The partial defence of “substantial impairment because of a mental health impairment” will succeed if the accused has established more probably than not, both that:

As to the first matter, the issue is whether the accused’s capacity to function in one or other of the three ways was substantially impaired, not whether [he/she] simply chose not to function in that way.

A person has a mental health impairment if each of the following three matters have been proved:

[Delete unnecessary elements of (a) and (c).]

[Where appropriate: A person does not have a mental health impairment if the person has an impairment caused solely by either:

“Impaired” has its ordinary meaning and requires proof of a capacity less or lower than the normal range.

“Substantial” also has its ordinary meaning of being “of substance” and “not slight or insignificant”.

As to the second matter, the issue as to whether an impairment was so substantial as to warrant liability for murder being reduced to manslaughter calls for a value judgment applying community standards.]

[Where appropriate s 23A(3) — self-induced intoxication:

The effect of self-induced intoxication from drugs and/or alcohol at the time of the act(s) causing the death are to be disregarded in the assessment of both of these matters at 1 and 2 above.]

If the accused has not established the partial defence of substantial impairment because of mental health impairment, the appropriate verdict is one of “guilty of murder”.

If the accused has established the partial defence of substantial impairment by abnormality of mind, you must find [him/her] “not guilty of murder but guilty of manslaughter”.]

I next come to what has been shortly referred to during the trial as “substantial impairment”. This only arises for your consideration if you are satisfied beyond reasonable doubt that the Crown has established all of the essential ingredients of the crime of murder [where appropriate: including negating (disproving) the issue of self defence and/or provocation and/or that you are not satisfied on the balance of probabilities the accused is not criminally responsible because of a mental health impairment, a cognitive impairment, or both]. If that is the case, you next have to come to this question of substantial impairment.

The law provides that a person who would otherwise be guilty of murder is not to be convicted of that offence, but is to be convicted of the offence of manslaughter, if at the time of the act causing the death concerned [his/her] capacity either to understand events, or to judge whether [his/her] actions were right or wrong, or to control [himself/herself], was substantially impaired because of a mental health impairment; and furthermore, that that impairment was so substantial as to warrant liability for murder being reduced to manslaughter.

It is called a “defence to murder” because it is for the accused to raise it and to prove it. To do so, however, [he/she] is not put to the strict standard of proof beyond reasonable doubt which is required of the Crown. The standard of proof on the accused is on the balance of probabilities. This means that if, at the end of your deliberations, you are of the view that it is more likely than not that what the accused claims in respect of this defence is so, then [he/she] has succeeded. It is called a “partial defence” because, if it does succeed, then the appropriate verdict is “not guilty of murder but guilty of manslaughter”.

[Where appropriate, add:

Rationale

Before turning to a more detailed discussion of the ingredients of this partial defence, I should first briefly explain the reasons why Parliament has provided for it. Persons charged with committing a crime, if convicted, are to be punished for it. One of the most important factors in determining what punishment should be imposed for the crime of which he or she is convicted is whether there are matters in mitigation which would serve to reduce the extent of the blame which should attach to that crime.

Although both involve the death of a human being, the crime of murder is a more serious crime than the crime of manslaughter, and hence manslaughter is punished less severely than murder. This is so for a number of reasons, one of which is that the culpability of a person who commits the crime of manslaughter is less than that of a person who commits the crime of murder.

A person who, because of a mental health impairment has an impaired capacity either to understand events; to judge whether his or her actions were right or wrong; or to control himself or herself, is less responsible, according to the standards prevailing in our community, than a person who has full capacity in those respects.

With reference to the capacity to understand events, it is important that you should consider the accused’s perception of events. These include [his/her] perception of physical acts and matters, the surrounding circumstances, what [he/she] was doing and its effects.

Accordingly, Parliament has provided for this defence which requires not only that the accused prove that [his/her] capacity was so impaired, but also requires that you, as the jury representing the community and applying the standards which you regard as current in the community, are satisfied that the impairment was so substantial that the liability of the accused to punishment should be reduced from that which would follow from a conviction of murder, to that which would follow from a conviction of manslaughter. Because the onus is on the accused in respect of these matters, as an exception to the general rule that the onus of proof is on the Crown, the standard of proof is the lesser standard of “on the balance of probabilities” rather than the higher standard of “proof beyond reasonable doubt” required of the Crown.]

