Self Defence in South Australian Criminal Law

By James Cobiac


It is a defence to certain allegations if the defendant can prove, on the balance of probabilities that they were acting for a defensive purpose. The defendant must hold a genuine belief that at the time they exercised their defensive conduct for which they have been charged that the conduct was necessary and reasonable to defend either themselves or another. Additionally, the defendant must also demonstrate that their actions in the circumstances, as they perceived them, were reasonably proportionate to the threat they believed they were confronted with (Criminal Law Consolidation Act 1935 (SA), s 15(1)(a)-(b)).

There a number of important considerations concerning the formula of law stated above. Firstly, the requirements of self-defence envisage some degree of force enacted by an accused against a threat. This distinguishes a plea of self-defence from the less commonly pleaded defence of necessity (a different defence that may be available but is beyond the scope of this blog). Secondly, the law requires the defendant to hold a genuine belief that their conduct was necessary in the circumstances as they perceived them to be. This requires an exploration of the defendants subjective state of mind at the time that the threat arose. For example, confrontation by a large attacker whom the accused knows to be violent could be capable of giving rise to physical violence that could otherwise be characterised as an assault that is necessary and reasonable for a defensive purpose.

This also brings into play the further requirement that the conduct be proportionate to the threat that the accused genuinely believes to exist. Proportionality is measured objectively by reference to the threat that the defendant believes to exist, not the actual threat. Taking our current example, the defendant genuinely believes he is being confronted by a large aggressive attacker that is known to him. This is the threat that the defendant’s conduct will be measured against objectively, regardless of whether the defendant has mistaken the threat in an objective sense. It is also important to note that defensive actions need not perfectly equate to the force they respond to. For example, perceiving a larger attacker it may be that the accused is justified in using a weapon for a defensive purpose and exceed the force used against them. This is a matter of fact and degree in each individual circumstance of offending. If the defendant’s conduct is found to be disproportionate, it may still be taken into account when they are sentenced; and may be powerful in mitigation.

There are some other aspects informing the law surrounding self-defence. If the conduct is found to be out of proportion to the threat perceived by the defendant in the case of a murder charge, then the charge will be downgraded to the lesser charge of manslaughter because an intent to kill is undermined by the established intent to defend oneself. Further, self-defence can be argued where conduct is used to defend another, or property. However, it cannot be argued if the defendant was resisting a lawful arrest wherein the police officers are exercising force reasonably necessary to subdue the defendant. Finally, proportionality operates differently where the action is taken in defence to a home invasion in circumstances where the defendant is not engaged in criminal misconduct that could give rise to the invasion, or is being arrested by a police officer, or is intoxicated. In these circumstance proportionality need not be reasonable. This concept is complex and a lawyer should be consulted if you have been charged with criminal offending and think a plea of self-defence is open to you.

Culshaw Miller Criminal Lawyers are available 24 hours a day to provide advice or attendance on 0418 421 153 an appointment you can contact our offices on (08) 8464 0033.