Under NSW law, a person is not responsible for a criminal offence if the person carries out the conduct constituting the offence in self-defence.
It will be “self-defence” if at the time the conduct occurred:
the accused believed that the conduct was necessary in order to defend himself or herself; and,
the conduct of the accused was a reasonable response to the circumstances as he or she perceived them.
Although “self-defence” is referred to as a defence, in reality it is for the prosecution to eliminate it as an issue by proving beyond reasonable doubt that the accused’s act was not done by them in self-defence. It may do this by proving beyond reasonable doubt either:
that the accused did not believe at the time of the act that it was necessary to do what they did in order to defend themselves, or
the act by the accused was not a reasonable response in the circumstances as they perceived them.
If the Prosecution has failed to prove either one of the above, then the appropriate verdict is one of “not guilty”.
However, this is subject to a further direction of law that arises in cases when the accused has been charged with murder. In such cases if the Jury is satisfied the accused:
intentionally (or recklessly) used force thus causing death;
believed their conduct was necessary in self-defence;; but,
used force which was not a reasonable response in the circumstances as the accused perceived them,
then the appropriate verdict is one of “not guilty of murder” but “guilty of manslaughter”.
It is the accused perception which must be considered in determining whether what they did was a reasonable response to those circumstances. The matter should not be looked at with the benefit of hindsight, but in the realisation that calm reflection cannot always be expected in a situation such as the accused found themselves to be in.
If a Jury finds that an accused did have, or that it is reasonably possible that they may have had, that belief, it matters not that their belief may have been mistaken. If, however, the Prosecution establishes beyond reasonable doubt that the accused did not personally believe that their conduct was necessary for their defence, then the Prosecution will have succeeded in eliminating self-defence.
If a Jury is satisfied that the accused had, or that it is reasonably possible that he or she may have had, a belief that their conduct was necessary for their defence, then the Jury turn to the next question whether the conduct of the accused was not a reasonable response to the circumstances as perceived by the accused.
Even if the accused honestly was mistaken in their perception of those circumstances, provided a Jury is satisfied that it was, or might have been, their perception of the circumstances, and that the response was reasonable in those circumstances, the Prosecution will have failed to eliminate “self-defence”. The Prosecution will only have proven the the offence if it satisfies the Jury beyond reasonable doubt that the conduct of the accused was not a reasonable response in the circumstances as the accused perceived them to be at the time of the conduct in question.
All individual matters will turn on the evidence relating to the act, for example, the imminence of a threatened attack or the availability of other remedies to the accused, such as retreat. It is always, however, made emphatically clear to the Jury that it is the accused’s perception of the circumstances which must be considered.