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The Defence of Self-Defence

Self-defence is a legal defence that is available to an accused person who uses force in response to a perceived threat of harm. The defence of self-defence allows the accused person to claim that their actions were justified because they were necessary to protect themselves or another person, or property from harm. This page deals with the defence of self-defence.


The defence of self-defence is set out in the criminal law legislation of different states and territories and elaborated on in Australian case law. The leading case on self-defence in Australian is the 1987 High Court decision of Zecevic.

What is required for self-defence to succeed?

To successfully raise the defence of self-defence, the accused person must establish the following elements:

  • The accused person believed on reasonable grounds that it was necessary to use force to defend themselves or someone else from imminent unlawful harm.
  • The force used by the accused person was reasonable in the circumstances, meaning that it was proportionate to the perceived threat.
  • The accused person’s belief and the force used must have been based on reasonable grounds. This means that the accused person’s actions must have been objectively reasonable, given the circumstances as the accused person perceived them.

Burden of proof

While the defence bears the burden of raising the defence of self-defence, the onus then shifts to the prosecution to disprove any one of the elements set out above beyond a reasonable doubt. If the prosecution cannot prove beyond a reasonable doubt that the accused was not acting in self-defence, the accused will be acquitted of the offence.

When can self-defence not be used?

It is important to note that self-defence cannot be used as a defence if the accused person was the aggressor or if they used excessive force in response to a perceived threat. Additionally, the use of force must be proportionate to the perceived threat.

The defence of self-defence will not be available if the accused person used excessive force – for example, killing an attacker in response to a non-lethal attack, or causing serious harm to a person in defence of property.

Zecevic v DPP

The High Court of Australia decision in Zecevic v Director of Public Prosecutions (1987) is the main authority for the defence of self-defence. The case involved the accused killing his neighbour and using self-defence as a defence. The accused argued that his actions were necessary as he believed the victim possessed a knife and a shotgun, which justified him retrieving his gun and shooting the man.

The court established the following test for assessing the applicability of self-defence in any case:

‘The question to be asked in the end is quite simple. It is whether the accused believed upon reasonable grounds that it was necessary in self-defence to do what he did. If he had that belief and there were reasonable grounds for it, or if the jury is left in reasonable doubt about the matter, then he is entitled to an acquittal. Stated in this form, the question is one of general application and is not limited to cases of homicide.’

Effect of self-defence

A person who committed an act in self-defence is not guilty of any offence. A person who successfully argues the defence of self-defence will receive a full acquittal.

If you require legal advice or representation in any legal matter, please contact Armstrong Legal.

Fernanda Dahlstrom

This article was written by Fernanda Dahlstrom

Fernanda Dahlstrom has a Bachelor of Laws, a Bachelor of Arts and a Graduate Diploma in Legal Practice. She has also completed a Master’s in Writing and Literature. Fernanda practised law for eight years, working in criminal defence, child protection and domestic violence law in the Northern Territory and in family law in Queensland.

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