When does a trial irregularity become a miscarriage of justice? The impact of the recent High Court of Australia decision of Brawn v The King [2025] HCA 20.

Our thanks to barrister Susan Hedge for her assistance in interpreting the meaning and impact of this decision in what is a highly complex and specialised area of law.

On 7 May 2025, the High Court of Australia handed down the decision of Brawn v The King [2025] HCA 20. Important for all criminal lawyers with an appellate practice, the Court, in a unanimous decision, confirmed that there is a materiality threshold (albeit a relatively low one) that must be met before a miscarriage of justice is substantial enough for a matter to be appealed.

Legal context

All Australian states and territories enable a person convicted of an offence to appeal their conviction.  In Queensland, for instance, section 668E of the Criminal Code Act 1899 states that, where there has been a miscarriage of justice in a criminal trial, the matter can be appealed to the Queensland Court of Appeal. Importantly, however, this is subject to the proviso that the court may dismiss an appeal if it considers that no substantial miscarriage of justice has occurred.

The interpretation of this section and corresponding sections in other states has been a point of contention across several High Court decisions.

For instance, in the High Court appeal of MDP v The King (awaiting final decision) the appellant submitted that there should be no materiality threshold, drawing on the approach of Edelman J in HCF v The Queen (2023) 97 ALJR 978. In Huxley v The Queen [2023] HCA 40, it has been proposed that the level of the threshold varies depending on the nature of the error that had been made.  The cases of Hofer v The Queen (2021) 274 CLR 35, Edwards v The Queen (2021) 273 CLR 585 and HCF v The Queen are authorities for the proposition that there is a materiality threshold required for miscarriage of justice appeals.

Brawn harmonises and clarifies the extent of the threshold, and how it is to be applied.

Factual background

The appellant in Brawn was convicted of maintaining an unlawful sexual relationship with a child under the age of 17 years. The key issue at trial was whether the perpetrator was the appellant, or another member of the complainant’s community. The complainant had told police that her ‘uncle’ committed the offences, but referred to multiple members of her community, including her father, as her ‘uncle’.

The appellant’s father had also been charged with committing unlawful sexual acts against a teenage girl during a period that overlapped with the charge period for the appellant. The prosecution did not disclose this information to the appellant until after the appellant’s trial had concluded.

The matter was appealed to the South Australian Court of Appeal on the ground that the prosecution had breached their duty of disclosure by failing to disclose the information about the appellant’s father’s criminal charges. The appellant submitted that the undisclosed material may have assisted in their cross-examination of witnesses regarding the identity of the perpetrator and accordingly, the failure to disclose amounted to a miscarriage of justice.

South Australian Court of Appeal

The South Australian Court of Appeal agreed that the prosecution had breached their duty of disclosure. However, the error did not cause a substantial miscarriage of justice because the appellant did not demonstrate that, had the disclosure been made, the appellant’s defence would have been conducted differently.

High Court Decision

In a unanimous decision, the High Court found that, where there has been an error or irregularity in a criminal trial, it must be shown that the error or irregularity could have affected the course of the trial or the reasoning of the jury in reaching their verdict. The South Australian Court of Appeal therefore erred by requiring the appellant to demonstrate that, had the error not been made, the trial would have been conducted differently.

Arguably, the emphasis on “could have affected…the course of the trial or the reasoning of the jury” is a lower threshold than previous formulations.  Here, the emphasis is on an irregularity which could have affected how the trial was conducted or how the jury was directed. An appellant need not show that the irregularity would have changed the outcome.  In Brawn’s case, the defence would not have had a proper basis to suggest that the appellant’s father may have been the perpetrator without the material that the prosecution failed to disclose. This denied them the opportunity to run the trial in a way that could have realistically affected the reasoning of the jury. The appellant was not required to prove that the jury would have otherwise reached a different decision.