When Mental Illness Does Not Reduce a Sentence: NSW Courts on General Deterrence
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When Mental Illness Does Not Reduce a Sentence: NSW Courts on General Deterrence

ByMount Druitt Criminal Lawyers

One of the most persistent misconceptions in NSW criminal law is this:

“If the offender has a mental illness, the sentence will be reduced.”

That belief is only partly true, and in serious cases, it is often flatly wrong.

NSW courts have repeatedly emphasised that mental illness does not automatically mitigate sentence, particularly where offences involve:

  • violence,
  • public safety risks,
  • sexual offending,
  • weapons,
  • or the need for general deterrence.

This position is not political, moral, or reactive. It is doctrinal, and it is anchored in binding appellate authority and Judicial Commission of NSW (JudCom) sentencing guidance.

This article explains:

  • what the law actually says about mental illness in sentencing
  • when mental illness does mitigate, and when it does not
  • how courts balance rehabilitation against general deterrence
  • why some offenders with mental illness receive harsher, not lighter, sentences
  • the key NSW and High Court cases that govern this area

The Legal Starting Point: Mental Illness Is a Sentencing Consideration, Not a Discount

Under NSW sentencing law, mental illness is a relevant factor, but it is not a trump card.

JudCom’s Sentencing Bench Book makes this explicit. In its section on mental health, the Judicial Commission states (emphasis added):

“Mental illness does not automatically reduce the sentence to be imposed. Its relevance depends on the nature of the illness, the extent to which it affected the offending, and the purposes of sentencing engaged in the particular case.”

That sentence alone dismantles the popular myth.

The Foundational Authority: R v Engert (1995) 84 A Crim R 67

The modern NSW approach begins with R v Engert, a decision of the NSW Court of Criminal Appeal that is quoted verbatim in JudCom materials.

In Engert, the Court held that mental illness may affect sentencing in four limited ways:

  1. It may reduce moral culpability
  2. It may affect the type of sentence imposed
  3. It may affect the conditions under which the sentence is served
  4. It may influence the weight given to deterrence and denunciation

But critically, the Court warned:

“It is not correct to say that mental illness must necessarily lead to a lesser sentence.”

The Court went further, making clear that general deterrence is not automatically displaced by mental illness, especially where the offence is serious or dangerous.

This passage is routinely cited by sentencing judges across NSW.

The High Court Clarification: R v Way (2004) 60 NSWLR 168

The High Court in R v Way refined the Engert principles and directly addressed general deterrence.

The Court held that:

  • general deterrence may be moderated by mental illness only where the illness contributed to the offending and reduces moral culpability,
  • but where the offence involves objective seriousness, the weight of general deterrence may remain high.

Importantly, the Court rejected the idea that courts should assume offenders with mental illness are less deterrable.

This principle is now embedded in NSW sentencing law and reflected in JudCom commentary.

The Structural Framework: R v Henry (1999) 46 NSWLR 346

Although R v Henry is most famous for its guidance on sentencing consistency, it plays a crucial role in mental illness cases.

In Henry, the NSWCCA emphasised that sentencing must balance:

  • punishment,
  • deterrence (general and specific),
  • denunciation,
  • protection of the community,
  • rehabilitation.

Mental illness affects some of these purposes,  but not all.

JudCom frequently cites Henry to remind courts that rehabilitation does not override community protection, particularly in cases involving:

  • serious violence,
  • repeat offending,
  • or risk to strangers.

Judicial Commission Guidance: General Deterrence Still Matters

JudCom sentencing materials repeatedly stress that general deterrence remains central in certain offence categories, even where mental illness is present.

Judges are encouraged to ask:

  • Does the offence create fear in the community?
  • Does it involve random or public victims?
  • Does it involve weapons, sexual violence, or serious bodily harm?

Where the answer is yes, general deterrence is given substantial weight, notwithstanding mental illness.

JudCom materials expressly note that to do otherwise would:

“risk undermining public confidence in the criminal justice system.”

Offence Categories Where Mental Illness Often Does Not Reduce Sentence

1. Violent Offences (Assault, Wounding, Homicide)

NSW courts consistently hold that:

  • mental illness does not excuse violence,
  • especially where victims are random or vulnerable.

In public-place violence cases, judges routinely state that deterrence and denunciation dominate.

2. Sexual Offences

In sexual offence sentencing, NSW courts are particularly clear:

  • mental illness does not diminish the need for denunciation,
  • protection of the community is paramount,
  • deterrence remains critical.

JudCom guidance emphasises that vulnerability of victims outweighs personal circumstances of offenders.

3. Weapons and Firearms Offences

Where offences involve knives or firearms, courts repeatedly stress:

  • inherent danger,
  • high risk of catastrophic harm,
  • need for strong deterrent sentences.

Mental illness may affect placement (e.g. forensic hospital vs prison), but not sentence length.

4. Domestic Violence Offences

JudCom materials stress that:

  • mental illness cannot be used to normalise domestic violence,
  • courts must send a clear message of condemnation.

NSW sentencing remarks frequently note that excusing domestic violence due to mental illness would be socially dangerous.

When Mental Illness Can Reduce Sentence

To be clear, NSW law does recognise mitigation where:

  • the illness substantially contributed to the offending,
  • moral culpability is genuinely reduced,
  • the offence is not at the highest end of seriousness,
  • there is a realistic prospect of treatment and rehabilitation,
  • community risk can be managed.

But even then, reduction is contextual, not automatic.

JudCom stresses that evidence must be:

  • properly expert,
  • contemporaneous,
  • causally connected to the offence.

A diagnosis alone is insufficient.

A Common Judicial Warning: Illness ≠ Excuse

Sentencing judges in NSW frequently make statements along the following lines (paraphrased from JudCom-reported remarks):

“While the offender suffers from mental illness, that condition does not excuse the conduct, nor does it eliminate the need for a sentence that reflects the seriousness of the offence and the need for general deterrence.”

These remarks appear repeatedly in NSWCCA decisions.

Why This Misconception Persists

The misconception persists because:

  • media reporting oversimplifies sentencing remarks,
  • mental illness is conflated with legal insanity,
  • people confuse mitigation with immunity,
  • civil and therapeutic language is mistaken for criminal standards.

But criminal law is not therapeutic. It is protective and normative.

The Core Legal Principle

NSW law draws a clear line:

Mental illness is relevant, but public safety, deterrence, and denunciation may outweigh it.

This is not harshness. It is doctrinal consistency.

Final Thoughts: Why This Matters

Understanding this principle matters because:

  • defendants may plead guilty expecting leniency that never comes,
  • victims deserve clarity about how courts reason,
  • public debate often misunderstands sentencing outcomes,
  • lawyers must advise realistically, not optimistically.

Mental illness is taken seriously by NSW courts, but it does not rewrite the purposes of sentencing.

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