8.8 - Mental Impairment
8.8.2 - Charge1
Warning! The law is currently unclear on when this direction should be
given within a charge. See the Bench Notes for guidance on that issue.
Introduction
In this case, defence counsel2 has raised what is called the “defence of
mental impairment”, submitting that NOA should be found not guilty of
[insert name of offence] because s/he was mentally impaired when s/he
[insert relevant acts]. I therefore need to give you some directions about
this defence.
Onus and Standard of Proof
According to the law, people should not be held criminally responsible for
acts they do while suffering particular effects of a mental impairment. So
even if the prosecution can prove, beyond reasonable doubt, that NOA
[identify matters the prosecution must prove],3 s/he will not be guilty of
[identify offence] if s/he committed those acts while suffering certain
mental conditions.
However, in the absence of any evidence to the contrary, the law
presumes that people are not mentally impaired. So if you are to find that
NOA was not guilty because of a mental impairment, it is the defence who
must prove that s/he was mentally impaired at the time s/he [did the acts
/ made the omissions] said to constitute the crime.
You can see that this is one of those rare situations in which a matter
must be proved by the defence. The prosecution must still prove [identify
matters the prosecution must prove] before you need to consider the
issue of mental impairment. However, if you are satisfied that those
matters have all been proven, it is defence counsel who must prove the
requirements of this defence if you are to find the accused not guilty
because of mental impairment.
1
This document was last updated on 23 November 2011.
This charge is based on the assumption that the defence has raised the issue of
mental impairment. If it is the prosecution that has raised the issue, the charge
will need to be modified accordingly.
2
It is unclear precisely which matters the prosecution must prove (see “Mental
Impairment and Proof of Elements” in the Bench Notes). The content of this part
of the charge, as well as similar sections below, will depend on how the judge
resolves the issues outlined in the Bench Notes.
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Unlike the elements of the offence – which the prosecution must prove
beyond reasonable doubt – the defence only needs to prove these
requirements on what is called the “balance of probabilities”. This is a
much lower standard than that required of the prosecution when proving
an offence. It only requires the defence to prove that it is more probable
than not that NOA was mentally impaired to the necessary degree.
Overview of Requirements
There are two requirements that the defence must prove, on the
balance of probabilities, if you are to find the accused not guilty because
of mental impairment. I will list them for you, and then explain each one
in more detail.
First, the defence must prove that the accused was suffering from a
mental impairment at the time that s/he did the acts said to constitute the
relevant crime.
Second, the defence must prove that the mental impairment affected the
accused in one of two ways. It must have affected the accused in such a
way that s/he either did not know the nature and quality of what s/he
was doing, or s/he did not know that what s/he was doing was wrong.
If you find that the prosecution has proven, beyond reasonable doubt,
that [identify matters the prosecution must prove], and you are also
satisfied that both of these requirements have been proven by the
defence on the balance of probabilities, then this defence will be
successful and you must find NOA not guilty of that offence because of
mental impairment.
However, if the defence cannot prove, on the balance of probabilities,
both that NOA had a mental impairment at the relevant time, and that
the mental impairment affected him/her in one of the two ways I have
just mentioned, then this defence will fail. If you are also satisfied that all
of the elements of the offence have been proven by the prosecution,
beyond reasonable doubt, you should find NOA guilty of [insert offence].
I will now explain each of these requirements in more detail.
Mental Impairment
The first requirement that the defence must prove is that the accused
was suffering from a mental impairment at the time that s/he did the acts
said to constitute the crime of [insert offence].
The law does not define what “mental impairment” means. It is not a
psychiatric term with a specific medical definition. It is a term which
simply means a disease or illness of the mind. This includes [insert
relevant mental impairments].
[If there is evidence that the accused may have been suffering from a
temporary state of mind rather than a mental impairment, add the
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following shaded section.]
To satisfy this requirement, the accused must have been suffering from
some kind of mental illness or disorder, and not just from a temporary
state of mind such as impulsiveness or passion. This is not to suggest that
the mental impairment needs to be permanent – but it must be something
more than just a passing mental malfunction.
[If there is evidence that the accused’s mental impairment was caused by
an external factor, add the following shaded section.]
To satisfy this requirement, the mental impairment must have been
caused by something “internal” to the accused, as distinct from being the
result of an external physical factor, such as [insert relevant example].
In this case, the defence alleged that NOA was suffering from a mental
impairment when s/he [insert relevant acts and summary of evidence
and/or arguments]. The prosecution denied this, submitting [insert
summary of relevant evidence and/or arguments].
It is for you to decide, based on all of the evidence, if NOA was suffering
from a mental impairment at the relevant time. It is only if the defence
has proved that this was more likely than not that this first requirement
will be met.
Effect of the Mental Impairment
The second requirement that the defence must prove relates to the
effect of the mental impairment on the accused. The defence must prove
that the mental impairment affected him/her to such an extent that when
s/he committed the acts said to constitute the crime s/he either:

