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Mistake of Fact (ACT)

The defence of mistake of fact applies to offences of strict liability. In the ACT, this defence can also be relied on in respect of some other offences in some circumstances. It is contained in sections 35 and 36 of the Criminal Code 2002. This page deals with the defence of mistake of fact in the ACT.


Under section 35 of the Criminal Code, a person is not criminally responsible for an offence that has a fault element other than negligence if:

  • when they carried out the physical act they held a mistaken belief about, or were ignorant of, facts; and
  • the mistaken belief negates intention.

Under section 36 of the Criminal Code, a person is not criminally responsible for an offence that has no fault element if:

  • when carrying out the physical act, the accused considered whether or not facts existed and was under a mistaken belief about those facts; and
  • had the mistaken belief been correct, their conduct would not have been an offence.

Strict liability offences

A strict liability offence is an offence for which there is no fault element. A fault element is a mental state that the accused must be proven to have had in order to be found guilty. Examples are intention (which is required to prove a charge of murder) or recklessness (which is required to prove a charge of assault or sexual assault).

An offence that does not have a fault element is one that requires  the prosecution to prove only that the accused committed the physical elements of the offence. A lot of traffic offences are strict liability offences as are offences involving breaches of family violence orders and apprehended violence orders. These offences do not require that the accused intended or foresaw the commission of the offence; only that they committed the acts alleged in the circumstances alleged.

Strict liability offences in the ACT include:

How might mistake of fact be argued?

In the above examples, an accused person could rely on the defence of mistake of fact as follows.


A person was caught travelling at 70km/h in an area where the speed limit was 60km/h. According to their speedometer, they were travelling at 60km/h. The accused in this situation could argue that they reasonably believed their speedometer to be accurate. In this example, the defence would not succeed if the person had been travelling at 100 km/h as a belief that they were not speeding in that situation would not be reasonable.

Breach AVO

A person was charged with breaching a family violence order. The order had a condition that the accused must not attend any premises where the protected person was living or working. The accused was found present at premises where the protected person was working. The accused could rely on a mistaken belief that the protected person did not work at the premises if the accused had reason to belief this was the case.

Child sex offences

A person was charged with having sex with a child under 16. The child in question was 15 and had told the accused they were 16. The accused could rely on an honest but mistaken belief that the child was over 16. This defence would be less likely to succeed the younger the child actually was as the mistake must be reasonable as well as honest.

Mistake of law is not a defence

It is important to note that the defence of mistake of fact does not apply to mistakes of law. If an accused person is mistaken about the law, this does not excuse them from responsibility for an offence. If a person is mistaken about a circumstance this is a combination of fact and law, this is taken to be a mistake of law.

Case law on mistake of fact

The defence of mistake of fact has been considered in a number of court decisions. Some of these are summarized below.

Proudman v Dayman (1941)

This decision established that the accused’s mistaken belief must be a positive belief and not mere ignorance.

He Kaw Te v The Queen (1985)

This decision further established that the accused must have expressly turned their mind to a particular fact and made the mistake. It is not enough that they simply did not consider the matter at all.

Mei Ying Su and Others v Australian Fisheries Management Authority and Another (2008)

This decision established that the defence of mistake of fact does not require the application of the ‘ordinary person’ test. It requires that the belief be a belief of the accused’s and that it be objectively reasonable. Reasonableness is to be assessed in relation to the accused’ subjective circumstances  including their personal attributes and the information they had at the time.

If you require legal advice or representation in any legal matter, please contact Go To Court Lawyers.

Fernanda Dahlstrom

This article was written by Fernanda Dahlstrom

Fernanda Dahlstrom has a Bachelor of Laws, a Bachelor of Arts and a Graduate Diploma in Legal Practice. She has also completed a Master’s in Writing and Literature. Fernanda practised law for eight years, working in criminal defence, child protection and domestic violence law in the Northern Territory and in family law in Queensland.

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