the reasons contain no clear statement of findings about those facts which the trial judge accepted, and those facts which the trial judge rejected, for the purposes of evaluating the expert opinion evidence before him.
Accordingly, it would appear that there was a failure by the parties to agree or address the proof of the assumptions upon which the expert opinion evidence was based or was to be criticised. That is an issue which at common law usually goes to admissibility and not merely the weight to be accorded to the expert opinion evidence.[12]
[12] Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588, [66] (Heydon J). See also Ramsay v Watson (1961) 108 CLR 642; R v Bonython (1984) 38 SASR 45, 46-47 (King CJ); Paric (Constructions) Pty Ltdv John Holland (1985) 62 ALR 85, 87‑88; R v Fowler (1985) 39 SASR 440, 443 (King CJ); and R v Bjordal (2005) 93 SASR 237.
The trial judge’s reasons regarding the expert opinion evidence in this case
The trial judge received expert opinion evidence in the form of a bundle of written reports from the two psychologists earlier mentioned, Professor Young and Ms Heinrich. Professor Young was retained by the solicitors for the appellant. Ms Heinrich examined the appellant pursuant to an order of the court.
It was apparent from the history obtained by Professor Young that the appellant had been seeing a psychiatrist since he was 20 years. There was no evidence about the opinions of or treatment by that psychiatrist. There was, however, evidence that the appellant was being medicated for depression and Obsessive Compulsive Disorder.
Professor Young diagnosed the appellant with ASD pursuant to the criteria set out in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, published by the American Psychiatric Association (DSM-5). Ms Heinrich agreed with that diagnosis. According to the evidence before the trial judge, individuals with ASD may be predisposed to “crime commission”:[13]
… research indicates that four factors predispose ASD individuals to crime commission including social naivety, aggression triggered by disrupted routine, aggression due to social misunderstanding and obsessive behaviour with lack of understanding of the implications of that behaviour. Lack of empathy, inability to consistently control emotions and issues associated with moral reasoning can increase in an ASD individual exposed to the criminal justice system.
Professor Young accepted that during his life, the accused has found it difficult to initiate conversations and would steer conversations towards things that interested him, whilst avoiding conversations that did not interest him. He had deficiencies in developing, maintaining and understanding relationships. He had difficulties adjusting his behaviour to suit different social contexts. … Some information was received about the history of the accused’s childhood in Zimbabwe and when he was very young, there was an event of his home being surrounded. … When he reached Australia and when in high school, he was placed in a higher level for his age due to his intellect. He was bullied, called names and ended up mixing with a group at the bottom of the social hierarchy. He socialised with children in year levels below him because they teased him less …
[13] R v BGC [2022] SADC 54, [46]-[47].
In the course of undertaking a very detailed analysis of the opinions expressed by the psychologists, the trial judge expressed a number of criticisms of their reasoning and the assumptions they made. In the case of Professor Young, the trial judge recorded her views and his concerns about those views:[14]
Professor Young opined that the accused did not know that the conduct was wrong and this was because he had ASD and had been raised in a “cult-like” environment. She accepted at face value what the accused told her that boys in the religious group engaged in sexual exploration and it did not occur to him that as an adult of between 21 and 24 years of age, nothing he did to those children was in any way against the law. Professor Young appears to have accepted that the accused had never been educated that masturbation was something not necessarily shared with other people. In contrast and if that was his belief and understanding, there is no evidence that he has ever engaged in the practice in any place other than in secret and away from the supervision and the awareness of the parents of these children. No consideration appears to have been given to the fact that the accused was not more publicly promiscuous in his behaviour. He did not perform any of this behaviour in public, openly in his home nor did he inform his family about it or what he thought about it. These were all decisions made by him and it therefore appears that he had a reason to reason that to do so may, for example, offend bounds which he understood.
[14] R v BGC [2022] SADC 54, [59].
The trial judge was critical of the research undertaken by Professor Young into the appellant’s church, together with her conclusion that it was “cult-like”:[15]
Professor Young placed particular emphasis upon the experience of the accused in the church of which his family is a member. It is a church of strict rules including the manner in which members should act in everyday life such that members are encouraged to remove themselves from worldly influences. Notwithstanding, the accused’s parents allowed him a few ‘unscrupulous’ belongings such as computer games, DVDs and games but these were hidden when other members of the church attended.
Professor Young appears to have then conducted her own research about this group. It is not clear to me whether or to what extent she applied the appropriate rigour to the undertaking of this research to ensure its accuracy, its status, whether it would meet appropriate standards or whether it was accurate at all. This is regrettable… Professor Young had a meeting with the mother of the accused. She appears not to have asked her or the accused anything about the church group, notwithstanding, she was prepared to say that it might be viewed by people outside the church as a cult. It is unclear to me what relevance she was then placing upon the information about this church.
[15] R v BGC [2022] SADC 54, [68]-[69]. See also [73].

A number of these criticisms do not appear to have been squarely put to Professor Young for her response during the hearing.
In the case of Ms Heinrich, the trial judge referred to her opinions and the challenge made to them in cross-examination, before recording:[16]
In the end, Ms Heinrich accepted, as must be the case, that if the accused had received any education in Australia about the age of consent, that masturbating boys under the age of 17 was illegal and wrong, then he must have committed the offending in circumstances where he could reason it was wrong. If he had been educated on the age of consent, then there was nothing about having ASD that deprived him of reasoning that masturbating underage boys was also wrong.
[16] R v BGC [2022] SADC 54, [84].
In this part of his Honour’s reasons, 15 pages comprising an admixture of what the experts stated in their reports, their responses to questions put to them during cross-examination, and criticisms made by the trial judge, the precise factual basis upon which the experts based their opinions was not identified and no clear findings were made about those factual assumptions.
The trial judge observed that the histories obtained by the psychologists were, in various respects, inconsistent with the accounts given by the complainants. The trial judge took that conflict into account when criticising their opinions. For example, in the case of Professor Young, the trial judge was critical of her failure to detect the inconsistency between the appellant’s history and the accounts of the complainants as to whether it was the appellant who instigated the sexual activity. Professor Young was asked whether she was aware of inconsistencies between the account provided by the appellant, and the accounts provided by the complainants.[17] This was addressed in Professor Young’s report, to an extent, by her observation, “I cannot say why other than someone is not telling the truth.”[18] As to this, the trial judge said:[19]
Professor Young then turned her attention to the accused’s account of the incident and the accusations. She appeared to accept the accused’s explanation that the persons with whom he committed these offences were friends he made within the church, all of whom were very much younger than he and whom he said always had conversations that were smutty in nature and would behave in a sexual manner.
He said he never instigated the behaviour but that is inconsistent with the statements made by the complainants. Professor Young does not seem to have detected this inconsistency. He told her that he did not challenge the behaviour because that is “what guys do” and therefore he thought it was normal and reasonable behaviour. He assumed, therefore, that there was some consensus about masturbation. It was thought to be “naughty” and “taboo”. No delineation appears to have been made about what was apparently “normal” behaviour that is, what guys do and what is “naughty and taboo” behaviour, or for how long children growing through puberty to maturity would openly behave in that way.
[17] Transcript of Proceedings, R v BCG (District Court of South Australia, DCCRM-20-154, Judge Slattery, 3 February 2022), 54-55. Professor Young said that she and the appellant “spoke a bit about that”, “just general conversation”. She said that it did not change her opinion.
[18] Report of Professor Young (5 January 2022), 6.
[19] R v BGC [2022] SADC 54, [71]-[72].
A clear distinction may be drawn between a criticism which might be made of an expert who is prepared to accept, without analysis or critique, what an accused says by way of history, and a failure by that expert to take account of other information which is available to the expert which is inconsistent with the accused’s history. In the passage cited, the trial judge appears to be making both criticisms. In theory, depending on the aspect of the history concerned, there can be no complaint about the first criticism.
