Complicity and accessorial liability 

Criminal liability is not confined to the person whose act completes the offence. A person who helps, encourages or agrees with the principal may be liable for the same offence, and Australian law provides several distinct routes to that result. They are not interchangeable, and a problem question usually rewards identifying which one the facts actually engage.

Accessorial liability: aiding, abetting, counselling, procuring

The classical form. An accessory is liable where they assisted or encouraged the principal offender, with knowledge of the essential facts constituting the offence and an intention that their conduct assist or encourage it.

Two points cause difficulty. First, presence is not participation: mere presence at the scene, even accompanied by approval, is not enough unless it in fact encouraged the principal or the accused had a duty to intervene. Second, the accessory must know the essential facts, not the legal characterisation — they need not know the conduct amounts to a crime, but must know what the principal is going to do in its material respects.

The accessory's liability is derivative: it depends on the principal offence having been committed, though the principal need not be convicted, and may be acquitted for reasons personal to them.

Joint criminal enterprise

Where two or more people agree to commit an offence and it is committed while the agreement is on foot, each participant is liable as a principal. The agreement need not be express or planned in advance; it may be inferred from conduct and may be formed on the spot.

The difference from accessorial liability matters. A participant in a joint criminal enterprise is liable for the agreed crime as a principal, not as a derivative party, and their liability does not depend on proof that they personally assisted.

Extended joint criminal enterprise

The extended form reaches an incidental crime — one outside the agreement but committed in carrying it out. A participant is liable where they foresaw the possibility that a co-venturer might commit the incidental offence and continued in the enterprise regardless.

This doctrine has been contentious, because foresight of a possibility is a lower fault standard than that required of the principal. The United Kingdom Supreme Court departed from it; in Miller v The Queen (2016) 259 CLR 380 the High Court declined to follow suit, and it remains part of Australian common law.¹ Where an armed robbery is agreed and a co-venturer kills, extended joint criminal enterprise is the route by which the other participants may be liable for the homicide.

Mitchell v The King (2023) 276 CLR 299; [2023] HCA 5² limits how far the doctrine reaches. All seven Justices held that extended joint criminal enterprise cannot be combined with s 12A of the Criminal Law Consolidation Act 1935 (SA), the statutory form of constructive murder, to create a further pathway to murder: Kiefel CJ at [30], Gageler, Gleeson and Jagot JJ at [43]-[47], and Gordon, Edelman and Steward JJ at [52]. Gordon, Edelman and Steward JJ, applying Miller, said that what must be foreseen is the incidental crime, being all of its elements: for murder, that death or really serious bodily injury might be occasioned by a co-venturer acting with murderous intention ([56]-[58]). A participant who foresees only the elements of a lesser crime can, under the doctrine, be convicted of that lesser crime and not the greater, for example manslaughter ([60]). Attribute the foresight statements to those three Justices, and the holding that the doctrine cannot be combined with s 12A, which turned on a South Australian statute, to the Court.

Commonwealth offences are statutory

For Commonwealth offences, Part 2.4 of the Criminal Code displaces the common law.³ Section 11.2 covers complicity and common purpose; s 11.2A provides for joint commission; s 11.3 for commission by proxy through an innocent agent; and s 11.4 for incitement. The fault elements are specified rather than inherited, and the Code's structure of physical and fault elements applies. Do not import common law joint criminal enterprise reasoning into a Commonwealth charge.

The state Code jurisdictions have their own parallel provisions, and the common law continues to govern in the common law states. Identify the source before applying any test.

Withdrawal

A participant may escape liability by withdrawing, but the requirements are strict and increase with the extent of their involvement. Communication of withdrawal to the other participants is ordinarily essential, it must be timely — before the offence is committed — and it must be unequivocal. Where the accused has supplied the means, more is required: reasonable steps to undo the assistance, which may extend to warning the intended victim or alerting police. A change of heart that is never communicated achieves nothing.

Innocent agents and procuring

A person who brings about an offence through someone who is not themselves criminally liable — a child below the age of responsibility, a person acting under a mistake induced by the accused, or a person lacking the required fault element — is liable as a principal through the doctrine of the innocent agent, not as an accessory.

The distinction matters because accessorial liability requires that the principal offence be committed by someone. Where the person who performed the act is not liable at all, there is no principal offence to be accessory to, and the doctrine of innocent agency supplies the answer.

Accessory after the fact

Distinct from the forms of complicity above, an accessory after the fact is a person who, knowing an offence has been committed, assists the offender to escape apprehension, prosecution or punishment. It is a separate offence with its own penalty, generally lower than that for the principal offence.

The key differences: the assistance comes after the offence is complete, so it cannot have contributed to it; and knowledge of the offence, not merely suspicion, must be proved. Several jurisdictions exempt spouses and close family members from liability.

Liability where the principal is not convicted

An accessory may be convicted even though the principal has been acquitted, has not been identified, or has never been prosecuted. What must be proved is that the principal offence was committed, not that somebody was convicted of it.

The acquittal of the principal in separate proceedings does not create an issue estoppel in the accessory's trial, since issue estoppel does not operate in criminal proceedings.

An accessory may also be convicted of a more serious offence than the principal where their own fault element is higher — the classic case being an accessory who intends death assisting a principal convicted only of manslaughter.

Sentencing accessories

There is no rule that an accessory receives a lesser sentence. Culpability is assessed on the accessory's own role and state of mind, and an organiser who never attends the scene may be sentenced more severely than the person who performed the act.

Relevant factors include the significance of the contribution, whether the accessory instigated or merely acquiesced, the degree of foresight, and any attempt at withdrawal falling short of the legal requirements — which is not a defence but is mitigating.

Applying this in a problem question

1. Identify the jurisdiction and whether the offence is Commonwealth, Code or common law, because that selects the governing scheme.
2. Establish what the principal offender did, since accessorial liability is derivative.
3. Choose the route the facts support — assistance or encouragement, an agreement, or an incidental crime committed in carrying out an agreement — and apply that route's own test.
4. For extended joint criminal enterprise, state the fault element precisely: foresight of the possibility, not intention.
5. Deal with withdrawal expressly if the accused had second thoughts, and test communication, timing and whether the assistance was undone.

Self-check

• Have I identified whether the Code or the common law governs before applying a test?
• Have I avoided treating mere presence as participation?
• Have I kept joint criminal enterprise separate from accessorial liability?
• Have I applied the correct fault standard to the incidental offence?