In the case of a home invasion (that is, a serious criminal trespass in a place of residence), acting for a defensive purpose or to defend property can be complete defences to an offence, including murder, even if the defendant's conduct was not objectively reasonably proportionate to the perceived threat [s15C Criminal Law Consolidation Act 1935 (SA)].

What is required is that the defendant genuinely believed that the victim was committing or had just committed a home invasion [s 15C(2)(a)].

This section is not available if the victim was an on-duty police officer [s 15C(1)(b)], or if the defendant was themselves engaged in criminal activity that might have given rise to the threat [s 15C(2)(b)], or if the defendant was affected by drugs (unless involuntarily taken, or prescribed or over-the-counter and used appropriately [s 15C(2)(c)].