Self-Defence Laws in the ACT: Section 42 Explained

Under section 42 of the Criminal Code 2002 (ACT), a person is not criminally responsible for an offence if they believed the conduct was necessary for a listed purpose, such as defending themselves or someone else, ending an unlawful imprisonment, protecting property, or dealing with a trespasser, and the conduct was a reasonable response in the circumstances as they perceived them, but that excuse is unavailable if they intentionally inflict death or serious harm only to protect property or deal with a trespasser, or if they know they are responding to lawful conduct.

The Test Under Section 42

Section 42 says a person is not criminally responsible for an offence if they carried out the conduct in self-defence. They do so only if they believed the conduct was necessary for one of five purposes: to defend themselves or someone else; to prevent or end the unlawful imprisonment of themselves or someone else; to protect property from unlawful appropriation, destruction, damage or interference; to prevent criminal trespass to land or premises; or to remove a person committing criminal trespass from land or premises. The conduct must also be a reasonable response in the circumstances as the person perceived them. It is the same two-limb structure used in New South Wales' section 418 and the Northern Territory's section 43BD, reflecting the Commonwealth Criminal Code model that the ACT's general principles are built on.

What "Reasonable Response" Means

The test separates what the person believed from whether their response was reasonable. Belief is assessed on the person's own honest state of mind, whether they genuinely thought the conduct was necessary for one of the five listed purposes. Reasonableness of the response is then judged objectively, but anchored to the circumstances as that person perceived them, not to the circumstances as they turned out to be. Section 42 does not define "reasonable" beyond that structure, and no further ACT-specific gloss was located in this research.

Property, Trespass and the Limits on Force

Section 42(3) takes the excuse away in a defined set of situations. It applies to only three of the five purposes in section 42(2), protecting property, preventing criminal trespass, and removing a trespasser, and does not touch the purposes of defending a person or ending an unlawful imprisonment. Within that narrower scope, it applies where a person uses force that involves the intentional infliction of death or serious harm.

"Serious harm" is defined in the Criminal Code 2002's own dictionary as any harm, including the cumulative effect of more than one harm, that endangers or is likely to endanger human life, or is, or is likely to be, significant and longstanding. That second limb does not require a risk to life, which means it can capture some injuries that would sit below the common-law concept of grievous bodily harm, and it means the section 42(3) threshold is not simply "GBH" under another name.

A second, separate branch of the same exclusion, section 42(3)(b), removes the excuse if the person is responding to conduct they know is lawful, for example resisting a lawful arrest. Section 42(4) clarifies that conduct is not treated as "lawful" for that purpose merely because the person carrying it out happens to be excused from criminal responsibility for it.

Defending Your Home

The ACT has no separate dwelling or castle-doctrine provision. Checking the full text of both the Criminal Code 2002 and the Crimes Act 1900 (ACT), the word "dwelling" appears only in a search-warrant provision unrelated to self-defence. A confrontation with an intruder in a home is assessed under the same general section 42 test, including the section 42(3) property exclusion described above, as any other property or trespass scenario.

No Excessive Self-Defence in the ACT

The Criminal Code 2002 does not define homicide offences and contains no reference to manslaughter at all. The Crimes Act 1900 (ACT), which does define murder (section 12) and manslaughter (section 15), sets out only two partial defences that reduce murder to manslaughter: provocation (section 13) and diminished responsibility (section 14). Neither touches self-defence or the proportionality of a response, and section 13(6) confirms that ordinary section 42 self-defence continues to operate in full alongside those two partial defences. That means self-defence in the ACT works on an all-or-nothing basis on a murder charge: it either succeeds and the person is not criminally responsible, or it fails and there is no separate, scaled-down verdict available on the strength of self-defence alone.

Retreat

No retreat requirement was found. The word "retreat" does not appear in either the Criminal Code 2002 or the Crimes Act 1900 (ACT). Section 42(2)(b)'s "reasonable response... as perceived" wording is the only test that applies.

Family Violence

Checking three primary sources, the Criminal Code 2002, the Crimes Act 1900, and the Family Violence Act 2016, this research found no ACT provision that modifies the section 42 test for family violence, the way Victoria's section 322M or Queensland's section 304B do. Family violence appears in the Criminal Code 2002 only in unrelated protection-order cross-references, and in the Crimes Act 1900 only in aggravated-offence and sentencing contexts, never in connection with self-defence. The Family Violence Act 2016 governs protection orders and does not mention self-defence at all. That is a documented negative, not a finding that family violence context is irrelevant to a case, and it is separate from applying for a protection order under civil law. See Australia's AVO laws and family violence and parenting orders in Australia.

Intoxication

Section 33 sets the general intoxication rules. For elements based on actual belief, intoxication evidence can be considered unless the offence has a basic-intent fault element and the intoxication was self-induced. For elements based on reasonable belief, the standard is a sober reasonable person, unless the intoxication was not self-induced, in which case it becomes a reasonable person intoxicated to the same extent. Section 42(2)(a)'s "believes" limb fits the first rule. Section 42(2)(b)'s "reasonable response... as perceived" wording mixes a subjective and an objective element, and the statute does not spell out which part of section 33 governs the perception half of that limb. That interaction is a genuine textual ambiguity that this research left open; it would need a case-law pass to resolve.

Carrying Something for Self-Defence

Carrying an item because you want it "for self-defence" is not, on its own, a lawful excuse under the ACT's weapons laws. Capsicum spray is prohibited for civilian self-defence use in the ACT, and the Crimes Act 1900 (ACT) expressly states, at section 382(3), that carrying a knife in public or at school solely for the purpose of self-defence or defending someone else is not a reasonable excuse. See self-defence weapons in Australia for the state-by-state position, firearms licensing in Australia for why self-defence is not treated as a genuine reason for a licence, and prohibited weapons in Australia.

After You've Used Force

What happens after a self-defence incident, arrest, police interview, the right to silence, and the right to a lawyer, is covered separately at Miranda rights in Australia, which explains how those protections work under the uniform Evidence Act that applies in the ACT. This page describes the self-defence test itself; it is not a guide to what to do or say during a police interview, and nothing here should be read as advice to act in a particular situation. For the near-universal pattern across all eight Australian jurisdictions, see self-defence laws in Australia.