However, the second criticism is at best problematic. It is problematic for at least two reasons. First, this is a case where the accounts of the complainants were only treated as “factual allegations and … not proven facts”.[20] If the accounts of the complainants were not before the court as proven facts, whether the experts took account of them could not be addressed other than in a very general way. Secondly, the criticism misunderstands both the role of the expert and the function of the factual assumptions made by the expert for the purposes of giving expert opinion evidence. As will be explained, on the question of the appellant’s history the experts cannot and should not engage in fact-finding. That is not their role. That remains the role of the trier of fact, here the trial judge.
[20] R v BGC [2022] SADC 54, [9].
The response of Professor Young was an appropriate response. If the significance of a history different to the one she had been given was to be considered, the cross-examiner was required to ask the Professor to set aside the history she had been given and to consider a different history.
In cases such as these, when an alternative history is put to the expert the expert must be invited to address whether the new history is different to what had been assumed, as well as whether the difference affects the expert’s opinion. For example, if the difference suggested that someone was not telling the truth, and if the expert is asked to assume that it is the accused who was not telling the truth, then it was appropriate to ask whether the accused’s lack of credibility or veracity affects the expert’s expression of opinion that the accused lacked mental competence. Further questions could then be asked about these matters. One topic might be the significance of the accused not telling the truth about the circumstances of the offending. The cross-examiner might explore the issue whether that could be because the accused recognised that what the accused had allegedly done was wrong. The scope of the questioning would be a matter for the cross-examiner’s instructions, exercise of judgment and own expert advice, as well as the answers given. Ultimately, however, it would be necessary to put to the expert that, if the alternate history was correct, then the expert could not conclude that the accused lacked mental competence at the time of offending.
The question as to which history should be accepted by the trier of fact, or to what extent it should be accepted, often has an important bearing on the expert opinion evidence. In this way it can be seen that the acceptance or rejection of the expert opinion may often depend, at least in part, on resolving any underlying factual dispute on which it rests. That was not done in this case.
In this case, although both psychologists concluded that, by reason of his mental impairment, the appellant did not understand the wrongfulness of his conduct, the trial judge found that he was not assisted by these opinions in reaching his conclusion.[21] The implication is that the trial judge did not agree with these opinions, but he did not make it clear whether he regarded them as simply wrong, or as inadmissible because they were unsupported by the evidence, or of little weight, or a combination of these matters and, in each case, why he took those views.
[21] R v BGC [2022] SADC 54, [103].
An investigation into mental competence under Part 8A
In order to rebut the presumption of mental competence in s 269D, an investigation must be conducted under Division 2 of Part 8A and a finding of mental incompetence made pursuant to s 269C(1) of the CLCA.
The accused bears the onus of establishing that he had a mental impairment (here, a mental illness, ASD) and that he was, in consequence, not mentally competent at the relevant time - he who asserts must prove[22] - and this must be positively made out on the balance of probabilities.[23]
[22] Commonwealth v Muratore (1978) 141 CLR 296, 303 (Murphy J).
[23] R v Leach [2002] SASC 321, [13]-[14] (Bleby J, with whom Debelle and Williams JJ agreed).
The appellant may elect to have the investigation dealt with by a judge sitting alone pursuant to s 269B(1) of the CLCA.
Section 269E(2) confers a discretion on the trial judge to first proceed with a trial of mental competence, rather than a trial of the objective elements of the offence.[24] When that occurs, the trial must proceed pursuant to s 269F. A trial of mental competence requires that the court hear relevant evidence and representations put by the prosecution and the defence under s 269FA(1) of the CLCA.
[24] See generally Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135, [39] (Kourakis CJ), [201]-[207], [210] (Livesey JA). The requirement that mental incompetence be established on the balance of probabilities is made clear by s 269FA(3) of the CLCA. That may be contrasted with the need to prove the objective elements of the offence beyond reasonable doubt, see s 269FB(2) of the CLCA.
The court may also require, as it did in this case, that the defendant undergo an examination by a psychiatrist or other appropriate expert, see ss 269FA(1)(b) and 269FA(2).
At the conclusion to the trial of mental competence the court must record findings in the manner specified by s 269FA(3), or dispense with the investigation and record a finding of mental incompetence, s 269FA(5) of the CLCA.
Expert opinion evidence in a mental competence investigation
Although the accused bears the burden of proving that he lacked mental competence it is usual, as was done in this case, for the prosecution to commence by opening on the nature of the prosecution case and the material available to prove that case. The accused will then adduce the material relied on to demonstrate mental incompetence, typically a combination of the accused’s evidence and expert opinion evidence. The prosecution will then tender any material on which it relies for the purposes of the investigation into mental competence.
When considering the admission of evidence in South Australia, including expert opinion evidence, it is necessary to apply the common law as regulated and supplemented by the Evidence Act 1929 (SA). The proper approach to the tender of expert opinion evidence has been considered in this context on a number of occasions.[25]
[25] See, by way of example, the cases collected in NBM v The Queen [2021] SASCA 105, [39]-[43] (Lovell JA, in dissent as to the outcome); Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135, [188]-[197], [265] (Livesey JA).
The fundamental principle is that the admissibility and purpose of expert opinion evidence is to assist the court to form a sound judgment on matters requiring specialised knowledge or expertise. The expert must have the relevant knowledge and expertise and be capable of expressing an opinion on a matter on which the court requires assistance. As was explained by Dixon CJ in Clark v Ryan:[26]
The rule of evidence relating to the admissibility of expert testimony as it affects the case cannot be put better than it was by J. W. Smith in the notes to Carter v. Boehm, 1 Smith L.C., 7th ed. (1876) p. 577. "On the one hand" that author wrote, "it appears to be admitted that the opinion of witnesses possessing peculiar skill is admissible whenever the subject-matter of inquiry is such that inexperienced persons are unlikely to prove capable of forming a correct judgment upon it without such assistance, in other words, when it so far partakes of the nature of a science as to require a course of previous habit, or study, in order to the attainment of a knowledge of it." Then after the citation of authority the author proceeds: "While on the other hand, it does not seem to be contended that the opinions of witnesses can be received when the inquiry is into a subject-matter the nature of which is not such as to require any peculiar habits or study in order to qualify a man to understand it." Adopted by Harding A.C.J. in Reg. v. Camm.
In R. v. Parker, one of the cases establishing the evidentiary use of finger prints to prove identity, Cussen J. in that connexion said that expert witnesses may give in evidence statements based on their own experience or study but that they cannot be permitted to attempt to point out to the jury matters which the jury could determine for themselves or to formulate their empirical knowledge as a universal law.
(Footnotes omitted)
[26] Clark v Ryan (1960) 103 CLR 486, 491 (Dixon CJ).
Expert opinion evidence is only admissible if it satisfies the common law rules relating to its admission, together with any rules of court, practice directions or codes of conduct that apply to the particular forum in which the opinion is to be elicited.[27]
[27] See the Uniform Civil Rules 2020 (SA), Ch 7 Pt 14 Divs 3-4 and the Joint Criminal Rules 2022 (SA), Ch 2 Pt 11 Divs 1-2 for the harmonised rules as to the obligations of an expert and the content of an expert report.
In the context of an ordinary criminal trial, King CJ addressed the common law requirements in the following way:[28]
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. Ryan. 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 tor Government Transport v. Adamci), 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.
(Footnotes omitted)
[28] R v Bonython (1984) 38 SASR 45, 46 (King CJ). See also Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705, [84]-[86] (Heydon JA).
Moreover, expert opinion evidence is not usually admissible at common law unless the constituent facts on which it is based are properly proved by admissible evidence.[29]
[29] See generally the decisions of Heydon JA in Makita v Sprowles (2001) 52 NSWLR 705 and Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588, and also Trade Practices Commission v Arnott’s Ltd (No 5) (1990) 92 ALR 527, Arnott’s Ltd v Trade Practices Commission (1990) 97 ALR 555, 589-598 and R v Fowler (1985) 39 SASR 440, 443 (King CJ).
