The Act Commentary on Sections Part 2 - Criminal offences Section 55:  Meaning of “qualifying trigger”
343.Section 55 defines the term “qualifying trigger” for purposes of section 54. Under section 54 (1)(b) the loss of self-control must have a qualifying trigger in order for the partial defence to apply.
344.Subsections (2) to (5) set out that the qualifying triggers for a loss of self-control are where the loss of self-control was attributable to a fear of serious violence, to certain things done or said (or both) or to a combination of both of these.
345.Subsection (3) deals with cases where the defendant lost self-control because of his or her fear of serious violence from the victim. As in the complete defence of self-defence, this will be a subjective test and the defendant will need to show that he or she lost self-control because of a genuine fear of serious violence, whether or not the fear was in fact reasonable. The fear of serious violence needs to be in respect of violence against the defendant or against another identified person. For example, the fear of serious violence could be in respect of a child or other relative of the defendant, but it could not be a fear that the victim would in the future use serious violence against people generally.
346.Subsection (4) sets out when a thing or things done or said (or both) can amount to a qualifying trigger for the loss of self-control. The thing(s) done or said must amount to circumstances of an extremely grave character and cause the defendant to have a justifiable sense of being seriously wronged. Whether a defendant’s sense of being seriously wronged is justifiable will be an objective question for a jury to determine (assuming that there is sufficient evidence for the defence to be left to the jury).
347.Subsection (4) therefore sets a very high threshold for the circumstances in which a partial defence is available where a person loses self-control in response to words or actions. The effect is to substantially narrow the potential availability of a partial defence in cases where a loss of control is attributable to things done or said compared to the current partial defence of provocation (where no threshold exists in relation to the provoking circumstances).
348.Subsection (5) allows the loss of self-control to be triggered by a combination of a fear of serious violence and a thing or things done or said which constitute circumstances of an extremely grave character and cause the defendant to have a justifiable sense of being seriously wronged.
349.Subsection (6) makes further provision in relation to determining whether a loss of self-control has a qualifying trigger:
	Subsection (6)(a) provides that, when the defendant’s fear of serious violence was caused by something that the defendant incited for the purpose of providing an excuse to use violence, it is to be disregarded. The effect is that, in such a situation, the person would not be able to claim a partial defence based on his or her fear of serious violence as referred to in section 55(3).
	Subsection (6)(b) provides that, when the defendant’s sense of being seriously wronged by a thing done or said relates to something that the defendant incited for the purpose of providing an excuse to use violence, the sense of being seriously wronged is not justifiable. The effect is that, in such a situation, the person would not be able to claim a partial defence based on the relevant things done or said as referred to in section 55(4).
	Subsection (6)(c) provides that, in determining whether a loss of self-control has a qualifying trigger, the fact that a thing done or said amounted to sexual infidelity is to be disregarded. So, if a thing done or said, as referred to in section 55(4), amounts to sexual infidelity, that fact is disregarded in determining whether the qualifying trigger in section 55(4) applies. The effect is that, if a person kills another because they have been unfaithful, he or she will not be able to claim the partial defence. It is the fact of sexual infidelity that falls to be disregarded under the provision, so the thing done or said can still potentially amount to a qualifying trigger if (ignoring the sexual infidelity) it amounts nonetheless to circumstances of an extremely grave character causing the defendant to have a justifiable sense of being seriously wronged. This may arise only rarely, but an example of where it might be relevant is where a person discovers their partner sexually abusing their young child (an act that amounts to sexual infidelity) and loses self-control and kills. The fact that the partner’s act amounted to sexual infidelity must be discounted but that act may still potentially be claimed to amount to the qualifying trigger in section 55(4) on the basis of the other aspects of the case (namely the child abuse).