Mistake of fact under the Griffith Code: Criminal Code s 24 (WA and Queensland) 

This supplement sits beside Fault elements: intention, knowledge, recklessness, negligence, and strict liability and Offence elements: actus reus and mens rea. Those articles explain that a mistake defence works differently depending on whether an offence sits in a Code jurisdiction or a common-law jurisdiction, and say the exact mechanics "must be checked in the specific provision." This is that provision, for Western Australia and Queensland.

What stays shared

Every Australian jurisdiction recognises, in some form, that a person who acts on a genuinely mistaken view of the facts may not deserve criminal liability for what they actually did. The underlying idea — an honest, reasonable belief in facts that would have made the conduct innocent — is portable. What is not portable is where that idea sits in the structure of criminal responsibility, and how far it reaches.

The Code excuse: Criminal Code s 24

Western Australia¹ and Queensland² each schedule a Criminal Code to their Criminal Code Act, and both Codes contain a s 24 in materially the same terms, reflecting their shared origin in the Griffith Code. Section 24 excuses a person who does or omits to do an act under an honest and reasonable, but mistaken, belief in the existence of any state of things, judging the act as if the believed state of things had been real.

Two features of s 24 matter more for problem-solving than the wording alone:

• It is a general excuse, not a strict-liability-only defence. Unlike the common law's honest-and-reasonable-mistake defence (confined to strict liability offences), s 24 is capable of applying across the Code to any offence, subject to the next point.
• It can be excluded. Section 24 itself says its operation can be displaced by the express or implied terms of the law creating the offence. An offence drafted to require actual knowledge, or one that expressly negatives a mistake excuse, is not affected by s 24 in the same way.

Contrast with the common law position

New South Wales, Victoria, and South Australia do not have a s 24. At common law, an honest and reasonable mistake of fact is recognised as a defence to strict liability offences specifically — the position most often associated with Proudman v Dayman (1941) 67 CLR 536 — rather than as a general excuse running across the whole of criminal law. A student moving a mistake argument from a Code jurisdiction into a common-law jurisdiction (or the reverse) is not just relabelling the same rule; the scope of what the excuse can reach is genuinely different.

Worked overlay example

Imagine a person in Western Australia takes an item from a shop believing, honestly and on reasonable grounds, that it had been given to them. Charged with an offence requiring a taking without the owner's consent, the accused wants to raise mistake of fact.

A structured answer would:

1. identify the Code and confirm it is WA's (or Queensland's) Criminal Code, not a common-law position;
2. locate the specific offence provision and check whether it expressly or impliedly excludes s 24;
3. state the s 24 test — an honest belief, that is also reasonable, in a state of things that would have made the conduct innocent;
4. apply the test to the facts as the accused believed them to be, not as they turned out to be; and
5. confirm the evidential and persuasive burden — the accused bears an evidential burden to point to the mistake, after which the prosecution must exclude it beyond reasonable doubt.

Self-check

Before treating a s 24 answer as complete, ask:

• Have I named the specific Code (WA or Qld) rather than treating "the Code" as one thing?
• Have I checked whether the offence provision excludes s 24?
• Have I kept the Code's general mistake excuse separate from the common law's strict-liability-only defence?
• Have I checked the current WA or Qld legislation portal for the current text of s 24, rather than relying on a quoted fragment?