It is a standard jury direction that where expert opinion evidence is unchallenged, the jury, while not obliged to act on the evidence, must not capriciously disregard it. Relevant factors in assessing expert opinion evidence include whether the expert is suitably qualified, whether the assumed facts underpinning the opinion are proved, and if proved form a proper basis for the opinion, and whether the expert has given their evidence in a partial or impartial manner.[30]
[30] Taylor v R (1978) 45 FLR 343; R v NCT (2009) 26 VR 247, 253 (Nettle JA); Makita (Australia) Pty Ltd v Sprowles (2001) 52 NSWLR 705, [85] (Heydon JA).
On a trial by the judge alone, all of these factors remain relevant and, in addition, it is for that judge to write reasons that explain how any decision was reached concerning the acceptance or rejection of the expert opinion evidence. A capricious, unreasoned rejection of expert opinion evidence is likely to be viewed adversely on appeal. That is not to say that the evidence cannot be rejected. It can, but there must be a proper basis articulated for doing so. That said, a judge cannot simply reason that, because two experts agree that an accused was mentally incompetent to offend, the judge has no role to play in exercising an independent judgment. The judge must exercise independent judgment, both as to the facts and the matters of expert opinion, for a decision about mental competence to commit crime cannot be “outsourced” to experts.
Evidence from a properly qualified, objective expert is generally more reliable than a lay person’s opinion (whether or not that person is a judge) on a matter of specialised knowledge and expertise because the expert usually has more experience and better expertise relevant to the evaluation required. An expert’s experience and training will often assist the court in a case such as this because it is usually necessary to evaluate the functioning of an accused. For example, is that functioning best explained by the fact that the accused is incapable of reasoning rationally by reason of mental impairment, or is it compatible with the conduct that might be expected from a person of sound mind? The proper determination of issues such as these must be approached with care: [31]
In cases of this kind it may well happen that expert witnesses accepting the hypothesis that a prisoner is insane are not on the same ground as counsel adopting the opposite hypothesis and arguing according to the common sense of ordinary men supplied by the experience of sane persons.
[31] Mizzi v The Queen (1960) 105 CLR 659, 663 (Dixon CJ, McTiernan, Fullagar, Menzies and Windeyer JJ).
In practice it is rare for an expert to give an opinion on facts which are wholly assumed. Whilst an expert, particularly in cases involving psychological or psychiatric evidence, will give emphasis to the history taken by the expert from the accused in forming an opinion, there are usually other sources of information. The expert may also rely on supplementary history from the accused’s family, as well as written records such as medical and hospital notes. The expert will usually have also relied on the clinical impression formed by observing the accused during the examination. Like demeanour for the trial judge, that impression may or may not be both reliable and important to the formation of the opinion. As well, the expert may have performed a physical examination and administered tests, such as psychological tests. Undertaking investigations such as these, a commonly accepted practice, may mean that the expert must give evidence of some factual matters even though the expert must express any opinion on the basis of those and the history. The history represents an assumed set of facts that may or may not correlate with the facts as found by the trier of fact.[32]
[32] Ramsay v Watson (1961) 108 CLR 642, 645 (Dixon CJ, McTiernan, Kitto, Taylor and Windeyer JJ).
In this case, it is necessary to emphasise both the necessity for the expert opinion evidence to be based upon the facts acceptable to the trier of fact and, in addition, that it is rare for all primary factual material to first be elicited before the expert opinion evidence is addressed with the benefit of that material:[33]
In an Arcadian forensic setting, if expert evidence is to be used, a party would first put its primary factual material before the court either in chief or in the course of cross-examining its opponent’s witnesses and then call expert witnesses to express opinions based on assumptions of fact that that party claimed the court would find proved to its satisfaction on the evidence. In practice that order of events is rare.
[33] Rhoden v Wingate (2002) 36 MVR 499, [1] (Sheller JA); see also Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588, [81]-[90] (Heydon J).
This means that it is necessary for the parties and the court to be careful to ensure that the factual assumptions upon which expert opinion evidence is based are made clear. Clarity and precision in the identification of the facts will facilitate identification of what it is that must be proved in order to properly support the expert opinion evidence:[34]
The requirement to identify the assumptions or facts upon which expert opinion evidence is based is not met by handing an expert witness a bundle of statements, or a transcript, and then asking what the expert thinks about the case, or some aspect of it, such as whether an available defence is made out.
[34] Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135, [192] (Livesey JA).

In consequence, it is particularly important that the parties give careful thought to, and confer about, the evidence to be put before the court and the experts, so that it is analysed and capable of distillation into discrete factual propositions. In many cases that can result in a statement of agreed facts, or at least a clear understanding of the limits of any agreement made about the facts and the basis upon which evidence is to be received by the court, as well as the extent of any conflicts that must be resolved.
That did not occur in this case. It was incumbent on the parties in this case to make their respective positions clear at the time the evidence was tendered before the court or, at the latest, before the close of the opponent’s case.
So far as the prosecution evidence in this case is concerned, proper practice required that it be made clear that the affidavit evidence was tendered for the purpose of proving the truth of the complainants’ accounts in connection with the investigation into mental competence. At the same time, proper practice required that the appellant make clear whether tender was accepted for that purpose, without also requiring that the prosecution call its witnesses. Ideally, at that stage or in his own opening, the appellant would also make it clear that, in the event of any conflict, the court would be invited to prefer the appellant’s history on which his experts had relied.
As for the appellant’s case, proper practice required that at the time of tender of the expert opinion evidence, the appellant address whether and to what extent he was going to prove the histories on which the psychologists had based their opinions. The prosecution was, at that same time, required to indicate whether it accepted the factual basis for those opinions or required that the histories be formally proved in the usual way by calling evidence from the appellant and any other relevant witnesses, such as his parents. Strictly, tender could then have been made subject to an undertaking to call the accused or his parents, or both the accused and his parents.[35]
[35] Dasreef Pty Ltd v Hawchar (2011) 243 CLR 588, [81]-[82] (Heydon J).
So, in many cases it will be necessary for the accused to go into evidence in order to lay the factual foundation for the histories on which the experts who have examined the accused relied.[36] In many cases there will be an issue as to whether the accused’s evidence matches the assumed factual basis. As has been explained:[37]
It is a question of fact whether the case supposed is sufficiently like the one under consideration to render the opinion of the expert of any value.[38] In any case, but particularly in a criminal case, it is very important that the assumptions of fact upon which the opinion is given be clearly stated and that the evidence be confined to opinions expressed upon those assumed facts. The validity of the opinion in a criminal case is necessarily dependent upon the acceptance “of those facts at least as a reasonable possibility and that to the extent that the assumed facts are not so accepted the [trier of fact] should consider the extent, if any, to which such validity as the opinion might otherwise possess is affected by [the] non-acceptance of any of the assumed facts”.[39]
[36] Ramsay v Watson (1961) 108 CLR 642.
[37] NBM v The Queen [2021] SASCA 105, [42] (Lovell JA).
[38] Paric (Constructions) Pty Ltd v John Holland (Constructions) Pty Ltd (1985) 62 ALR 85, 87-88 (Mason ACJ, Wilson, Brennan, Deane and Dawson JJ).
[39] R v Fowler (1985) 39 SASR 440, 443 (King CJ).
Nevertheless, where the parties proceed before a judge alone, a degree of informality may be adopted regarding the tender and proof of expert opinion evidence. Whilst there can be no objection to that in principle, it remains necessary that the parties explicitly address the basis upon which the evidence is tendered, including whether the factual basis for the expert opinions must be formally proved. Expedition cannot be permitted to trump fairness to both parties in connection with the just resolution of a dispute about mental competence.
