The Legal Defence of Mental Health or Cognitive Impairment in NSW

The tragic deaths of two young boys in the Blue Mountains region of New South Wales has raised more questions than answers, as their mother remains under police guard in hospital suffering from self-inflicted stab wounds.

Those questions include: is the mother responsible? If so, what would cause her to commit such unspeakable acts? Was she suffering from a mental illness? And if so, is she criminally responsible for her actions?

The Case

Two boys were fatally stabbed in their Blue Mountains home this past week, with their wounded but conscious mother found beside them. 

The situation has led police to believe the mother is responsible of the deaths of her sons, Ben aged 9 and Russell aged 11, who were found by their father their beds on the Faulconbridge property. 

Mr Smith, who did not live at the property, says his sons were typical of other kids their age and would never do anything to harm themselves. 

“Russell and Ben were happy, funny, outgoing boys, and were very much loved by their family and friends. Like boys their age, they loved sports, soccer, the Penrith Panthers, fishing, books, music, spending time with their friends and Max, their pup”, the distraught father stated.

Police entered the home on the afternoon of Tuesday, 10 September 2024 and examined the scene.

They say they will keep an ‘open mind’ regarding the fatal events, although they formally arrested the mother who was conveyed to Westmead Hospital in Sydney for treatment

In the past, Ms Smith had been known to local authorities for ‘minor matters’, but nothing that would indicate something as grave as what has transpired. 

Police are now attempting to piece together the events leading up to the deaths, including investigating the whereabouts of the boys and their mother on the day and whether drugs were involved. 

But the tragic incident has raised the possibility the mother may have been suffering from a mental illness at the time, such as to potentially bring the legal defence of mental 

The Legal Defence of Mental Health Impairment or Cognitive Impairment in NSW

The defence currently known as ‘mental health impairment or cognitive impairment’ was previously known as ‘the mental illness defence’, and in bygone days ‘the insanity defence’.

It is a complete defence to a criminal offence in New South Wales and, if established, leads to a ‘special verdict of act proven but not criminally responsible’.

The latest version of the defence was enacted on 27 March 2021, and is contained in section 28 of the Mental Health and Cognitive Impairment Forensic Provisions Act 2020 (NSW) (‘the Act’).

What does the law say?

Section 28 of the Act provides that a person is not criminally responsible for an offence if, at the time of carrying out the act constituting the offence, the person had a mental health impairment or a cognitive impairment, or both, that had the effect that the person:

• did not know the nature and quality of the act, or
• did not know that the act was wrong (that is, the person could not reason with a moderate degree of sense and composure about whether the act, as perceived by reasonable people, was wrong).

It makes clear that the question of whether a defendant had a mental health impairment or a cognitive impairment, or both, that had that effect is a question of fact. This means it is to be determined by the fact-finder in the case – whether that be a jury, or a judge sitting alone (without a jury) in a criminal trial, or a magistrate if the case is determined in the local court.

The section further stipulates that the defendant is presumed not to have a mental health impairment or cognitive impairment, or both, that had that effect until and unless the contrary is established.

What is a mental health impairment?

Section 4 of the Act states that a person is considered to have a mental health impairment if:

• the person has a temporary or ongoing disturbance of thought, mood, volition, perception or memory, 
• the disturbance would be regarded as significant for clinical diagnostic purposes, and
• the disturbance impairs the emotional wellbeing, judgment, or behaviour of the person.

It provides that mental health impairment may arise from any of the following disorders:

• an anxiety disorder,
• an affective disorder, including clinical depression and bipolar disorder,
• a psychotic disorder,
• a substance-induced mental disorder that is not temporary.

It makes clear the above is not an exhaustive list.

The section goes on to state that a person is not considered to have a mental health impairment if the condition is caused solely by:

• the temporary effect of ingesting a substance, or
• a substance use disorder.

What is a cognitive impairment?

Section 5 of the Act states that a person is considered to have a cognitive impairment if:

• the person has an ongoing impairment in adaptive functioning, 
• the person has an ongoing impairment in comprehension, reason, judgment, learning or memory, and
• the impairments result from damage to or dysfunction, developmental delay, or deterioration of the person’s brain or mind that may arise from a condition set out below or for other reasons.

It goes on to explain that a cognitive impairment may arise from any of the following conditions:

• intellectual disability,
• borderline intellectual functioning,
• dementia,
• an acquired brain injury,
• drug or alcohol-related brain damage, including foetal alcohol spectrum disorder,
• autism spectrum disorder.

It makes clear the above is not an exhaustive list.

How is the defence established?

In order to establish the defence, it must be proven ‘on the balance of probabilities’ (in other words, that it is more likely than not) that:

• The defendant suffered from a mental health impairment and/or cognitive impairment at the time of the conduct constituting the alleged offence, and
• The condition/s caused the defendant to either not know the nature and quality of their actions, or not know the actions were wrong.

If both of those matters are established to the required degree, the defendant will be entitled to a special verdict of not guilty by reason of mental health impairment or cognitive impairment.

Effect of a special verdict

Unlike a general not guilty verdict, a special verdict of act proven but not criminally responsible by reason of mental health or cognitive impairment does not necessarily lead to a person’s release into the community.

Rather, section 33 of the Act provides that following a special verdict, a court may order that the defendant:

• be remanded in custody until a further order is made under the section,
• be detained in the place and manner that the court thinks fit (including a mental health facility until released by due process of law,
• be unconditionally or conditionally released from custody, or
• be subjected to any other order/s the court thinks appropriate.

The section provides that, before ordering the person’s release from custody, the court may request a report from a forensic psychiatrist or other suitable mental health professional not involved in the person’s treatment, to determine whether the person is likely to seriously endanger themselves or others.

The court is not to order the person’s release unless satisfied, on the balance of probabilities, that no such risk exists.

Courts will often order the defendant to undergo (further) assessment and review under the Mental Health Act 2007, which can involve an indeterminate length of involuntary detention at a mental health facility.

Need legal assistance?

If you or a loved-one has been accused of a criminal offence in circumstances where a mental health condition may exist, call Sydney Criminal Lawyers anytime on (02) 9261 8881 to engage the services of a defence team with comprehensive knowledge of mental health laws and how they apply to criminal cases, and a proven track record of having cases dismissed on grounds of mental health.