Western Australia’s Criminal Code and common law provide a range of defences that can result in an acquittal or a reduction in the charge. Understanding which defences apply to your circumstances — and how to build the evidence to support them — is the work of criminal defence from day one.
Western Australian criminal law recognises a range of defences — some created by the Criminal Code, others preserved at common law. A successful defence results in an acquittal. In some cases, a partial defence reduces the charge to a less serious offence. Which defences are available, and how strong they are, depends entirely on the specific facts of each matter.
Self-defence under the Criminal Code requires demonstrating that the accused believed on reasonable grounds that the conduct was necessary to defend themselves or another person from harm. Whether that belief was reasonable is assessed objectively — from the perspective of a reasonable person in the same situation. The forensic presentation of evidence is decisive: CCTV footage, medical evidence, witness accounts, and the sequence of events all bear on whether the belief was objectively reasonable.
The same framework applies where the accused acted to defend a third party. The accused must have reasonably believed that the conduct was necessary to protect that person from harm, and the conduct must have been reasonable in the circumstances as the accused understood them.
Duress is available as a complete defence where the accused was compelled to commit the offence under an immediate threat of death or grievous bodily harm, from which there was no reasonable opportunity to escape. The threat must have been operating at the time of the conduct and proportionate to the response. Duress is not available for murder in Western Australia.
For property offences, an accused who genuinely believed they had a legal right to the property cannot be convicted, even if that belief was mistaken. The belief must be genuine — not necessarily legally correct — and must relate to a claim of legal right, not merely a moral entitlement.
Under the Criminal Law (Mentally Impaired Accused) Act 1996 (WA), a person is not criminally responsible where, at the time of the conduct, a mental impairment meant they did not understand the nature of their actions, or did not know they were doing wrong. The accused bears the onus of establishing this defence on the balance of probabilities. A successful outcome results in a not guilty finding by reason of unsoundness of mind.
Involuntary intoxication may provide a complete defence where it negates the mental element of the offence. Voluntary intoxication has a more limited role — it may be relevant to whether the accused had the specific intent required, but does not excuse conduct that would be criminal regardless of intent.
Under section 23B of the Criminal Code, a person is not criminally responsible for an event that occurs by accident — that is, one that was not reasonably foreseeable as a consequence of the accused’s conduct. This defence is most commonly raised in assault matters where the accused claims the physical contact or its consequences were not intentional or foreseeable.
Consent is relevant in a range of offences, most significantly sexual offences. In Western Australia, consent must be freely and voluntarily given. A person does not consent if they are asleep or unconscious, intoxicated to the point of incapacity, submitting under threat or force, or deceived about the nature of the act. Consent cannot be assumed from the absence of protest.
The most fundamental defence in any matter is a direct challenge to whether the prosecution can prove the elements of the charge beyond reasonable doubt. Identification evidence, CCTV reliability, witness credibility, forensic evidence integrity, and the sufficiency of the prosecution’s case are all subject to challenge. The prosecution bears the burden — if any reasonable doubt exists, the accused must be acquitted.
Identifying which defences apply to your circumstances, gathering the evidence to support them, and deciding whether to contest the charge or seek a negotiated resolution are all decisions that must be made with specialist legal advice — and made early. Opportunities to gather evidence, identify witnesses, and preserve records narrow as time passes. Speak with a criminal defence lawyer before you respond to the charge or make any decision about your plea.
Need to understand your defence options in Western Australia?
Clear, honest advice on which defences apply to your circumstances — from day one.