There may be cases where the prosecution is prepared to concede that the histories recorded in the expert reports reflect the evidence that the accused would give if called, without also requiring that the accused be called for the purposes of cross-examination. Proper practice would nonetheless require that the prosecution clearly indicate whether it is intended to challenge the factual basis revealed by those histories, or some part of them, as well as the expert reasoning and opinions which rest on those facts. Similarly, proper practice would require that the accused clearly indicate whether any conflicting evidence from the prosecution would be challenged, even if this was not to be by cross-examination.
It would accordingly be necessary that the parties make it clear to the court whether they were each content to rely on the examination and cross-examination of the experts, as well as the inferences and probabilities arising on any differing factual accounts, for the purpose of determining whether, on the balance of probabilities, the accused had proved his mental incompetence at the time of the offending.
Proceeding in that way in this case would have made it clear to the court and the parties that the investigation into mental competence was to proceed on the basis of a conflict in the evidence, including as to some aspects of the factual basis for the expert opinion evidence, but that neither party required the other to call its witnesses. Nonetheless, this would not have obviated the need for the parties to identify whether and to what extent the factual basis for the expert opinion evidence had been established, or was undermined and, in consequence, that it was necessary for findings to be made by the court about that factual material and the effect those findings might have on the expert opinion evidence.
As may be obvious, whether it is feasible to proceed in this way is a matter for the parties and the court to determine having regard to the particular facts and circumstances of any case. Key considerations will include the nature of the alleged offending, the nature of the mental impairment and the nature and extent of any contest on the facts.
Of course, even should the parties wish to proceed informally it may become apparent that important factual contests cannot properly be decided on conflicting written evidence by recourse to the inferences and probabilities. That may be particularly problematic for an accused, who bears the burden of proof on the balance of probabilities. When problems such as these emerge, there may be no alternative to calling evidence on those contested issues. If there is a large number of contested facts, it may be necessary to consider determining the objective elements first.
For example, in this case the question about whether the appellant recognised that what he did was wrong might have been thought to be bound up in subsidiary factual questions such as his understanding about the age of consent in Australia, whether (and if so why) he only ever offended in private, whether he always initiated the sexual activity, and what his reaction was to being told by at least one complainant that what he was doing was wrong. On issues such as these the court may or may not be able to reach a clear view without hearing from the witnesses.
Whilst the appellant was critical of the prosecution given the pre-trial correspondence, there can be no difficulty with the prosecution accepting that a psychiatric diagnosis of a condition recognised by DSM-5 amounts to both a mental illness and a “mental impairment” for the purposes of s 269C(1), without also accepting that, in consequence of that mental impairment, the accused (in this case, on the earlier iteration of s 269C(1)):
(a)     does not know the nature and quality of the conduct; or
(b)     does not know that the conduct is wrong; or
(c)     is unable to control the conduct.
Though there is a clear, logical distinction between the factual basis for a diagnosis of mental illness and mental impairment, and the factual basis for a finding of mental incompetence by reason of that impairment, in practice there is likely to be considerable overlap between those factual bases.
That may require some care in the identification of those facts which are of importance to the determination of mental competence. That is likely to be acute in a case such as this where the relevant mental impairment is, by definition, assessed on a spectrum.
Where a person with ASD should be placed on the spectrum is likely to be important when determining mental competence. Not all of those diagnosed with ASD will perceive events in the same way, nor will they respond in the same way to the same situations. There is likely to be a range of perceptions and responses from those with ASD which depend on a range of matters, such as personality, background and placement on the spectrum. The assessment of mental competence to be made by any expert, and ultimately by the court, will likely depend on assessing in combination the history, the results of formal testing and the clinical impression made during any examination, or in evidence before the court.
In this case, the failure by the parties to clearly identify what was and what was not in issue concerning the factual assumptions upon which the expert opinion evidence was led and, in consequence, the failure of the trial judge to make clear findings about that factual basis, resulted in a miscarriage of the mental competence investigation.
With these observations in mind, the appeal grounds must be addressed, recognising that because there is to be a re-trial it is neither necessary nor appropriate to address all of the grounds advanced.
Appeal ground 1 – the concept of wrongfulness
In the course of his analysis of the opinions of Professor Young, the trial judge was critical of the acceptance by Professor Young, “without further enquiry”, of the accused’s history that he never instigated sexual behaviour but merely joined into the complainants’ masturbatory behaviour because he thought that was “what guys do”. The appellant told Professor Young that he was aware that there was some consensus among the boys that masturbation was ‘naughty’ and ‘taboo’. The appellant also told Professor Young that he never thought that what they were doing was “against the law”.[40]
[40] R v BGC [2022] SADC 54, [56]. See also [72] and [74].
In the “Decision” section of his reasons, the trial judge explained:[41]
The accused understood and told Professor Young that he knew what he was doing was being cheeky or naughty when engaging in the conduct and so he must have understood the nature of the conduct to be naughty when he was committing this offending. It follows he was able to reason about some aspect of the wrongfulness of his conduct and it is not necessary that he knew the conduct was illegal, only that it was wrongful.
[41] R v BGC [2022] SADC 54, [107].
The appellant criticised the reasoning of the trial judge, contending that he had elided the concepts of wrongfulness, naughtiness, and cheekiness. It was submitted that it was inappropriate to add a gloss to the meaning of “wrongfulness” in the sense understood on the authorities.
In support of this submission, the appellant drew on the concept of wrongfulness used in the context of doli incapax when determining the criminal responsibility of a child. The appellant referred to RP v The Queen, where the High Court distinguished knowledge of moral wrongfulness from a child’s awareness that conduct may be merely naughty or mischievous.[42] In that case, the plurality relied upon the analogy drawn by Bray CJ in R v M with the M’Naghten Rules:[43]
In R v M, Bray CJ commenced his analysis of the nature of the knowledge required to rebut the presumption of doli incapax by considering whether it is knowledge that the act is contrary to law, or is wrong judged by the standard of the ordinary person or is wrong according to the child’s subjective and perhaps idiosyncratic ethical standards.[44] His Honour drew an analogy with proof of insanity under the second limb of the M’Naghten Rules, which requires knowledge that the act is wrong according to the principles of reasonable men.[45] The analogy is apt insofar as the knowledge in each case is of the wrongness of the act as a matter of morality and not law.[46] There is, however, in the case of the child defendant, the further dimension of proof of knowledge of serious wrongness as distinct from mere naughtiness.
[42] RP v The Queen (2016) 259 CLR 641, [9] (Kiefel CJ, Bell, Keane and Gordon JJ), [38] (Gageler J). See Rye v Western Australia (2021) 288 A Crim R 174, [51] (Buss P and Mazza JA), [92] (Vaughan JA). See also BDO v The Queen (2023) 97 ALJR 377, concerning evidence under the Criminal Code (Qld) of a child’s capacity to know rather than actual knowledge required at common law.
[43] RP v The Queen (2016) 259 CLR 641, [11] (Kiefel CJ, Bell, Keane and Gordon JJ).
[44] R v M (1977) 16 SASR 589, 590-591.
[45] R v M (1977) 16 SASR 589, 591 citing Stapleton v The Queen (1952) 86 CLR 358, 375 (Dixon CJ, Webb and Kitto JJ).
[46] See R v Chaulk [1990] 3 SCR 1303, 1320.
For the respondent, it was contended that the use of the terms “cheeky or naughty” merely reflected some of the evidence given by the psychologists about what the appellant had said to them when describing his own behaviour. It was submitted that the trial judge did not, thereby, incorrectly state or misapply the requisite test.
The respondent submitted that what might be described as “naughty” may fall at different points on a spectrum between entirely neutral conduct, naughty conduct, and conduct that is relevantly “wrong”. The respondent also submitted that the appellant’s view of his own behaviour demonstrated some understanding that his conduct was not merely neutral but was at a point on the spectrum towards “wrong”. The appellant’s statements gave the trial judge some insight into the appellant’s capacity to appreciate whether his conduct was relevantly wrong.