Substantial impairment

Turning now to what is involved in this partial defence, there two matters which the accused must prove. The first matter is that at the time of the … [specify act, for example, stabbing, shooting etc] causing the death charged, [his/her] capacity either to understand events, or to judge whether [his/her] actions were right or wrong or to control [himself/herself] was substantially impaired because of a mental health impairment.

A person has a mental health impairment if each of the following three matters have been proved:

[It will often not be necessary to refer to every aspect of (a) and (c); only to those which have been specifically raised by the evidence.]

[Discuss each of these three matters in turn by referring to the evidence and the submissions of the parties.]

[Where appropriate: A person does not have a mental health impairment if the person has an impairment caused solely by either:

[Discuss either or both matters by reference to the evidence and the submissions of the parties.]].

“Impaired” has its ordinary meaning and requires proof of a capacity less or lower than the normal range.

“Substantial” also has its ordinary meaning of being “of substance” and “not slight or insignificant”.

In determining whether the accused has established that it is more likely than not that at the time of the act [specify] [his/her] capacity to understand events, to judge whether [his/her] actions were right or wrong, or to control [him/herself] was substantially impaired by a mental health impairment, you will need to carefully consider the evidence of the psychiatrists (or other expert witnesses). These are areas in which psychiatrists … [etc, specify] have particular expertise and experience.

You are not bound, however, to accept their evidence. You are entitled to act on other evidence in the case if you think that there is other evidence which conflicts with or undermines the basis upon which the psychiatrists expressed their opinions.

On the other hand, you would obviously pay careful and close attention to what the opinion evidence is as to these matters because of the experience and expertise which these witnesses have in this field.

You would only decline to act on the evidence of the psychiatrists [and psychologists] if you think that there is other evidence which outweighs the psychiatric evidence, or if you think that the facts differ from those on which the psychiatrists based their opinions, or if you think that the reasons expressed by the psychiatrists for their opinions (even having regard to their expertise) do not support their conclusion … [a different direction would need to be given if, as often happens, the psychiatric or psychological evidence reaches different conclusions].

Substantial impairment such as to warrant liability for murder being reduced to manslaughter

The second matter which the accused must prove is whether the substantial impairment relied upon by the accused was so substantial as to warrant [his/her] liability for murder being reduced to manslaughter.

This will only arise for consideration if the accused has satisfied you as to the first matter that there was a substantial impairment as I have described.

In deciding this second matter you must apply the standards which you regard as prevailing in our community (bearing in mind that manslaughter is regarded as a less serious crime than murder, and that the community places less blame and condemnation upon a person guilty of manslaughter than of murder). In answering this question, you should approach the matter in a broad common sense way, applying (as I have said) the standards of the community which you are here to represent.

The question you should ask yourself is — “Has the accused satisfied you in the circumstances of this case that any impairment to [his/her] capacity (if you find that it is likely to have existed) was such that [he/she] should not be condemned or blamed as a murderer, and that rather, [he/she] should be treated as having been guilty of manslaughter?”.

[Where appropriate s 23A(3) — self-induced intoxication:

The effect of self-induced intoxication from drugs and/or alcohol at the time of the act(s) causing the death are to be disregarded in the assessment of both matters that the accused is required to prove. You must consider both of them on the assumption that the accused was not affected by intoxication from drugs and/or alcohol.]

To summarise then, if, on the one hand, you have been satisfied by the Crown beyond reasonable doubt of all of the necessary matters which it has to establish in order to justify a conviction of murder, and also that the accused, on the other hand, has satisfied you that it is more likely than not that this partial defence is made out, the appropriate verdict is “not guilty of murder but guilty of manslaughter”.

If, however, you have been satisfied by the Crown beyond reasonable doubt of all that it must prove to justify a conviction for murder, but the accused has failed to satisfy you that it is more likely than not that this partial defence has been made out, the appropriate verdict is one of “guilty of murder”.