Common Defences

Defence to criminal charges

To be guilty of any criminal charge, the prosecution must establish beyond reasonable doubt all of the elements of the offence/s charged. Each crime has a set of elements that the prosecution must establish before criminal liability can be proven.

Even where all the elements of the offence are made out, a person is not guilty of a charge if they can successfully argue they have a defence. Once a defence is raised it is ordinarily a matter for the prosecution to disprove that defence beyond reasonable doubt. For example if a person raises they acted in self defence, the prosecution must establish beyond reasonable doubt that they were not acting in self defence. All defences must be supported by evidence; that is there needs to be some evidentiary basis for the defence to be raised. Some common defences are outlined below.


Consent Mental Impairment
Duress Claim of Right
Self Defence Intoxication
Sudden or Extraordinary Emergency Honest and Reasonable Mistake



Consent can be both a defence and the absence of consent can be an element of the offence charged. For example for an accused person to be guilty of rape or indecent assault, the prosecution must prove beyond reasonable doubt that there was an absence of consent. The law defines consent as free agreement.

The Crimes Act 1958 (Vic) section 36(2) lists 12 circumstances in which a person does not consent. The section specifically states it is a non-exhaustive list. The legislation prescribes that a person does not consent where:

  1. A person submits because of force or fear of force
  2. A person submits because of fear of harm of any type, whether to that person, someone else or an animal
  3. A person submits because they are unlawfully detained
  4. The person is asleep or unconscious
  5. The person is so affected by drugs or alcohol to be incapable of consenting
  6. The person is so affected by drugs or alcohol to be incapable of withdrawing consent.


An act is committed under duress if it is committed due to a threat of physical harm if the act is not done. The defence of duress recognises that sometimes people commit offences to avoid a threatened harm/injury from a third person. Where duress is raised as a defence, the prosecution must eliminate any reasonable possibility that the accused acted under duress.

Mental impairment

The defence is mental impairment is governed by the Crimes (Mental Impairment and Unfitness to the Tried) Act 1997 (Vic). An alleged offender will have a defence of mental impairment available if at the time they committed the act, they were suffering from a mental impairment that had the effect that they either:

  1. Did not know the nature and quality of what they were doing; or
  2. Did not know that their conduct was wrong.

The question of mental impairment can be raised at any time prior to or during trial, and can be raised by either the defence or prosecution. ‘Mental impairment’ is not defined however certain conditions have been held by the Court to be diseases of the mind include schizophrenia, hyperglycaemia (caused by excessive blood sugar levels) and some cases of dissociation and epilepsy.


Self-defence arises where the accused person believed upon reasonable grounds that it was necessary in self-defence to do what they did. There are two elements to the offence:

  1. The accused must have believed at the time that the act was committed that what they were doing was necessary (even if mistaken, the belief must be genuine); and


  1. That belief must have been based on reasonable grounds. In determining whether reasonable grounds exist the Court will consider:


  1. The surrounding circumstances
  2. All facts within the accused person’s knowledge
  3. The relationship between the parties
  4. The prior conduct of the victim
  5. How proportionate the accused person’s response was to the threat perceived
  6. The failure to retreat

Once raised by the defence, the prosecution must disprove one of the above two elements or the accused person is entitled to be acquitted (found not guilty).

Claim of Right

A claim of right if a genuine belief held by a person that they have a claim over certain money or property. The defence is available to any person who takes property, either on their own behalf or on behalf of another, if they believe another person has a bona fide claim of right to the money or property in question. Once raised in evidence, the prosecution must negate the defence of claim of right beyond reasonable doubt.

Honest and Reasonable Mistake

The defence of honest and reasonable mistake applies only to strict liability offences (most commonly seen in driving charges such as driving while suspended or exceeding the speed limit). The defence can be raised where you honestly believed that you were acting lawfully when you committed the offence and that you would not have acted that way if you knew what you were doing was against the law. The mistake must be honest and the belief in the mistake must be reasonable.

Sudden or Extraordinary Emergency

This defence only applies to cases of homicide and is set out in section 9AI Crimes Act 1958 (Vic). For this defence to be successful you need to believe that the emergency involves a risk of death or really serious injury and that you believed your actions were the only reasonable actions in the situation.


Intoxication is addressed in both the Victorian legislation and the common law. Intoxication is generally not a defence but can have used to assess whether the required mental element is proven by the prosecution. Intoxication can impact upon whether you intended to commit a crime or whether you foresaw the consequences of your conduct.