The defence of mental health impairment and/or cognitive impairment, formerly the defence of mental illness, is provided in the Mental Health and Cognitive Impairment Forensic Provisions Act 2020 (“the Act”) which commenced on 27 March 2021 and replaced the Mental Health (Forensic Provisions) Act 1990 (“the 1990 Act”).

For fitness to be tried, which is dealt with in Pt 4 of the Act, see [4-300] Procedures for fitness to be tried (including special hearings) which includes some general observations about some of the terms and concepts in the Act.

For the partial defence to murder of what used to be termed “substantial impairment by abnormality of mind” in s 23A of the Crimes Act 1900, see [6-550] Substantial impairment by mental health impairment or cognitive impairment.

The present chapter is concerned with the provisions of Pt 3 of the Act and what used to be referred to as the defence of mental illness and the special verdict of “not guilty by reason of mental illness” in Pt 4 of the 1990 Act. If the defence of mental health impairment and/or cognitive impairment in s 28 of the Act is established the special verdict that must be returned is “act proven but not criminally responsible”: s 30.

The Attorney General, the Hon Mark Speakman, said in the Second Reading Speech for the Mental Health and Cognitive Impairment Forensic Provisions Bill 2020 that Pt 3 updated and legislated what was the common law test for the defence of mental illness and rewrote the special verdict. The defence provided in what became s 28 was said to “closely mirror” the common law M’Naghten’s test “but with updated terms”: NSW, Legislative Assembly, Debates, 3 June 2020, p 2351. Consequently, authorities concerned with the mental illness defence at common law, for example, R v Porter (1933) 55 CLR 182, have continued relevance.

See generally, Criminal Practice and Procedure NSW at [17-s 28]–[17-s 34] and accompanying annotations; Criminal Law NSW at [MHCI.28.20]–[MHCI.28.240]. See also “Introducing the new Mental Health and Cognitive Impairment Forensic Provisions Act 2020”, The Hon Justice Mark Ierace, (2021) 33(2) JOB 15 and “Clinical issues with the Mental Health and Cognitive Impairment Forensic Provisions Act 2020”, Dr Kerri Eagle and Anina Johnson, (2021) 33(7) JOB 67.

Savings and transitional provisions are made in Sch 2 of the Act, including the extent to which the Act may apply to existing proceedings. Clause 5 provides that if a question has been raised prior to the commencement of the Act as to whether the accused was mentally ill at the time of commission of the offence, the 1990 Act continues to apply until a determination is made as to whether a special verdict should be entered (or the defence is no longer being raised). If it is determined that the special verdict of not guilty by reason of mental illness would have been found, the court must instead find the special verdict of act proven but not criminally responsible. This is what occurred in Masters v R [2022] NSWCCA 228.

While it is theoretically necessary for the Crown to prove beyond reasonable doubt that the act (or omission) constituting the offence was a voluntary one, that is a matter that is presumed unless the accused discharges an evidentiary onus to indicate otherwise. If the issue is raised on the evidence it is then necessary for the Crown to prove beyond reasonable doubt that the act was a voluntary act of the accused: The Queen v Falconer (1990) 171 CLR 30 at 56, 63, 77. See [4-350] Voluntary act of the accused and [6-050] Automatism — sane and insane.

Where no issue is raised as to the voluntariness of the accused’s act, it is only necessary for the Crown to prove the physical elements of the alleged crime before the impairment defence falls for determination. That is, consideration of whether the mental element has been proved is only necessary if it is determined that the defence has failed: R v Tonga [2021] NSWSC 1064 at [15]; R v Siemek (No 1) [2021] NSWSC 1292 at [16]; R v Jawid [2022] NSWSC 788 at [97]–[98]. The proposition is traced to Hawkins v The Queen (1994) 179 CLR 500 at 512–517 and R v Minani (2005) 63 NSWLR 490 at [32]–[33]. In R v Jawid at [99]–[106], Davies J provided reasons for concluding that the issue of criminal responsibility must be considered before any question of substantial impairment.

It was held in Hawkins v The Queen at 512–513, 517 that medical evidence going to a defence of mental illness cannot be taken into account in determining whether an act is voluntary but may be taken into account in determining whether the act was done with a specific intent. Having regard to the rationale for this as explained by the High Court (at 513), this would appear to apply to both the mental health and the cognitive impairment defences.

Section 28 of the Act provides for a “defence” of mental health impairment, cognitive impairment “or both”.

While it is commonly referred to as a “defence”, it is not something that may only be raised by the accused. There are cases in which the Crown has contended the special verdict should be returned whereas the accused contended there should be an acquittal as a result of sane automatism (absence of voluntariness) or in a murder trial there should be a verdict of guilty of manslaughter by reason of substantial impairment because of mental health or cognitive impairment. The former was the case in R v DB [2022] NSWCCA 87 and the latter was the case in R v Jawid [2022] NSWSC 788. In R v Jawid, Davies J applied R v Ayoub [1984] 2 NSWLR 511 and s 28(2) of the Act in holding that the Crown is entitled to raise the issue of criminal responsibility by contending that the accused has a mental health impairment and that despite s 141 of the Evidence Act 1995, the standard of proof is on the balance of probabilities.

