LEARN ABOUT OTHER DEFENCES
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MISTAKE OF FACT
s24 Criminal Code 1899 provides a person who does an act under an honest and reasonable, but mistaken, belief in the existence of any state of things is not criminally responsible for the act to any greater extent than if the real state of things had been such as the person believed to exist.
How the defence works.
Although described as a defence, the onus is on the prosecution to prove beyond reasonable doubt that a person did not act on a mistake of fact.
The defence works by assuming the facts mistakenly believed are the actual facts. The law is applied to the mistaken facts. A person is only guilty if the mistaken facts prove the offence beyond reasonable doubt. In other words, the law substitutes the mistaken facts for the true facts for the purpose of determining guilt.
The elements of the defence are:
1. A mistake about a matter of fact.
A mistake of law is not a defence under any circumstances. Whether a defence is available will depend on the nature of the mistake. This can sometime be difficult.
Mistakes about the prevailing speed limit or the presence of a school zone are mistakes of law not mistakes of fact.
Mistakes about the speed a vehicle was travelling due to a faulty speedometer or the time being outside those for a school zone speed limit due to a slow watch are mistakes of fact and would afford a defence.
2. The mistake is honest.
This means the belief is genuinely held. Unless there is clear evidence to the contrary this element of the defence is easy to establish.
3. The mistake is reasonable.
This means that the person must have some reasonable basis for the belief. The focus is still on what the person believed. It is not necessary to establish that a theoretical reasonable person would hold the same belief.
Factors personal to a defendant can be taken into account when considering whether they had a reasonable basis for their mistaken belief including the information available to them (whether correct or not), any mental impairment, language difficulties or intoxication.
When the defence applies.
The defence of Mistake of Fact applies to all offences unless it is expressly excluded by the law.
The defence of Mistake of Fact can also operate in conjunction with other defences. For example, an honest and reasonable mistake that a person was armed with a dangerous weapon can be taken into account when determining a claim of self-defence.
The defence of Mistake of Fact is relevant to proof of a lack of consent for the criminal offence of Rape and other sexual assaults. The prosecution must prove there was no consent and that a defendant did not hold an honest and reasonable belief there was consent.
More – “Between a Rock Lobster and a Heartless Place”
The leading case on what amounts to a mistake of law and a mistake of fact involved a great injustice. The case of Ostrowski v Palmer  HCA 30 involved a rock lobster fisherman fined $28,000.00 for fishing in a restricted area. The fisherman argued, and it was accepted, he checked and was expressly told by the same Department that prosecuted him that he could operate in that area. In short he honestly and reasonably believed he could fish in the area.
The matter went to the High Court which (somewhat reluctantly) ruled the mistake was one of law and that there was no defence. The essence of the mistake was the legal designation of the area as restricted or otherwise.
For what little it was worth Justices Callinan and Heydon were scathing of the decision to prosecute the matter commenting (emphasis added):
“To do so [prosecute] in those, and the further circumstances that a conviction would result not only in the distress and opprobrium that any conviction carries, but also in the imposition of harsh mandatory penalties, has the appearance of an act of mindless oppression.”
The Sydney Morning Herald summed up the injustice perfectly with the headline, “Between a Rock Lobster and a Heartless Place”