The framework of criminal defences 

Once an offence appears to be made out on its physical and fault elements, the analysis is not finished. The accused may still escape liability by raising a defence, but "defence" is used loosely in everyday speech to cover two conceptually different moves, and keeping them separate is essential to a well-structured answer.

Denial versus true defence

The first kind of "defence" is not a defence at all in the strict sense — it is a denial of an element. If an accused argues they did not perform the conduct, did not cause the result, or lacked the required fault element, they are disputing that the prosecution can prove its case, not introducing any new matter. This is simply the ordinary operation of the prosecution's burden of proof.

A true defence, by contrast, admits that the physical and fault elements are established and instead points to some further circumstance that excuses or justifies the conduct. A person who acted in self-defence typically accepts that they intentionally struck another person — the dispute is over whether that conduct was, in the circumstances, legally justified. This structural distinction matters because it changes what the accused needs to establish and what the prosecution must then answer.

Justificatory defences (such as self-defence) treat the conduct as having been the right thing to do, or at least a permissible thing to do, in the circumstances. Excusatory defences (such as duress) do not say the conduct was right, but recognise that the accused should not be held criminally responsible for it given the pressure they were under. This distinction is more theoretical than practical for most problem-question purposes, but it helps explain why the categories are structured as they are.

How defences are raised and resolved

In general terms, an accused who wishes to rely on a defence carries an evidential burden — they must point to sufficient evidence to make the defence a live issue on the facts. Once that evidential threshold is met, the legal burden typically falls on the prosecution to negative the defence beyond reasonable doubt, rather than on the accused to establish it on the balance of probabilities. Mental impairment is a notable, well-recognised exception to this general pattern, where the accused typically carries the onus on the balance of probabilities. The precise allocation of burdens, and the language used to describe each defence, differs between the Code jurisdictions — where defences are typically defined within the Code text itself — and the common-law jurisdictions, where defences are developed by the courts and then substantially modified by statute. A student should always confirm which framework governs before stating the elements of a specific defence with confidence.

The well-known defence categories

• Self-defence — conduct undertaken because the accused believed it was necessary to defend themselves or another person, and which was a reasonable response to the threat as the accused perceived it. Both the genuineness of the belief and the reasonableness of the response are typically in issue, per the modern test set out in Zecevic v Director of Public Prosecutions (Vic) (1987) 162 CLR 645.¹
• Duress — conduct undertaken because the accused was threatened with serious harm unless they committed the offence, leaving them, in the view of the law, with no realistic choice but to comply. Duress is generally unavailable for the most serious offences.
• Necessity (sudden emergency) — conduct undertaken to avoid an imminent peril, where breaking the law was, in the accused's genuine and reasonable assessment, the only way to avoid a greater harm. Necessity is conceptually close to duress but responds to circumstances generally rather than to a threat from another person.
• Mental impairment — conduct undertaken while the accused, because of a mental health impairment or cognitive impairment, did not understand the nature and quality of their conduct, or did not know it was wrong. A finding of mental impairment does not result in an acquittal in the ordinary sense; it typically leads to a special verdict and a different, care-oriented set of consequences rather than a conventional sentence.

In Victoria the statute has replaced the common law, and Edmunds v The King [2025] VSCA 31² is the case to read next to Zecevic. Emerton P, Taylor JA and Kidd AJA held that although s 322N of the Crimes Act 1958 (Vic) abolishes self-defence at common law, "the principles under the common law concerning the reliance of an original aggressor upon self-defence remain relevant". So Zecevic is not simply spent in the jurisdiction where it was decided — identify the applicable statutory test first, then ask which common law principles still inform it.

That last point is before the High Court. Special leave to appeal in Edmunds was granted on 7 May 2026³ and the appeal is a current case. Nothing has been overruled, so Edmunds remains the law in Victoria — but an answer that states the survival of the common law principles flatly, without noting that the question is on appeal, is incomplete.

Applying this in a problem question

1. Work through the offence elements first, and identify clearly which elements (if any) are genuinely disputed as a matter of denial.
2. Separately ask whether the facts raise a true defence that admits the elements but points to an excusing or justifying circumstance.
3. Identify which specific defence category is engaged, and note whether it is justificatory or excusatory in character.
4. Confirm which jurisdiction and which body of law — Code or common law — governs the defence before stating its elements.
5. Address the evidential burden first, then explain who carries the legal burden once that threshold is met.