A person who pleads not guilty to a criminal offence may rely on a legal defence or a factual defence. A factual defence is a version of events that is inconsistent with the accused having carried out the acts alleged – for example, an alibi. A legal defence exists where the accused admits carrying out the acts but had a justification for doing so. This page outlines some of the main criminal defences that can be relied on in Australia.
Criminal defences in different states and territories
It is important to note that each state and territory of Australia has its own criminal laws. Criminal defences are defined and constituted differently in different jurisdictions. Aside from the defences outlined below, there are also other defences that apply to particular offences set out in the legislation of the states and territories. All of the defences outlined below exist in some form in every state and territory.
Self-defence
Self-defence is a legal defence that can be relied on in response to any charge involving the unlawful use of force, such as assault and murder. For the defence of self-defence to succeed, the accused must have used a level of force that was proportionate to the extent of the threat they believed they were facing.
To defeat a charge on the basis of self-defence, the defendant must be found to have:
- held a genuine belief that it was necessary to use force to protect themselves or someone else from harm;
- used a level of force that was proportionate to the threat they perceived; and
- had reasonable grounds for that belief and that use of force.
Once the defence has raised self-defence, the prosecution bears the burden of proving that the act was not committed in self-defence.
Consent
Consent is a defence to criminal charges involving unwanted sexual contact where the alleged victim is an adult – such as rape and indecent assault. A person who is charged with one of these offences will not be found guilty if the court finds that the sexual contact was consensual.
Consent means free agreement, voluntary agreement or consent that is given freely and voluntarily. In all states and territories, a person is not taken to have consented validly if their consent was given because of fear or force or while they were asleep, unconscious or so intoxicated that they were not capable of consenting.
In some states and territories, an accused person may rely on the defence of consent if they held a reasonable but mistaken belief that the alleged victim was consenting. In others, the defence of consent is only available if the alleged victim was actually consenting.
Mental impairment
Every jurisdiction has a defence that applies where the accused was mentally impaired at the time of the alleged offence and did not have the capacity to understand or control their actions. This defence is variously known as mental impairment, mental illness and insanity.
If a person is acquitted on this basis, they cannot be dealt with by the criminal courts. Instead, they must be dealt with by dedicated courts and tribunals for managing people who have been found not guilty of offences because of mental impairments.
A person may be made subject to an order that requires them to undergo psychiatric care or treatment, either while living in the community or while detained in a mental health facility.
Emergency
In all jurisdictions, a person may be acquitted of a criminal offence if they committed the act because of a sudden and extraordinary emergency. When the defence raises the defence of emergency, the prosecution then has the burden of proving that the accused was not acting in response to an emergency.
The test used to determine whether a person should be found not guilty on the basis of emergency is whether they acted in a way that is what could be expected of an ordinary person. The court must consider the circumstances as they appeared to the accused in the moment and not with the benefit of hindsight.
Automatism
A person may rely on the defence of automatism if they are charged with an offence arising from an act that they did not have control over. Examples of where an accused may be found not guilty on the basis of automatism are where an act was committed while the person was sleepwalking or where an act was the result of an involuntary physical reflex.
Where this defence is raised, the prosecution must prove that the accused acted voluntarily.
Mistake of fact
The defence of honest and reasonable mistake of fact can be relied on only in very limited circumstances in response to a charge that is a strict liability offence.
A strict liability offence is an offence that does not require the accused to have had a particular state of mind such as intention or recklessness. If the accused is charged with a strict liability offence and held a mistaken belief of fact that, if it had been correct, would have rendered their actions innocent, they may be found not guilty. For example, if a person held a mistaken belief that they held a valid driver’s licence at the time they were charged with unlicensed driving, they may be acquitted on this basis.
It is important to note that the defence of mistake cannot be relied on if the accused was mistaken about a matter of law.
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