As to the reference in s 28(1) to “or both”, in their article referred to above, Eagle and Johnson observe (at 68) that mental health impairments and cognitive impairments may overlap clinically and diagnostically and the reference in s 28 (and in the test for fitness in s 36) to both “avoids the need for clinicians and courts to make potentially artificial determination as to which disorder is contributing to the relevant impairment”.

The terms, “mental health impairment” and “cognitive impairment” are defined in ss 4 and 5 of the Act respectively (and in identical terms in ss 4C and 23A of the Crimes Act). The definitions of mental health impairment and cognitive impairment each have three limbs set out conjunctively in s 4(1)(a)–(c) and s 5(1)(a)–(c).

The three subsections of s 4 comprise in subs (1) a definition of what is a mental health impairment; in subs (2) a non-exhaustive list of disorders from which a mental health impairment may arise; and in subs (3) an exclusion of two matters from solely giving rise to a mental health impairment (the temporary effect of ingesting a substance and a substance use disorder). Section 5 follows a similar structure in subss (1) and (2) but with terms and concepts relevant to cognitive impairment and without the exclusion of the temporary effect of ingesting a substance, or a substance use disorder.

It was held by a majority in R v DB at [43] that under the common law, the acts of a person who is asleep and engaging in somnambulistic activity are not willed acts. The accused was not legally responsible for them and would be entitled to an outright acquittal. It was further held (at [64]) that the Act did not alter this position in that there was no mental health impairment as defined in s 4: there was no disturbance of volition within s 4(1)(a) and the lack of volition while asleep was of no clinical significance for the purposes of s 4(1)(b).

It has been held in two single judge decisions that the onus of proof of the exclusion in s 4(3) is upon the Crown: R v Miller [2022] NSWSC 802 at [53]–[62] and R v Sheridan [2022] NSWSC 1669 at [20]–[26]. In the latter, the court rejected a proposition that the onus was upon the Crown to prove the matter beyond reasonable doubt and held that the standard of proof on the Crown was on the balance of probabilities. These matters appear to involve issues that were not considered and neither have the judgments been the subject of appellate review.

In R v Miller at [50]–[51], Cavanagh J held that an impairment by way of a substance induced disorder which existed at the time of the event which was temporary in nature, and which was caused solely by the ingestion of drugs without any underlying cause would be within the possible operation of s 4(3). He was not satisfied that the exception in s 4(3) could only apply where the accused was intoxicated by drugs at the time of committing the act or could never apply if s 4(2) is satisfied.

There are two limbs to the defence set out in s 28(1): R v Siemek (No 1) [2021] NSWSC 1292 at [84]–[86]. First, whether at the time of carrying out the act constituting the offence the accused had a mental health and/or cognitive impairment. Second, whether such impairment(s) had the effect that the accused did not know the nature and quality of the act or did not know that the act was wrong (that is, could not reason with a moderate degree of sense and composure about whether the act, as perceived by reasonable people, was wrong). It is presumed that the accused did not have either such impairment until the contrary is proved, with such proof being on the balance of probabilities: s 28(2)–(3). Whether the accused did not know the nature and quality of the act involves an assessment of whether the accused knew the physical nature of what he/she was doing or the implications of it: The King v Porter (1933) 55 CLR 182 at 188; Willgoss v The Queen (1960) 105 CLR 295 at 300.

The definition within s 28(1)(b) of not knowing that the act was wrong meaning that the accused “could not reason with a moderate degree of sense and composure about whether the act, as perceived by reasonable people, was wrong” adopts the formulation of Dixon J in The King v Porter at 189–190 which included his Honour saying that “wrong” meant “wrong having regard to the everyday standards of reasonable people”. It was confirmed in Stapleton v The Queen (1952) 86 CLR 358 at 375 that the issue is whether the accused was able to reason as to what is right and wrong according to the ordinary standards adopted by reasonable people as opposed to knowing that the act was contrary to and punishable by law.

There was no legal requirement to adduce medical evidence to prove the former defence of mental illness: Lucas v The Queen (1970) 120 CLR 171 at 174. However, it was observed in Tumanako v R (1992) 64 A Crim R 149 at 160 that there may be a practical necessity to do so and Johnson J noted in R v Siemek (No 1) [2021] NSWSC 1292 at [92] that it may be more than a practical necessity to have expert medical evidence for that part of the definition of a mental health impairment that a disturbance of thought, mood, volition, perception or memory “would be regarded as significant for clinical diagnostic purposes”. The same is likely the case about aspects of the definition of cognitive impairment. Juries (and judges sitting alone) are not bound to accept and act upon expert evidence but must not disregard it capriciously: R v Hall (1988) 36 A Crim R 368; Goodridge v R [2014] NSWCCA 37 at [116]. Unanimous medical evidence ought not be rejected unless there is evidence which can cast doubt upon it: R v Tumanako at 160–161; Da-Pra v R [2014] NSWCCA 211 at [337].

