Every Accused charged with an offence may present evidence that the offence was committed in self-defence and/or the defence of others. Persons who themselves are the target of violence or the threat of violence may use reasonable force to defend themselves. Likewise, a person may use reasonable force in the defence of another party.
In this case, a fight ensued wherein the complainant was armed with a machete and a knife while the Accused wielded a hammer. At some point the Accused struck the complainant’s hand with the machete. A new trial was ordered on appeal after the trial judge failed to instruct the jury to consider self-defence and/or in the defence of a third-party.
The test for if a defence should be left with the jury, ie. whether there is an “air of reality” to the proposed defence, is three-fold. Is there evidence on which a jury could reasonably find that each of the three criteria of self-defence and/or defence of others were not disproven beyond a reasonable doubt:
(a) could a jury reasonably conclude that the Accused believed on reasonable grounds that force or threat of force was being used against them or someone else;
(b) could a jury reasonably conclude that the subjective purpose of the defensive act was for the Accused to protect themselves or others; and
(c) the reasonableness of the force used.
https://www.canlii.org/en/on/onca/doc/2020/2020onca259/2020onca259.html