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Supreme Court 3 March 2026

R v Jensen

[2026] NSWSC 140

Homicide

Citation: R v Jensen [2026] NSWSC 140
Court: Supreme Court of New South Wales
Date: 3 March 2026
Judge(s): Boulten J

Background

The accused was charged with the murder of a woman at her apartment in Merrylands, NSW, on 9 April 2023. The accused had attacked the deceased with a bladed weapon, causing her death. The physical acts constituting the offence were not in dispute between the parties.

The accused pleaded not guilty and advanced a defence of mental health impairment under s 28 of the Mental Health and Cognitive Impairment Forensic Provisions Act 2020 (NSW) ("the Forensic Provisions Act"). The trial proceeded as a judge-alone trial, with Hamill J having made orders under s 132 of the Criminal Procedure Act 1986 (NSW) on 5 September 2025 following consent from the Crown. The overwhelming majority of the evidence and submissions at trial were directed to the mental health impairment defence.

The central question was whether the accused, at the time of the killing, had a mental health impairment within the meaning of the Forensic Provisions Act that rendered him not criminally responsible — specifically, whether he did not know that his act was wrong. The Crown contended that any impairment was caused solely by one of the excluded matters under s 4(3) of the Act (that is, the temporary effect of ingesting a substance or a substance use disorder), which would preclude the defence.

  • Whether the accused had a "mental health impairment" within the meaning of s 4(1) of the Forensic Provisions Act at the time of the killing — that is, whether he had a clinically significant disturbance of thought, mood, volition, perception or memory that impaired his emotional wellbeing, judgment or behaviour.

  • Whether the Crown could establish, on the balance of probabilities, that the accused's impairment was caused solely by either the temporary effect of ingesting a substance or a substance use disorder, thereby excluding the defence under s 4(3).

  • Whether the mental health impairment had the effect that the accused did not know the nature and quality of his act, or did not know that the act was wrong (i.e., could not reason with a moderate degree of sense and composure about whether the act, as perceived by reasonable people, was wrong).

  • The elements of murder under s 18 of the Crimes Act 1900 (NSW), including whether the accused performed a voluntary act causing death and did so with the requisite mental state.

Decision

Boulten J found that the Crown had established beyond reasonable doubt that the accused committed the physical act constituting the offence. It was accepted by both parties that the accused attacked the deceased with a bladed weapon at her Merrylands apartment, causing her death. There was no real dispute on the first element of murder.

The critical contest was over the mental health impairment defence. The accused bore the onus of proving this defence on the balance of probabilities — a lower standard than the criminal standard of beyond reasonable doubt — while the Crown bore the onus of proving, also on the balance of probabilities, that any impairment was caused solely by an excluded matter under s 4(3). His Honour applied the directions endorsed by the Court of Criminal Appeal in Delaney v The King [2025] NSWCCA 76, which adopted the framework articulated by Dhanji J in R v Patterson (No 6) [2024] NSWSC 458. This framework sets out a three-stage inquiry: first, whether the accused had an impairment satisfying s 4(1); second, whether the Crown could establish a s 4(3) exclusion; and third, whether the impairment had the relevant effect on the accused's knowledge.

Boulten J ultimately concluded that the accused had established the defence of mental health impairment. The act was proved, but the accused was not criminally responsible. His Honour determined that the special verdict of "act proven but not criminally responsible" was the appropriate finding. In reaching this conclusion, Boulten J emphasised that the accused's fatal actions were tragic and devastating for the deceased's family and friends, but that the legal requirements of the defence had been met.

As required by s 29 of the Forensic Provisions Act, the judgment set out the legal and practical consequences of the special verdict, including that the accused would be subject to review by the Mental Health Review Tribunal, could be detained in a secure facility, and would not be released unless the Tribunal was satisfied that neither the accused nor any member of the public would be seriously endangered.

Orders Made

  • Special verdict of "act proven but not criminally responsible" entered in respect of the charge of murder.

  • The accused's case was to be referred to the Mental Health Review Tribunal for ongoing review and determination of detention or conditional release arrangements (as outlined under the Forensic Provisions Act framework described in the judgment).

Note: The full text of the judgment was truncated; the precise dispositional orders regarding detention or release conditions may have been addressed in the portion of the judgment not available for this summary.

Key Takeaways

  • The burden framework under ss 4 and 28 of the Forensic Provisions Act is now well settled. The Supreme Court confirmed that the accused bears the onus of establishing mental health impairment on the balance of probabilities, while the Crown must prove, also on the balance of probabilities, that any impairment was caused solely by an excluded matter under s 4(3). Boulten J adopted the Patterson (No 6) and Delaney directions as the preferred formulation of this framework.

  • Under s 4(3), the word "solely" carries significant weight. Where other contributing causes existed, such as an underlying psychotic disorder, the exclusion did not apply even if substance use played a role. The Crown was required to demonstrate that the impairment was caused exclusively by the temporary effect of ingesting a substance or by a substance use disorder.

  • Compliance with s 29 of the Forensic Provisions Act required the Court to publicly articulate the explanations ordinarily given to a jury. In this judge-alone trial, Boulten J set out those explanations (including the consequences of a special verdict) to ensure transparency and maintain public confidence in the process.

  • A special verdict of not guilty by reason of mental health impairment does not result in the accused's release. The judgment detailed the oversight mechanism under which the accused becomes subject to the jurisdiction of the Mental Health Review Tribunal and may be detained in a prison, hospital, or other facility until the Tribunal is satisfied that release would not seriously endanger the public or the accused.

  • This decision contributes to a growing body of Supreme Court authority (including R v Mavin, R v Miller, R v Sheridan, R v Murray, and R v Patterson (No 6)) providing guidance on the practical application of the mental health impairment defence under the 2020 Act.

Legislation and Cases Referenced

Legislation:
- Crimes Act 1900 (NSW), ss 18, 23A
- Criminal Procedure Act 1986 (NSW), ss 132, 133
- Mental Health and Cognitive Impairment Forensic Provisions Act 2020 (NSW), ss 4, 28, 29

Cases:
- Da-Pra v The Queen [2014] NSWCCA 211
- Delaney v The King [2025] NSWCCA 76
- Fleming v The Queen (1998) 197 CLR 250; [1999] HCA 68
- Hawkins v The Queen (1994) 179 CLR 500; [1994] HCA 28
- R v Hall (1988) 36 A Crim R 368
- R v Klamo (2008) 18 VR 644; [2008] VSCA 75
- R v Mavin [2023] NSWSC 455
- R v Miller [2022] NSWSC 802
- R v Murray [2024] NSWSC 503
- R v Patterson (No 6) [2024] NSWSC 458
- R v Sheridan [2022] NSWSC 1669
- R v Tumanako (1992) 64 A Crim R 149
- Stapleton v The Queen (1952) 86 CLR 358; [1952] HCA 56
- The King v Porter (1933) 55 CLR 182; [1