When conducting a mental competence investigation the court must determine whether the accused was able to appreciate the wrongfulness of the accused’s conduct having regard to the everyday standards of reasonable people.[47]
[47] R v Porter (1933) 55 CLR 182, 189-190 (Dixon J); R v Stapleton (1952) 86 CLR 358; The Queen v Vallance [1964] SASR 361, 369 (Mayo, Chamberlain and Travers JJ); discussed in Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135, [16] (Kourakis CJ), [127] (Livesey JA).
In R v Stapleton the High Court resolved the question whether the accused need understand that the offending conduct was morally wrong, or whether the accused was also required to understand that it was legally wrong. The High Court held that it was sufficient if the accused recognised that the offending conduct was morally wrong:[48]
What appears is that an incapacity to know the difference between good and evil was, if it was the outcome of mental disease, a test of irresponsibility. It is true that among the different expressions used there sometimes appears a defence to knowledge that the act committed was against the “laws of God and man”. But the context leaves no doubt that this expression is referring to the canons of right and wrong and not to criminal law.
[48] R v Stapleton (1952) 86 CLR 358, 368 (Dixon CJ, Webb and Kitto JJ). See also Question of Law (No 1 of 2021) (2021) 140 SASR 135, [127] (Livesey JA).
Regardless whether the “Porter gloss” applies, it may be accepted that, in this context, the requisite meaning of “wrong” is not to be conflated with mere naughtiness.
Nonetheless, it is necessary to pay regard to the whole of the passage in which the trial judge referred to the statement made to Professor Young by the appellant that the appellant knew that what he was doing was “cheeky or naughty”. When that is done it is clear that his Honour was not conflating these terms with the requirement for proof that the appellant did not know that his conduct was wrong in the requisite sense. The trial judge was merely adverting to the appellant’s capacity to reason about “some aspect of the wrongfulness of his conduct”.[49]
[49] R v BGC [2022] SADC 54, [107].
Having said that, and as has been explained, the trial judge’s earlier statement of the applicable test relied upon the wrong iteration of s 269C(1)(b). It will be necessary to address the correct iteration at the re-trial.
Appeal ground 1 should be dismissed.
Appeal ground 2 – the trial judge’s finding cannot be supported
The appellant relied on those authorities which draw a distinction between the approach required of the appeal court under the first limb of the common form criminal appeal provision,[50] and the approach required where it is contended that a verdict is unsupportable having regard to the evidence.[51]
[50] Section 158(1)(a) of the Criminal Procedure Act 1921 (SA), the verdict is unreasonable or cannot be supported having regard to the evidence. See also M v The Queen (1994) 181 CLR 487.
[51] Section 42(5) of the Magistrates Court Act 1991 (SA). See Middleton v Police [2015] SASC 33, [4] (Nicholson J).
Under the common form provision, a verdict cannot ordinarily be set aside unless the court of appeal determines, following its independent review, that it was not open to the trier of fact to be satisfied of guilt beyond reasonable doubt. By contrast, under s 269Y(3) of the CLCA, following its own review the court may substitute its own verdict even if there is evidence to support the finding made by the trier of fact.
The appellant’s case on this ground came close to the proposition that because there was no answering expert opinion evidence from the prosecution, it was therefore uncontradicted.[52] The appellant submitted that it was not open to the trial judge to reject the appellant’s expert opinion evidence. The appellant relied on the following passage from the reasons of Stanley J in R v Taylor:[53]
The trier of fact, whether a judge or jury, is not bound to accept and act upon expert evidence, however, they are not entitled to disregard it capriciously. In deciding the ultimate fact in issue the judge or jury are bound to consider not only the expert evidence adduced but the evidence upon the whole facts and circumstances relevant to the fact in issue.[54] If the expert evidence is all one way and in favour of the accused and there is nothing in the facts and surrounding circumstances which could lead to a contrary conclusion then a verdict against the expert evidence cannot be sustained.[55]
[52] Hone v Western Australia (2007) 179 A Crim R 138, [123]-[128], [150] (Miller JA, with whom Steytler P and Wheeler JA agreed).
[53] R v Taylor [2014] SASCFC 112, [34] (Stanley J).
[54] R v Hall (1988) 36 A Crim R 368, 370-371 (Roden J).
[55] R v Hall (1988) 36 A Crim R 368, 371 (Roden J).
The appellant submitted that there was nothing in the facts and surrounding circumstances which could lead to a conclusion contrary to that expressed by both of his expert witnesses.[56] The appellant attacked the reasoning employed by the trial judge, contending that it failed to recognise the effect of ASD on his capacity to assess whether his conduct was wrong. The appellant relied on the following passage from the reasons of the High Court in Mizzi v The Queen:[57]
The reasoning upon which the cross-examination was based was, of course, the kind of reasoning which a sane mind would pursue, while it is apparent from a reading of the transcript of the evidence that the reasoning of the witnesses was based on the belief or assumption which they adopted that the prisoner's mind was not a sane mind and accordingly would be governed by quite different beliefs and perceptions, and a different consciousness and understanding of the things that would be significant to the sane. In cases of this kind it may well happen that expert witnesses accepting the hypothesis that a prisoner is insane are not on the same ground as counsel adopting the opposite hypothesis and arguing according to the common sense of ordinary men supplied by the experience of sane persons.
[56] Western Australia v Djurasovic [2021] WASC 466, [74]-[78] (Hall J); R v Pesamino [2020] NSWSC 1188, [90] (Wilson J); R v RB [2020] NSWSC 1552, [82] (Wilson J).
[57] Mizzi v The Queen (1960) 105 CLR 659, 663 (Dixon CJ, McTiernan, Fullagar, Menzies and Windeyer JJ).

The respondent countered that it was entirely a matter for the trial judge as the trier of fact to determine what, if anything, he accepted from the experts. The respondent contended that the trial judge was not bound to accept the opinions of the appellant’s experts.
Given the difficulties associated with the factual basis upon which the expert opinion evidence was led and criticised in this case, it is not necessary to finally rule on this appeal ground. However the fact of a re-trial renders it desirable to make some observations about the approach required in a case where the expert opinion evidence appears to be uncontradicted.
As has been explained, the court is not obliged to accept expert opinion evidence even where there is no contrary expert opinion evidence. Even where the parties are agreed, the trier of fact (whether the jury or the judge alone), may not agree with the views expressed by the experts.[58] Nonetheless in cases involving psychiatric evidence it has been accepted that, before it is rejected, there may need to be evidence or circumstances that displace or cast doubt upon the expert evidence given by a psychiatrist (or psychologist) concerning the appellant’s mental capacity at the material time.[59]
[58] Ramsay v Watson (1961) 108 CLR 642, 645 (Dixon CJ, McTiernan, Kitto, Taylor and Windeyer JJ); Mizzi v The Queen (1960) 105 CLR 659; Kosian v The Queen (2013) 40 VR 335, [55] (Redlich JA, with whom Coghlan JA and Dixon AJA agreed); Question of Law Reserved (No 1 of 2021) (2021) 140 SASR 135, [265] (Livesey JA), albeit in the context of a case concerning self-induced intoxication.
[59] Hone v Western Australia (2007) 179 A Crim R 138, [13] (Steytler P).
In Hone v Western Australia the relevant cases were reviewed by the Court of Appeal in some detail. President Steytler referred, amongst others, to Taylor v The Queen, where the appellant was charged with murder.[60] Expert medical evidence was led at the trial of that case to the effect that the appellant had not been capable, as a result of a disease of the mind, of reasoning whether what he was doing at the time of the killing was wrong according to normally accepted standards. In Taylor v The Queen, Smithers J had explained that where medical opinions were accepted as honest and competent, and were unchallenged, the jury should not reject or ignore those opinions, unless:[61]
… the facts on which the medical witnesses have relied to form their opinions are not satisfactorily established or are contradicted by other acceptable evidence, or the jury are not persuaded that steps of reasoning in the formation of those opinions were soundly taken, or there is some other factor before them reflecting on the validity of the opinions expressed.