Did not know the nature and quality of what s/he was doing; or

Did not know that what s/he was doing was wrong.
The defence only needs to prove one of these effects, although in some
cases there may be evidence of both. I will look at each of them in turn.
Nature and Quality of the Act
The first way in which the defence can satisfy this requirement is by
proving, on the balance of probabilities, that the accused’s mental
impairment affected him/her to such an extent that s/he did not know the
nature and quality of what s/he was doing.
This means that because of his/her mental impairment, the accused was
unable to appreciate the physical nature and significance of what s/he was
doing when s/he committed the acts said to constitute the crime. The
accused was affected by his/her mental impairment in a way which led
him/her to believe s/he was doing one thing, when in reality s/he was
doing something completely different.
3
An example of this would be where a person thinks she is entering her
own house, when she is in fact breaking into Parliament House. Another
example would be a person who thinks that he is killing a rabbit, when in
reality he is killing one of his friends.
[If this limb is in issue, add the following shaded section.]
In this case the defence argued that NOA did not know the nature and
quality of what s/he was doing when [insert relevant acts and summary of
relevant evidence and/or arguments]. The prosecution responded [insert
relevant evidence and/or arguments].
[If this limb is not in issue, add the following shaded section.]
The defence has not sought to rely on this part of the second requirement,
instead alleging that NOA did not know that his/her actions were wrong.
Knowledge that NOA’s actions were wrong
The second way in which the defence can satisfy this requirement is by
proving, on the balance of probabilities, that when the accused committed
the acts said to constitute the crime, the mental impairment affected
him/her to such an extent that s/he did not know that what s/he was
doing was wrong.
The law defines this to mean that the accused could not reason with a
moderate degree of sense and composure about whether his/her conduct,
as perceived by reasonable people, was wrong.
You can see from this definition that the test is not whether the accused’s
acts were in fact wrong, or that accused knew that his/her actions were
wrong according to the law or morality. It is that the accused was not able
to reason in such a way that s/he would have known that reasonable
people would consider his/her conduct to be wrong. That is, there was
something so wrong with the accused’s mind due to his/her mental
impairment that s/he was incapable of realising that reasonable people
would think his/her behaviour was wrong.
[If this limb is in issue, add the following shaded section.]
In this case the defence argued that NOA did not know that what s/he was
doing was wrong when [insert relevant acts and summary of relevant
evidence and/or arguments]. The prosecution responded [insert relevant
evidence and/or arguments].
[If this limb is not in issue, add the following shaded section.]
The defence has not sought to rely on this part of the second requirement,
instead alleging that NOA did not know the nature and quality of what
s/he was doing.
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Summary, Possible Verdicts and Consequences
To summarise, you must first determine whether the prosecution has
proven, beyond reasonable doubt, [identify matters the prosecution must
prove]. If you are not satisfied that the prosecution has proven all of
these matters, then you must find NOA not guilty of that offence,
regardless of your views about his/her possible mental impairment. As
s/he will not have been convicted of that offence, that will be the end of
the legal process. S/he will be discharged and free to walk away from the
court.
If you decide that the prosecution has proven all of those matters beyond
reasonable doubt, you must then look at the defence of mental
impairment. You must determine whether the defence has proven, on the
balance of probabilities, that:

One – NOA had a mental impairment at the time s/he did the acts
said to constitute that offence; and

Two – that the mental impairment affected NOA in such a way that
when s/he committed the acts said to constitute the offence, s/he did
not know the nature and quality of what s/he was doing or s/he did
not know that what s/he was doing was wrong.
It is only if the accused has established both of these requirements on the
balance of probabilities that you may return a verdict of “not guilty
because of mental impairment”.
If that is your verdict, then there will be two options open to me. The
first is to declare that the accused is liable to a Supervision Order, and
the second is to order that s/he be released unconditionally. I would have
to form a view, based on the evidence, as to what was the appropriate
course to be followed.
A Supervision Order, which is the first option that would be open to me,
may commit the person to custody, or release the person on conditions
decided by the court and specified in the Order.
So you can see that there are different legal consequences that follow
from the different verdicts available to you. And you can see, as I have
told you, that a verdict of not guilty because of mental impairment has
quite different consequences from a verdict of not guilty.
Because of these different consequences, it is necessary for you to tell
me, if you reach a verdict of not guilty, whether you have reached that
verdict because of mental impairment or not.
Although I have just explained to you the possible consequences of the
different verdicts available in this case, it is important that you do not
take these consequences into account in making your determination. As I
told you earlier, you have an obligation to make your decision based on
the evidence in the case, not on irrelevant factors such as the
consequences of your decision.
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