News · Criminal law explainer
The De Simoni principle in sentencing.
When a person is sentenced, the facts the court uses matter as much as the charge. A long-standing principle stops the court punishing a person for a more serious offence than the one they actually face. It comes from the High Court decision in De Simoni. This note explains what the principle means and how it protects an accused at sentence.
By Aaron Kernaghan · Published 3 September 2026
The De Simoni principle is a sentencing rule from the High Court: a court cannot sentence a person for a more serious offence than the one they were convicted of. It means the court cannot take into account, as an aggravating factor, a circumstance that would have made the person guilty of a more serious offence than the one charged. It protects an accused from being punished for conduct they were not convicted of.
What is the De Simoni principle?
The principle, from the High Court decision in The Queen v De Simoni (1981) 147 CLR 383, is that a court sentencing an offender cannot take into account, as an aggravating factor, a circumstance that would have made the offender guilty of a more serious offence than the one for which they are being sentenced.
In short, the court sentences for the offence charged, on facts consistent with that offence, and cannot punish the person as if they had committed a worse crime that was not charged.
Why does it exist?
The principle protects a basic fairness. A person is entitled to be sentenced for the offence they were convicted of, not for a more serious one the prosecution did not charge or prove. If the court could sentence on facts that amount to a more serious offence, it would punish the person for something they never faced.
It also protects the value of the charge and the plea. A person who pleads to, or is convicted of, a particular offence should be sentenced within the bounds of that offence.
How does it work in practice?
In practice, the principle limits the facts the court can treat as aggravating. If a particular fact would have made the offence a more serious offence, the court cannot use that fact to increase the sentence for the lesser offence charged. The facts the court sentences on must stay within the offence.
This is why the agreed facts and the charge matter so much. Where a matter is resolved by charge negotiation to a lesser offence, the principle helps ensure the person is sentenced for that lesser offence, not the original one.
An example
Suppose a person is charged with a basic assault, not an aggravated form that requires a weapon. The court cannot sentence them on the basis that a weapon was used, because using a weapon would have made them guilty of the more serious, aggravated offence they were not charged with. The weapon cannot be used to aggravate the basic offence.
So the principle keeps the sentence tethered to the offence actually charged and proved. It is a real protection at sentence.
Why it matters to the defence
The principle is an important check that a lawyer uses to keep a sentence within proper bounds. It affects how the facts are framed, what can be put as aggravating, and how a negotiated set of facts is drafted. Getting the facts right is a large part of a good sentence.
It works alongside the other sentencing rules. Our notes on the section 21A factors and totality explain how the court structures a sentence within these limits.
Frequently asked.
What is the De Simoni principle?
A sentencing rule from the High Court that a court cannot take into account, as an aggravating factor, a circumstance that would have made the offender guilty of a more serious offence than the one they are being sentenced for.
Where does the De Simoni principle come from?
From the High Court decision in The Queen v De Simoni (1981) 147 CLR 383. It has been applied ever since as a limit on sentencing.
What does the principle protect?
The fairness that a person is sentenced for the offence they were convicted of, not for a more serious one that was not charged or proved. It stops punishment for conduct the person did not face.
How does it work in practice?
It limits the facts the court can treat as aggravating. A fact that would have made the offence more serious cannot be used to increase the sentence for the lesser offence charged.
Why does it matter to the defence?
It keeps a sentence within proper bounds. It affects how the facts are framed, what can be put as aggravating, and how a negotiated set of facts is drafted, which is a large part of a good sentence.
To speak to a criminal defence lawyer, call Aaron Kernaghan on 0421 717 019.
This article is written by Aaron Kernaghan, criminal defence lawyer at Good Legal Lawyers, as at 3 September 2026. It is commentary and reflects the personal opinion of the author only. It is not legal advice, it is not a substitute for advice on your own matter, and it does not purport to be accurate or complete. Any matter referred to may be before the court and any person charged is presumed innocent. For advice on a specific matter, contact Aaron Kernaghan on 0421 717 019 or contact the firm.
More criminal-law commentary by Aaron Kernaghan.
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