[60] Taylor v The Queen (1978) 45 FLR 343.
[61] Taylor v The Queen (1978) 45 FLR 343, 352 (Smithers J).
A similar approach was taken in R v Michaux, another of the cases referred to by Steytler P.[62] In that case a medical practitioner was convicted of administering stupefying drugs and sexually assaulting patients over a couple of years. Whilst the appellant had a mental disease at relevant times, he had initially denied wrongdoing and attacked the complainants’ accounts before engaging in further wrongdoing with other complainants. The Full Court referred to Taylor v The Queen before explaining when it was appropriate to reject unchallenged medical evidence:[63]
… it is otherwise where there is evidence which casts doubt on the medical opinions. Such evidence may go to the factual basis assumed for the purposes of the medical opinions as in R v Wallace [1982] Qd R 265. Again it may be that the behaviour of the prisoner himself is such as to cast such a doubt. Cf Walton v The Queen [1978] AC 788 at 793. And, of course, the jury is amply entitled to scrutinize the medical evidence itself for qualifications, concessions, and reservations. As their Lordships observed in Walton v The Queen … :
It being recognised that the jury on occasion may properly refuse to accept medical evidence, it follows that they must be entitled to consider the quality and weight of that evidence.
[62] R v Michaux [1984] 2 Qd R 159.
[63] R v Michaux [1984] 2 Qd R 159, 164 (Connolly J, with whom Campbell CJ and McPherson J agreed).
The principal judgment in Hone v Western Australia was given by Miller JA (with whom Steytler P and Wheeler JA agreed), who referred to the well-known decision in R v Hall,[64] where Roden J referred to a long line of English cases before explaining:[65]
Juries are not bound to accept and act upon expert evidence. Nevertheless they are not entitled to disregard it capriciously. These two propositions have found expression and support in a line of authorities developed in England with regard to the defences of insanity and diminished responsibility.
[64] Hone v Western Australia (2007) 179 A Crim 138, [123]-[128], [150] (Miller JA, with whom Steytler P and Wheeler JA agreed). R v Hall (1988) 36 A Crim R 368 was relied on by Stanley J in R v Taylor [2014] SASCFC 112.
[65] R v Hall (1988) 36 A Crim R 368, 370-371 (Roden J).
Justice Miller cited with approval the following passage from the reasons of Allen J in R v Hall, which was decided on the common form criminal appeal provision:[66]
There is no rule of law that a verdict of guilty will be quashed as unsafe in any case in which the verdict is inconsistent with medical evidence called for the accused — even where no medical evidence has been called for the Crown. On the other hand there is no rule of law that an appellate court will not quash such a verdict — refusing to do so because it is open to a jury to reject the opinion of any expert witness. Each case is unique. The totality of the evidence must be weighed: Walton [1978] AC 788; 66 Cr App R 25. In assessing medical evidence a multitude of factors must be taken into account — including the standing of the expert, whether he expresses his opinion with conviction or with hedging, whether the opinion expressed in its nature seems reasonable or fanciful, whether it incorporates assumptions not founded upon the evidence given, and whether the evidence given, upon which the opinion is based, is to be believed. It is clearly settled that it can be unreasonable for a jury to reject medical testimony: Walton; Chester [1982] Qd R 252; 5 A Crim R 296.
[66] R v Hall (1988) 36 A Crim R 368, 380-381 (Allen J).
In Hone v Western Australia Miller JA summarised his conclusion in favour of allowing the appeal against the trial judge’s rejection of the psychiatric evidence in the following terms:[67]
Application of these principles to the present case confirms my view that the trial judge ought to have accepted the opinion of Dr Schineanu. He was a well experienced psychiatrist, whose qualifications were not in question. His view was unshaken in cross-examination. His opinion was founded upon evidence as to which there was no relevant challenge (see Hall at 381 (Allen J)). The verdicts which were reached by the trial judge were verdicts which, in my opinion, he could not reasonably have come to.
[67] Hone v Western Australia (2007) 179 A Crim R 138, [126] (Miller JA, with whom Steytler P and Wheeler JA agreed).
Whilst the trier of fact is not bound to accept expert opinion evidence on matters relating to psychiatry or psychology, the rejection of that evidence must not be merely capricious.
Whether a medical or psychiatric opinion is in fact uncontradicted may to some extent be gleaned from any cross-examination of the expert, though that is not decisive, as the cases just mentioned show. Nonetheless, cross-examination may expose difficulties with the facts on which the opinion is founded or some other failing in the opinion and its reasoning. In some cases, the conduct of the accused may provide reason enough to reject the proposition that there was relevant mental incapacity at the time of the offending alleged.
In a case tried by the judge alone it will inevitably be necessary for the judge as the trier of fact to provide adequate reasons for the acceptance or rejection of expert opinion evidence, even if it appears to be uncontradicted.
Appeal ground 3 – there was a denial of procedural fairness
As there is to be a re-trial, it is not necessary to finally rule on whether there was a denial of procedural fairness in this case. That is reinforced by the unsatisfactory way in which the parties addressed the evidence before the court and on which the experts based their opinions. Nonetheless some observations should be made.
The appellant contends that the trial judge rejected the evidence of Professor Young and Ms Heinrich, finding that the opinion of each witness was not of assistance. In reaching this conclusion, the trial judge made numerous criticisms of each expert.
The appellant contends that a number of criticisms were not put to the experts in cross-examination. Two examples illustrate the appellant’s challenge. First, the appellant points to the criticisms made about Professor Young’s approach to researching and expressing views regarding the appellant’s church being “cult‑like”. Secondly, it is said that the trial judge rejected the appellant’s account that he engaged in masturbatory behaviour with other males as he progressed through puberty. To the contrary, the trial judge found that males commenced and stopped engaging in masturbatory behaviour with one another at times inconsistent with the appellant’s account.
A number of other examples were given. It is not necessary to address them all. The appellant contends that, as a result, the trial judge denied him procedural fairness because the expert evidence and his account were subjected to criticisms that he was given no opportunity to answer. The appellant relied on observations made in Re Refugee Review Tribunal; Ex parte Aala, where the denial of procedural fairness was the deprivation of an opportunity to lead evidence and present argument to answer inferences drawn by the Refugee Review Tribunal when concluding that the applicant did not have a well-founded fear of persecution. In that case Gleeson CJ said:[68]
It is possible that, even if the [applicant] had been given an opportunity to deal with the point, the Tribunal's ultimate conclusion would have been the same. But no one can be sure of that. Decisions as to credibility are often based upon matters of impression, and an unfavourable view taken upon an otherwise minor issue may be decisive.
[68] Re Refugee Review Tribunal; Ex parte Aala (2000) 204 CLR 82, [4] (Gleeson CJ). See also Stead v State Government Insurance Commission (1986) 161 CLR 141 where the trial judge made adverse findings on expert evidence where counsel had not been heard on the topic.
The respondent contended that the psychologists relied (almost exclusively) on the account of events and information given by the appellant.[69] The respondent submitted that the appellant was on notice that the evidence of the psychologists was not accepted by the prosecution. The appellant was also on notice that the underlying facts on which they had relied were only as good as the evidence that was elicited, and that the conclusions and opinions of the experts were only as good as that information.
[69] In relation to the diagnosis of ASD, the experts also relied on information provided to them by the appellant’s mother. On some aspects, including their experiences in Zimbabwe, information was given by the appellant’s mother.
