The loss of control defence came into force in October 2010, replacing the old defence of provocation. It is a partial defence to murder only, reducing it to manslaughter. It has three components, as laid out in Section 54-56 of the Coroners and Justice Act 2009:

(1) Where a person (“D”) kills or is a party to the killing of another (“V”), D is not to be convicted of murder if—

(a) D’s acts and omissions in doing or being a party to the killing resulted from D’s loss of self-control,

(b) the loss of self-control had a qualifying trigger, and

(c) a person of D’s sex and age, with a normal degree of tolerance and self-restraint and in the circumstances of D, might have reacted in the same or in a similar way to D

This defence does not apply if, doing or being a party to the killing, D acted in a considered desire for revenge.

The CJA 2009 further defines each section:

A. Loss of control: this does not have to be sudden [consider victims of domestic violence.

B. Qualifying trigger: this may include any combination of the following:

1. 1. 1. If D’s loss of self-control was attributable to D’s fear of serious violence from V against D or another identified person.
      2. If D’s loss of self-control was attributable to a thing or things done or said (or both) which constituted circumstances of an extremely grave character, and caused D to have a justifiable sense of being seriously wronged.

In determining whether there was a qualifying trigger:

• • • • • D’s fear of serious violence or sense of being seriously wronged is to be disregarded to the extent that it was caused by a thing which D incited to be done or said for the purpose of providing an excuse to use violence.
        • The fact that a thing done or said constituted sexual infidelity is to be disregarded.

C. ‘The circumstances of D’: is a reference to all of D’s circumstances other than those whose only relevance to D’s conduct is that they bear on D’s general capacity for tolerance or self-restraint. 

If sufficient evidence is raised for the defence, it is on the prosecution to prove it beyond a reasonable doubt that the criteria are not met.

1. Mental ill health may be relevant to the loss of self-control, trigger and the circumstances, but not the tolerance and self-restraint: Rejmanski [2017] EWCA Crim 2061

This appeal considered multiple cases relating to mental health conditions (including PTSD and EUPD). The case of Rejmanski claimed a defence of loss of control based on PTSD. The appeal was dismissed with the following comments made:

“…the first, and insurmountable, hurdle faced by the Appellant was that, if and insofar as his PTSD did affect his general capacity for tolerance and self-restraint, that was irrelevant to the third component of the defence… this is precisely the kind of consideration that Parliament expressly excluded at this stage. The hypothetical person is assumed to have a normal degree of tolerance and self-restraint.”

Attorney General for Jersey v Holley [2005] UKPC 23, [2005] 2 AC 580: it was accepted that in the case of a woman suffering from ‘Battered Woman’s Syndrome’ or a personality disorder, who killed her abuser, evidence of her condition may be relevant to both the loss of self control and to the gravity of the provocation for her.

R v Mcgrory [2013] EWCA Crim 2336: A “reduced ability to deal with taunting and to cope with those sorts of pressures compared to someone not suffering from depression“, was excluded.

R v Wilcocks [2016] EWCA Crim 2043, [2017] 1 Cr App R 23:

“If and in so far as you conclude a personality disorder reduced his general capacity for tolerance or self-restraint, that would not be a relevant circumstance when you are considering the defence of loss of control. But it is important to emphasise that this exclusion only relates to any feature of a personality disorder which reduced his general capacity for tolerance or self-restraint. Let me give you an illustration. If you thought that CW suffered from a personality disorder which made him unusually likely to become angry and aggressive at the slightest provocation, that would of course be relevant to diminished responsibility but it could not assist him in relation to loss of control. But if you thought that a personality disorder had caused him to attempt suicide, then you would be entitled to take into account as one of his circumstances the effect on him of being taunted that he should have killed himself.”

The impact of mental illness on self-control may instead form the basis of a defence of diminished responsibility, and the two defences may be presented together as alternatives.

2. Sexual infidelity is not sufficient as a sole qualifying trigger, but may be taken into account where other qualifying triggers exist: R v Clinton [2012] EWCA Crim 2