Section 29 provides that the judge must explain the matters listed in paragraphs (a) to (e) to the jury. They are the findings which may be made on the trial and their legal and practical consequences: s 29(a)–(b). Section 29(d) adds this includes that if the special verdict is returned, the accused may be ordered to be released by the Mental Health Review Tribunal only if the Tribunal is satisfied the safety of the accused and members of the public will not be seriously endangered. Section 29(c) provides the jury is to be informed about the composition of the Mental Health Review Tribunal and its functions in respect to forensic patients. Paragraph (e) provides the jury be told that it should not be influenced in the return of a verdict by the consequences of a special verdict. The provision of such instruction to a jury appears to have derived from R v Hilder (1997) 97 A Crim R 70 at 81. The Attorney General indicated in his Second Reading Speech stakeholders had asked that this requirement be retained so that a jury is not deterred from returning a special verdict out of concern about indeterminate detention: NSW, Legislative Assembly, Debates, 3 June 2020, at 2352.

The Mental Health Review Tribunal is constituted under Ch 6 of the Mental Health Act 2007 (provisions relating to membership of the Tribunal are found in Sch 5.) The functions of the Tribunal in relation to forensic patients who have been the subject of a verdict of act proven but not criminally responsible are contained in Pt 5 of the Act. Information included in the suggested direction at [6-280] for compliance with s 29 of the Act has been drawn from these sources.

Section 31 of the Act provides for a streamlined procedure enabling a court to enter a special verdict at any time in the proceedings, even before a jury is empanelled. It is necessary that the defendant is legally represented and that the parties agree that the proposed evidence establishes the defence in s 28. If the court is satisfied the defence is established the special verdict may be entered. There is no requirement that a trial be convened, that the defendant elect to be tried by judge alone, or that the judge comply with the requirements for such a trial under ss 132 and 133 of the Criminal Procedure Act 1986. It remains necessary for a judge to provide reasons for the outcome as a necessary function of judicial proceedings. See R v Sands [2021] NSWSC 1325 at [3]–[4]; R v Jackson [2021] NSWSC 1404 at [7]–[13].

If the defence of mental health or cognitive impairment has been established, the jury must return the special verdict of act proven but not criminally responsible: s 30. Section 32 provides that if the special verdict is entered, there is no requirement for the special verdict to be entered also in respect of an offence available as an alternative.

The orders a court may make upon the return of a special verdict are set out in s 33(1). They include an order for the unconditional or conditional release of the person from custody but before making such an order the court must be satisfied that the safety of the person or any member of the public will not be seriously endangered: s 33(3).

The court may request a report by a forensic psychiatrist, or a person of a class prescribed by the regulations as to the condition of the person and whether their release is likely to seriously endanger the safety of themself or any member of the public: s 33(2). Clause 4 of the Mental Health and Cognitive Impairment Forensic Provisions Regulation 2021 prescribes for the purposes of s 33(2) a person who is a registered psychologist who has, in the opinion of the court, appropriate experience or training in forensic psychology or neuro-psychology. Section 30L of the Crimes (Sentencing Procedure) Act 1999 enables a victim impact statement to be provided to the court following the return of a special verdict at a trial or special hearing (and a verdict at a special hearing that on the limited evidence available an accused person committed an offence). This has been described as a “significant” and “important” reform: R v Siemek (No 2) [2021] NSWSC 1293 at [3], [6]–[7]. Any victim impact statement must be provided to the Mental Health Review Tribunal: s 30N(3). Section 30M provides that a court may seek submissions by the “designated carer or principal care provider” (as defined in the Mental Health Act 2007) of an accused person after the return of such a verdict. It is suggested that an inquiry be made as to whether any of these provisions should be applied before the court finalises a matter by making orders pursuant to s 33 of the Act. There must be a referral of the person to the Mental Health Review Tribunal if a special verdict is returned unless an order is made for the person’s unconditional release: s 34.

It is recommended that the jury be assisted by the provision of a document setting out the elements of the offence the Crown is required to prove together with the elements of the defence raised. A document setting out the composition and relevant functions of the Mental Health Review Tribunal in respect to forensic patients may also assist.

The suggested direction assumes the jury have been directed as to all of the elements of the offence the Crown is required to prove. It is based upon the more commonly encountered case in which there is no dispute that the accused committed the physical act constituting the offence and that the defence raised is one of mental health rather than cognitive impairment. The direction may be readily adapted if the case at hand is otherwise. A suggested substitution of an explanation of “cognitive impairment” to use in lieu of “mental health impairment” appears below.

If there is an issue as to whether the accused’s act was voluntary, the following direction should be preceded by a direction as to that, see [4-350] Voluntary act of the accused. If an issue of automatism arises as the basis of an assertion of involuntariness, see also [6-050] Automatism — sane and insane.

The suggested direction for mental health impairment may be readily adapted for a case involving an issue of cognitive impairment (or both). The following is suggested for substitution of that part of the direction concerned with the nature of the impairment.