The respondent submitted that trials in criminal courts are conducted every day on the basis that the facts are a matter for the trier of fact, and the trier of fact alone.[70] The respondent submitted that the trial judge drew inferences and conclusions on the basis of the evidence, or at times on the basis of a lack of evidence, as well as concerning aspects of the expert opinion being based on a proposition that the trial judge did not find proved. Making findings on that basis, the respondent submitted, did not result in a denial of procedural fairness to the appellant.
[70] R v Baden-Clay (2016) 258 CLR 308, [65] (French CJ, Kiefel, Bell, Keane and Gordon JJ).
At times, the appellant framed the issue as one involving a failure by the prosecution to comply with the so-called rule in Browne v Dunn.[71] That was appropriate. In that case Lord Herschell said:[72]
My Lords, I have always understood that if you intend to impeach a witness you are bound, whilst he is in the box, to give him an opportunity of making any explanation which is open to him; and, as it seems to me, that is not only a rule of professional practice or in the conduct of a case, but is essential to fair play and fair dealing with witnesses …
[71] Browne v Dunn (1893) 6 R 67 HL (Lord Herschell LC).
[72] Browne v Dunn (1893) 6 R 67 HL, 71 (Lord Herschell LC).
His Lordship nonetheless qualified what he had said, emphasising that it may not always be necessary to cross-examine on all issues, at least where prior notice has been given:[73]
Of course I do not deny for a moment that there are cases in which that notice has been so distinctly and unmistakably given, and the point upon which he is impeached, and is to be impeached, is so manifest, that it is not necessary to waste time in putting questions to him upon it.
[73] Browne v Dunn (1893) 6 R 67 HL, 71 (Lord Herschell LC).
The fundamental nature of the principle was pithily described by Wells J in Reid v Kerr in these terms:[74]
It has always seemed to me that if some kind of imputation is to be made against a witness, then, at some stage - ultimately - the precise nature of that imputation should be made clear to the witness so that he is given an opportunity to meet it and, if he can, to explain it or destroy it ... I am well aware that there are more ways of taking a fort than by frontal attack, but I hold it to be a fundamental principle that, when all arts and devices of cross-examination have been exhausted for the purpose of testing whether a particular witness merits adverse criticism, then, at some stage, and in some manner, he should be given the opportunity of meeting the implication and answering it.
[74] Reid v Kerr (1974) 9 SASR 367, 374 (Wells J).
In Burke vCorruption and Crime Commission Buss JA explained the two limbs to the rule:[75]
The rule in Browne v Dunn comprises two limbs. The first limb is that, unless notice has already clearly been given of the party's or cross‑examiner's intention to rely upon such matters, a party or cross‑examiner who intends to invite the court to disbelieve an opposing witness must put to the witness in cross‑examination the grounds upon which the evidence is to be disbelieved. The second limb is that, unless notice has already clearly been given of the party's or cross‑examiner's intention to rely upon such matters, a party or cross‑examiner must put to an opposing witness in cross‑examination the nature of the case upon which it is intended to rely in contradiction of the witness's evidence, especially where that case relies upon inferences to be drawn from other evidence.[76]
[75] Burke v Corruption and Crime Commission (2012) 289 ALR 150, [180] (Buss JA, with whom Martin CJ and Mazza JA agreed).
[76] See Allied Pastoral Holdings Pty Ltd v Federal Commissioner of Taxation [1983] 1 NSWLR 1; (1983) 70 FLR 447, 16, 18, 26 (Hunt J); Village Cay Marina Ltd v Acland [1998] BCC 417, 426 (Lord Hoffmann, Lord Lloyd of Berwick, Lord Nolan, Lord Hope of Craighead and Sir Andrew Legatt agreeing); Williams v Dawson (2000) 31 MVR 559, [32] (Parker J, Kennedy and Wheeler JJ agreeing); Merrey v The State of Western Australia [2010] WASCA 62, [9]-[11] (McLure P, Owen JA and Jenkins J agreeing); Bale v Mills (2011) 81 NSWLR 498, [42]-[48] (Allsop P, Giles JA and Tobias AJA).
Justice Buss went on to emphasise that the policy rationale underpinning the rule in Browne v Dunn is the securing of fairness in the conduct of adversarial proceedings.[77] As his Honour explained, the first limb is concerned with achieving fairness to witnesses and a fair trial between the parties. The second limb is concerned with the weight or cogency of evidence.[78] Moreover, the rule is not absolute and it must be applied flexibly, as Gleeson CJ explained in R v Birks:[79]
It is plain that their Lordships [in Browne v Dunn], whilst recognising and affirming a rule of practice in the terms in which they expressed themselves, also recognised the need for flexibility in its application. That need arises from the very nature of the subject matter which it concerns. The central purpose of the rule is to secure fairness in the conduct of adversary proceedings. That consideration provides the best guide, both to the practical requirements of the rule in a given case, and to the consequences which may properly flow from its non‑observance, including the remedies that are available to deal with a problem so created.
[77] Burke v Corruption and Crime Commission (2012) 289 ALR 150, [181] (Buss JA, with whom Martin CJ and Mazza JA agreed). See R v Birks (1990) 19 NSWLR 677, 688 (Gleeson CJ, McInerney JJ agreeing); Adamson v Ede [2009] NSWCA 379, [56] ‑ [62] (Campbell JA, Giles and Hodgson JJA agreeing); Chanaa v Zarour [2011] NSWCA 199, [13] (Campbell JA, Bathurst CJ and Tobias AJA agreeing).
[78] See Bulstrode v Trimble [1970] VR 840, 846-848 (Newton J); Allied Pastoral Holdings Pty Ltd v Federal Commissioner of Taxation [1983] 1 NSWLR 1, 18 (Hunt J).
[79] R v Birks (1990) 19 NSWLR 677, 688 (Gleeson CJ, with whom McInerney JJ agreed).
Ultimately, the rule in Browne v Dunn may be seen as adjunct to procedural fairness. Procedural fairness is an essential attribute of a court’s processes.[80] In the criminal court, procedural fairness may be conceptualised as according the accused a fair trial.[81] Whilst “descriptively accurate”,[82] whether an accused has been afforded procedural fairness requires a careful analysis of what is required in the particular case. That is to say, the “rules of procedural fairness do not have immutably fixed content.”[83] At their core, they require that the person affected know of the critical issues to be addressed, and of any significant, credible material which is adverse to the affected person.[84] It is not ordinarily necessary to put to a party any matter which is in any event clearly in issue.[85]
[80] Assistant Commissioner Condon v Pompano Pty Ltd (2013) 252 CLR 38, [156] (Hayne, Crennan, Kiefel, Bell JJ), [194] (Gageler J).
[81]New South Wales v Canellis (1994) 181 CLR 309, 329 (Mason CJ, Dawson, Toohey, McHugh JJ).
[82] Assistant Commissioner Condon v Pompano Pty Ltd (2013) 252 CLR 38, [156] (Hayne, Crennan, Kiefel and Bell).
[83] Assistant Commissioner Condon v Pompano Pty Ltd (2013) 252 CLR 38, [156] (Hayne, Crennan, Kiefel and Bell).
[84] Kioa v West (1985) 159 CLR 550, 587 (Mason J), 629 (Brennan J).
[85] See Stern v National Australia Bank Ltd (2000) 171 ALR 192, [42] (Hill, O'Connor and Moore JJ).
The necessity to afford procedural fairness in the conduct of a proceeding extends to when it is appropriate for the judge to make findings on matters which have not been exposed by the evidence or put to the witnesses for their response.[86]
[86] Macks v Viscariello (2017) 130 SASR 1, [459]-[492] (Lovell J, Corboy and Slattery AJJ).
In this context, Kuhl is an example of a case addressing the consequences of a failure to afford procedural fairness in a manner akin to a failure to comply with Browne v Dunn.[87] In the course of an action for injuries sustained in an industrial accident, the trial judge found that the plaintiff was “less than expansive” when describing how the accident happened, stating that he had “formed the view that for whatever reason he [the plaintiff] was reluctant to say precisely what happened”.[88] To support that view, the trial judge set out four questions and the answers given by the plaintiff during his evidence in chief. The plaintiff was not cross-examined on how the accident happened. The trial judge asked no questions. Counsel for the defendant did not make a submission on the issue in closing address. In the High Court, Heydon, Crennan and Bell JJ held that the conclusion that the plaintiff was reluctant to say what had happened amounted to a finding that he had deliberately failed to comply with his duty to tell the whole truth.[89] As defence counsel had not cross-examined on this issue it was not open to put that submission in closing. The majority questioned how, in those circumstances, it could have been open to the trial judge, without warning, to incorporate this finding into his reasons for judgment.[90] The majority stated:[91]
There was no point in the trial judge mentioning his conclusion that the plaintiff’s evidence was not frank and complete unless it played a role in his decision adverse to the plaintiff. In the absence of any challenge from the cross-examiner to the frankness and completeness of the plaintiff’s evidence, it was incumbent on the trial judge, if his conclusion that the plaintiff had not been frank and complete was to play a role in his decision adverse to the plaintiff, to make the challenge himself. Perhaps the criticism in the judgement did not occur to the trial judge until after the plaintiff had left the box, or until after the hearing had concluded and before the Judge’s reserved judgement was given. It remained necessary either to recall the plaintiff or to have no regard to that aspect of the plaintiff’s evidence.
[87] Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361 (Kuhl).
[88] Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361, [60] (Heydon, Crennan and Bell JJ).
[89] Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361, [62] (Heydon, Crennan and Bell JJ).
[90] Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361, [72] (Heydon, Crennan and Bell JJ).
[91] Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361, [75] (Heydon, Crennan and Bell JJ).

Accordingly, it was an error to make a finding without providing the affected party with the opportunity to deal with the subject matter of the finding.
Bale v Mills is a similar case.[92] A former client sued a firm of solicitors, alleging a failure to properly advise in connection with a work injury claim settlement. The solicitor handling the settlement gave evidence. An issue at the trial was a calculation made by the solicitor of the “preclusion period”, the period of time before the client could again access Centrelink payments. It was alleged that the solicitor’s calculation was wrong. A letter from Centrelink which disclosed the error was tendered. It was proved that the letter was received by the solicitor before he wrote to his client. The solicitor did not tell his client about the error or the letter.
[92] Bale v Mills (2011) 81 NSWLR 498.
In final address it was submitted that the solicitor deliberately misled his client so as to conceal his error. Though that allegation had not been put in cross‑examination, the trial judge accepted it.
On appeal, it was conceded that counsel should not have made that submission. The Court of Appeal found that the concession was properly made, adding that it ought not to have been accepted by the judge.[93] The Court accepted, on the authority of Kuhl, that the rule in Browne v Dunn, being essentially one of fairness, applied equally and independently to the trial judge and to counsel.[94] In that case the Court rejected the proposition that reliance on the rule had been waived by an absence of objection.[95]
[93] Bale v Mills (2011) 81 NSWLR 498, [41] (Allsop P, Giles JA and Tobias AJA).
[94] Bale v Mills (2011) 81 NSWLR 498, [64] (Allsop P, Giles JA and Tobias AJA), “It was contended by the appellants on the authority of Kuhl that the rule in Browne v Dunn , being one of fairness, applied equally (and presumably, independently) to a trial judge as to counsel. This is no doubt so…”.
[95] Bale v Mills (2011) 81 NSWLR 498, [64]-[68] (Allsop P, Giles JA and Tobias AJA).
The issues in this case were clear and circumscribed by the statutory requirements of Part 8A of the CLCA, the parties’ openings and the expert opinion evidence which had been served. The proceedings conducted under Part 8A of the CLCA are broadly, though not entirely, adversarial.
Forensic decisions had to be made in that context. In this case the appellant bore the burden of proof in a case where the issues had been narrowed, at least to some extent, by the expert opinion evidence and the criticisms made during the cross-examination of it. There was no obligation on either party, or the trial judge, to forecast every one of the failings in the evidence of the other party, particularly the party bearing the burden of proof.
Where the issues in contest are exposed, and the burden of proof is clear, it is simply for each party to persuade the court as that party sees fit. Whilst both parties failed to adhere to proper practice and clearly identify their approach to the admission of evidence, as earlier indicated, the prosecution as respondent to the application was not required to forecast what it suggested was defective reasoning in the opinions of the appellant’s experts ahead of cross-examination or final address. There was no failure to comply with the rule in Browne v Dunn.
There was no free-standing obligation in the trial judge as decision-maker to forecast or disclose the mental processes or lines of reasoning that might be undertaken. In F Hoffmann-La Roche & Co AG v Secretary of State for Trade and Industry, Lord Diplock explained:[96]
… the rules of natural justice do not require the decision maker to disclose what he is minded to decide so that the parties may have a further opportunity of criticising his mental processes before he reaches a final decision. If this were a rule of natural justice only the most talkative of judges would satisfy it and trial by jury would have to be abolished.
[96] F Hoffmann-La Roche & Co AG v Secretary of State for Trade and Industry [1975] AC 295, 369. The High Court has endorsed Lord Diplock’s reasoning: SZBEL v Minister for Immigration and Multicultural and Indigenous Affairs (2006) 228 CLR 152, [48] (Gleeson CJ, Kirby, Hayne, Callinan and Heydon JJ).
Implicit in Lord Diplock’s observations is the proposition that the proposed “mental processes” of a trier of fact will not usually be revealed, and this works no denial of procedural fairness. Fairness does not necessarily require that a judicial officer forewarn a party about all possible reasons for failure.[97]
[97] Re Minister for Immigration and Multicultural Affairs and Another; Ex Parte Miah (2001) 206 CLR 57, [31] (Gleeson CJ and Hayne J).
Having said that, it is necessary that a trial judge articulate any key criticisms of expert opinion evidence, at least where they are not obvious or have not already been articulated by the opposing party in cross-examination. Whilst that will usually be done in final address,[98] it may need to be done before cross-examination is concluded.[99]
[98] Stead v State Government Insurance Commission (1986) 161 CLR 141.
[99] Kuhl v Zurich Financial Services Australia Ltd (2011) 243 CLR 361; Bale v Mills (2011) 81 NSWLR 498, [64] (Allsop P, Giles JA and Tobias AJA); Macks v Viscariello (2017) 130 SASR 1, [459]-[492] (Lovell J, Corboy and Slattery AJJ).
In this case the overarching difficulty remained the misunderstandings between the parties about the evidence before the court and the basis upon which the expert’s opinions were or were not supported by it. Many of the appellant’s criticisms can be traced back to that core difficulty.
Appeal ground 4 – the trial judge’s reasons were inadequate
Again, it is not necessary to finally rule on this ground.
It is not necessary to repeat the observations earlier made about the uncertain factual basis upon which this matter proceeded. In a broad sense, it may be accepted that, though this difficulty was the product of the conduct of the matter by the parties, it necessarily led to some uncertainty as well as inadequacy in the reasoning about the basis upon which the expert opinion evidence was rejected in this case.
To return to an issue adverted to earlier, it is clear that the trial judge formed a number of unfavourable views about the expert opinion evidence, and concluded that it did not assist him. However, it remains unclear whether the ultimate rejection of that evidence was based on the suggested failure of the experts to address deficiencies in the histories they were given, or deficiencies in the reasoning they employed, or simply because the trial judge thought that their opinions were wrong.
To that extent at least, the reasons were inadequate.[100]
[100] R v Keyte (2000) 78 SASR 68 (Doyle CJ); Douglass v The Queen (2012) 86 ALJR 1086.
Conclusion
For these reasons, the mental competence investigation miscarried.
In consequence, there must be a new trial.